DISTRIBUTION STATEMENT A: Approved for public release; distribution is unlimited.

NONRESIDENT

TRAININGCOURSE

May 1994

Blueprint Readingand SketchingNAVEDTRA 14040

COMMANDING OFFICERNETPDTC

6490 SAUFLEY FIELD RDPENSACOLA, FL 32509-5237

ERRATA #1 19 Oct 1998

Specific Instructions and Errata forNonresident Training Course

BLUEPRINT READING AND SKETCHING

1. No attempt has been made to issue corrections for errorsin typing, punctuation, etc., that do not affect yourability to answer the question or questions.

2. To receive credit for deleted questions, show thiserrata to your local course administrator (ESO/scorer).The local course administrator is directed to correct thecourse and the answer key by indicating the questiondeleted.

3. Assignment Booklet

Delete the following questions, and leave the correspondingspaces blank on the answer sheets:

Questions

1-211-222-483-284-214-344-62

iPREFACEBy enrolling in this self-study course, you have demonstrated a desire to improve yourself and the Navy.Remember, however, this self-study course is only one part of the total Navy training program. Practicalexperience, schools, selected reading, and your desire to succeed are also necessary to successfully roundout a fully meaningful training program.

COURSE OVERVIEW: Upon completing this nonresident training course, you should understand thebasics of blueprint reading including projections and views, technical sketching, and the use of blueprints inthe construction of machines, piping, electrical and electronic systems, architecture, structural steel, andsheet metal.

THE COURSE: This self-study course is organized into subject matter areas, each containing learningobjectives to help you determine what you should learn along with text and illustrations to help youunderstand the information. The subject matter reflects day-to-day requirements and experiences ofpersonnel in the rating or skill area. It also reflects guidance provided by Enlisted Community Managers(ECMs) and other senior personnel, technical references, instructions, etc., and either the occupational ornaval standards, which are listed in the Manual of Navy Enlisted Manpower Personnel Classificationsand Occupational Standards, NAVPERS 18068.

THE QUESTIONS: The questions that appear in this course are designed to help you understand thematerial in the text.

VALUE: In completing this course, you will improve your military and professional knowledge.Importantly, it can also help you study for the Navy-wide advancement in rate examination. If you arestudying and discover a reference in the text to another publication for further information, look it up.

1994 Edition Prepared byMMC(SW) D. S. Gunderson

Published byNAVAL EDUCATION AND TRAINING

PROFESSIONAL DEVELOPMENTAND TECHNOLOGY CENTER

NAVSUP Logistics Tracking Number0504-LP-026-7150

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Sailors Creed

I am a United States Sailor.

I will support and defend theConstitution of the United States ofAmerica and I will obey the ordersof those appointed over me.

I represent the fighting spirit of theNavy and those who have gonebefore me to defend freedom anddemocracy around the world.

I proudly serve my countrys Navycombat team with honor, courageand commitment.

I am committed to excellence andthe fair treatment of all.

CONTENTS

CHAPTER PAGE1. Blueprint Reading . . . . . . . . . . . . . . . . . . . . . . . . . . 1-12. Technical Sketching . . . . . . . . . . . . . . . . . . . . . . . . . 2-13. Projections and Views . . . . . . . . . . . . . . . . . . . . . . . . 3-14. Machine Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15. Piping Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-16. Electrical and Electronics Prints . . . . . . . . . . . . . . . . . . . 6-17. Architectural and Structural Steel Drawings . . . . . . . . . . . . . 7-18. Developments and Intersections . . . . . . . . . . . . . . . . . . . 8-1

APPENDIXI. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AI-1

II. Graphic Symbols for Aircraft Hydraulic andPneumatic Systems . . . . . . . . . . . . . . . . . . . . . . . . AII-1

III. Graphic Symbols for Electrical and Electronics Diagrams . . . AIII-1IV.

Deleted. . . . . . . . . . . . . . . . . . . . . . . . . . . .AIV-1V. References Used to Develop the TRAMAN . . . . . . . . . . . . AV-1

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INDEX-1

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INSTRUCTIONS FOR TAKING THE COURSE

ASSIGNMENTS The text pages that you are to study are listed at the beginning of each assignment. Study these pages carefully before attempting to answer the questions. Pay close attention to tables and illustrations and read the learning objectives. The learning objectives state what you should be able to do after studying the material. Answering the questions correctly helps you accomplish the objectives. SELECTING YOUR ANSWERS Read each question carefully, then select the BEST answer. You may refer freely to the text. The answers must be the result of your own work and decisions. You are prohibited from referring to or copying the answers of others and from giving answers to anyone else taking the course. SUBMITTING YOUR ASSIGNMENTS To have your assignments graded, you must be enrolled in the course with the Nonresident Training Course Administration Branch at the Naval Education and Training Professional Development and Technology Center (NETPDTC). Following enrollment, there are two ways of having your assignments graded: (1) use the Internet to submit your assignments as you complete them, or (2) send all the assignments at one time by mail to NETPDTC. Grading on the Internet: Advantages to Internet grading are: you may submit your answers as soon as

you complete an assignment, and you get your results faster; usually by the

next working day (approximately 24 hours). In addition to receiving grade results for each assignment, you will receive course completion confirmation once you have completed all the

assignments. To submit your assignment answers via the Internet, go to:

http://courses.cnet.navy.mil

Grading by Mail: When you submit answer sheets by mail, send all of your assignments at one time. Do NOT submit individual answer sheets for grading. Mail all of your assignments in an envelope, which you either provide yourself or obtain from your nearest Educational Services Officer (ESO). Submit answer sheets to:

COMMANDING OFFICER NETPDTC N331 6490 SAUFLEY FIELD ROAD PENSACOLA FL 32559-5000

Answer Sheets: All courses include one scannable answer sheet for each assignment. These answer sheets are preprinted with your SSN, name, assignment number, and course number. Explanations for completing the answer sheets are on the answer sheet. Do not use answer sheet reproductions: Use only the original answer sheets that we providereproductions will not work with our scanning equipment and cannot be processed. Follow the instructions for marking your answers on the answer sheet. Be sure that blocks 1, 2, and 3 are filled in correctly. This information is necessary for your course to be properly processed and for you to receive credit for your work. COMPLETION TIME Courses must be completed within 12 months from the date of enrollment. This includes time required to resubmit failed assignments.

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PASS/FAIL ASSIGNMENT PROCEDURES If your overall course score is 3.2 or higher, you will pass the course and will not be required to resubmit assignments. Once your assignments have been graded you will receive course completion confirmation. If you receive less than a 3.2 on any assignment and your overall course score is below 3.2, you will be given the opportunity to resubmit failed assignments. You may resubmit failed assignments only once. Internet students will receive notification when they have failed an assignment--they may then resubmit failed assignments on the web site. Internet students may view and print results for failed assignments from the web site. Students who submit by mail will receive a failing result letter and a new answer sheet for resubmission of each failed assignment. COMPLETION CONFIRMATION After successfully completing this course, you will receive a letter of completion. ERRATA Errata are used to correct minor errors or delete obsolete information in a course. Errata may also be used to provide instructions to the student. If a course has an errata, it will be included as the first page(s) after the front cover. Errata for all courses can be accessed and viewed/downloaded at: http://www.advancement.cnet.navy.mil STUDENT FEEDBACK QUESTIONS We value your suggestions, questions, and criticisms on our courses. If you would like to communicate with us regarding this course, we encourage you, if possible, to use e-mail. If you write or fax, please use a copy of the Student Comment form that follows this page.

For subject matter questions: E-mail: n314.products@cnet.navy.mil Phone: Comm: (850) 452-1001, Ext. 1826 DSN: 922-1001, Ext. 1826 FAX: (850) 452-1370 (Do not fax answer sheets.) Address: COMMANDING OFFICER NETPDTC N314 6490 SAUFLEY FIELD ROAD PENSACOLA FL 32509-5237 For enrollment, shipping, grading, or completion letter questions E-mail: fleetservices@cnet.navy.mil Phone: Toll Free: 877-264-8583 Comm: (850) 452-1511/1181/1859 DSN: 922-1511/1181/1859 FAX: (850) 452-1370 (Do not fax answer sheets.) Address: COMMANDING OFFICER NETPDTC N331 6490 SAUFLEY FIELD ROAD PENSACOLA FL 32559-5000 NAVAL RESERVE RETIREMENT CREDIT

If you are a member of the Naval Reserve, you may earn retirement points for successfully completing this course, if authorized under current directives governing retirement of Naval Reserve personnel. For Naval Reserve retire-ment, this course is evaluated at 6 points. (Refer to Administrative Procedures for Naval Reservists on Inactive Duty, BUPERSINST 1001.39, for more information about retirement points.)

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Student Comments Course Title: Blueprint Reading and Sketching

NAVEDTRA: 14040 Date: We need some information about you: Rate/Rank and Name: SSN: Command/Unit Street Address: City: State/FPO: Zip Your comments, suggestions, etc.: Privacy Act Statement: Under authority of Title 5, USC 301, information regarding your military status is requested in processing your comments and in preparing a reply. This information will not be divulged without written authorization to anyone other than those within DOD for official use in determining performance. NETPDTC 1550/41 (Rev 4-00

CHAPTER 1

BLUEPRINTS

When you have read and understood this chapter,you should be able to answer the following learningobjectives:

Describe blueprints and how they are pro-duced.Identify the information contained in blue-prints.

Explain the proper filing of blueprints.Blueprints (prints) are copies of mechanical or

other types of technical drawings. The term blueprintreading, means interpreting ideas expressed by otherson drawings, whether or not the drawings are actuallyblueprints. Drawing or sketching is the universallanguage used by engineers, technicians, and skilledcraftsmen. Drawings need to convey all the necessaryinformation to the person who will make or assemblethe object in the drawing. Blueprints show theconstruction details of parts, machines, ships, aircraft,buildings, bridges, roads, and so forth.

BLUEPRINT PRODUCTION

Original drawings are drawn, or traced, directly ontranslucent tracing paper or cloth, using black water-proof India ink, a pencil, or computer aided drafting(CAD) systems. The original drawing is a tracing ormaster copy. These copies are rarely, if ever, sent toa shop or site. Instead, copies of the tracings are givento persons or offices where needed. Tracings that areproperly handled and stored will last indefinitely.

The term blueprint is used loosely to describecopies of original drawings or tracings. One of the firstprocesses developed to duplicate tracings producedwhite lines on a blue background; hence the termblueprint. Today, however, other methods produceprints of different colors. The colors may be brown,black, gray, or maroon. The differences are in thetypes of paper and developing processes used.

A patented paper identified as BW paper producesprints with black lines on a white background. Thediazo, or ammonia process, produces prints with eitherblack, blue, or maroon lines on a white background.

Another type of duplicating process rarely used toreproduce working drawings is the photostatic processin which a large camera reduces or enlarges a tracingor drawing. The photostat has white lines on a darkbackground. Businesses use this process to incor-porate reduced-size drawings into reports or records.

The standards and procedures prescribed formilitary drawings and blueprints are stated in militarystandards (MIL-STD) and American National Stan-dards Institute (ANSI) standards. The Department ofDefense Index of Specifications and Standards liststhese standards; it is issued on 31 July of each year.The following list contains common MIL-STD andANSI standards, listed by number and title, thatconcern engineering drawings and blueprints.

Number

MIL-STD-100AANSI Y14.5M-1982MIL-STD-9A

ANSI 46.1-1962MIL-STD-12CMIL-STD-14AANSI Y32.2

MIL-STD-15

ANSI Y32.9

MIL-STD-16C

MIL-STD-17B, Part 1MIL-STD-17B, Part 2

MIL-STD-18BMIL-STD-21A

MIL-STD-22AMIL-STD-25A

Title

Engineering Drawing PracticesDimensioning and TolerancingScrew Thread Conventions andMethods of SpecifyingSurface TextureAbbreviations for Use on DrawingsArchitectural SymbolsGraphic Symbols for Electrical andElectronic DiagramsElectrical Wiring Part 2, and Equip-ment Symbols for Ships and Plans,Part 2Electrical Wiring Symbols forArchitectural and Electrical LayoutDrawingsElectrical and Electronic ReferenceDesignationsMechanical SymbolsMechanical Symbols for Aeronautical,Aerospace craft and Spacecraft useStructural SymbolsWelded-Joint Designs, Armored-TankTypeWelded Joint DesignsNomenclature and Symbols for ShipStructure

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PARTS OF A BLUEPRINTMIL-STD-100A specifies the size, format, loca-

tion, and type of information that should be includedin military blueprints. These include the informationblocks, finish marks, notes, specifications, legends,and symbols you may find on a blueprint, and whichare discussed in the following paragraphs.

INFORMATION BLOCKS

The draftsman uses information blocks to give thereader additional information about materials,specifications, and so forth that are not shown in the

blueprint or that may need additional explanation. Thedraftsman may leave some blocks blank if theinformation in that block is not needed. The followingparagraphs contain examples of information blocks.

Title BlockThe title block is located in the lower-right corner

of all blueprints and drawings prepared according toMIL-STDs. It contains the drawing number, name ofthe part or assembly that it represents, and all informa-tion required to identify the part or assembly.

It also includes the name and address of the govem-ment agency or organization preparing the drawing,

Figure 1-1.Blueprint title blocks. (A) Naval Ship Systems Command; (B) Naval Facilities Engineering Command.

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the scale, drafting record, authentication, and date(fig. 1-1).

A space within the title block with a diagonal orslant line drawn across it shows that the informationis not required or is given elsewhere on the drawing.

Revision Block

If a revision has been made, the revision block willbe in the upper right corner of the blueprint, as shownin figure 1-2. All revisions in this block are identified

Figure 1-2.Electrical plan.

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by a letter and a brief description of the revision. Arevised drawing is shown by the addition of a letter tothe original number, as in figure 1-1, view A. When theprint is revised, the letter A in the revision block isreplaced by the letter B and so forth.

Drawing Number

Each blueprint has a drawing number (fig. 1-1,views A and B), which appears in a block in the lowerright corner of the title block. The drawing number canbe shown in other places, for example, near the topborder line in the upper corner, or on the reverse sideat the other end so it will be visible when the drawingis rolled. On blueprints with more than one sheet, theinformation in the number block shows the sheetnumber and the number of sheets in the series. Forexample, note that the title blocks shown in figure 1-1,show sheet 1 of 1.

Reference Number

Reference numbers that appear in the title blockrefer to numbers of other blueprints. A dash and anumber show that more than one detail is shown on adrawing. When two parts are shown in one detaildrawing, the print will have the drawing number plusa dash and an individual number. An example is thenumber 811709-1 in the lower right corner of figure1-2.

In addition to appearing in the title block, the dashand number may appear on the face of the drawingsnear the parts they identify. Some commercial printsuse a leader line to show the drawing and dash numberof the part. Others use a circle 3/8 inch in diameteraround the dash number, and carry a leader line to thepart.

A dash and number identify changed or improvedparts and right-hand and left-hand parts. Many aircraftparts on the left-hand side of an aircraft are mirrorimages of the corresponding parts on the right-handside. The left-hand part is usually shown in thedrawing.

On some prints you may see a notation above thetitle block such as 159674 LH shown; 159674-1 RHopposite. Both parts carry the same number. LHmeans left hand, and RH means right hand. Somecompanies use odd numbers for right-hand parts andeven numbers for left-hand parts.

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Zone Number

Zone numbers serve the same purpose as thenumbers and letters printed on borders of maps to helpyou locate a particular point or part. To find a point orpart, you should mentally draw horizontal and verticallines from these letters and numerals. These lines willintersect at the point or part you are looking for.

You will use practically the same system to helpyou locate parts, sections, and views on largeblueprinted objects (for example, assembly drawingsof aircraft). Parts numbered in the title block are foundby looking up the numbers in squares along the lowerborder. Read zone numbers from right to left.

Scale Block

The scale block in the title block of the blueprintshows the size of the drawing compared withthe actual size of the part. The scale may be shown as1 = 2, 1 = 12, 1/2 = 1, and so forth. It also maybe shown as full size, one-half size, one-fourth size,and so forth. See the examples in figure 1-1, views Aand B.

If the scale is shown as 1 = 2, each line on theprint is shown one-half its actual length. If a scale isshown as 3 = 1, each line on the print is three timesits actual length.

The scale is chosen to fit the object being drawnand space available on a sheet of drawing paper.

Never measure a drawing; use dimensions. Theprint may have been reduced in size from the originaldrawing. Or, you might not take the scale of thedrawing into consideration. Paper stretches andshrinks as the humidity changes. Read the dimensionson the drawing; they always remain the same.

Graphical scales on maps and plot plans show thenumber of feet or miles represented by an inch.A fraction such as 1/500 means that one unit on themap is equal to 500 like units on the ground. A largescale map has a scale of 1 = 10; a map with a scaleof 1 = 1000 is a small scale map. The followingchapters of this manual have more information on thedifferent types of scales used in technical drawings.

Station Number

A station on an aircraft may be described as a rib(fig. 1-3). Aircraft drawings use various systems ofstation markings. For example, the centerline of the

Figure 1-3.Aircraft stations and frames.

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aircraft on one drawing may be taken as the zerostation. Objects to the right or left of center along thewings or stabilizers are found by giving the number ofinches between them and the centerline zero station.On other drawings, the zero station may be at the noseof the fuselage, at a firewall, or at some other locationdepending on the purpose of the drawing. Figure 1-3shows station numbers for a typical aircraft.

Bill of Material

The bill of material block contains a list of theparts and/or material needed for the project. The blockidentifies parts and materials by stock number or otherappropriate number, and lists the quantities requited.

The bill of material often contains a list ofstandard parts, known as a parts list or schedule.Figure 1-4 shows a bill of material for an electricalplan.

Application Block

The application block on a blueprint of a part orassembly (fig. 1-5) identifies directly or by referencethe larger unit that contains the part or assembly onthe drawing. The NEXT ASSY (next assembly)column will contain the drawing number or model

Figure 1-5.Application block.

Figure 1-4.Bill of material.

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number of the next larger assembly of which thesmaller unit or assembly is a part. The USED ONcolumn shows the model number or equivalentdesignation of the assembled units part.

FINISH MARKS

Finish marks (PP ) used on machine drawings showsurfaces to be finished by machining (fig. 1-6).Machining provides a better surface appearance and abetter fit with closely mated parts. Machined finishesare NOT the same as finishes of paint, enamel, grease,chromium plating, and similar coatings.

NOTES AND SPECIFICATIONS

Blueprints show all of the information about anobject or part graphically. However, supervisors,contractors, manufacturers, and craftsmen need moreinformation that is not adaptable to the graphic formof presentation. Such information is shown on thedrawings as notes or as a set of specifications attachedto the drawings.

NOTES are placed on drawings to give additionalinformation to clarify the object on the blueprint (fig.1-2). Leader lines show the precise part notated.

A SPECIFICATION is a statement or documentcontaining a description such as the terms of a contractor details of an object or objects not shown on a blue

print or drawing (fig. 1-2). Specifications describeitems so they can be manufactured, assembled, andmaintained according to their performance require-ments. They furnish enough information to show thatthe item conforms to the description and that it can bemade without the need for research, development,design engineering, or other help from the preparingorganization.

Federal specifications cover the characteristics ofmaterial and supplies used jointly by the Navy andother government departments.

LEGENDS AND SYMBOLS

A legend, if used, is placed in the upper rightcorner of a blueprint below the revision block. Thelegend explains or defines a symbol or special markplaced on the blueprint. Figure 1-2 shows a legend foran electrical plan.

THE MEANING OF LINESTo read blueprints, you must understand the use

of lines. The alphabet of lines is the common languageof the technician and the engineer. In drawing anobject, a draftsman arranges the different views in acertain way, and then uses different types of lines toconvey information. Figure 1-6 shows the use of stan-dard lines in a simple drawing. Line characteristics

Figure 1-6.Use of standard lines.

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such as width, breaks in the line, and zigzags havemeaning, as shown in figure 1-7.

SHIPBOARD BLUEPRINTS

Blueprints are usually called plans. Somecommon types used in the construction, operation,and maintenance of Navy ships are described in thefollowing paragraphs.

PRELIMINARY PLANS are submitted with bidsor other plans before a contract is awarded.

CONTRACT PLANS illustrate mandatory designfeatures of the ship.

CONTRACT GUIDANCE PLANS illustratedesign features of the ship subject to development.

STANDARD PLANS illustrate arrangement ordetails of equipment, systems, or parts where specificrequirements are mandatory.

TYPE PLANS illustrate the general arrangementof equipment, systems, or parts that do not requirestrict compliance to details as long as the work getsthe required results.

WORKING PLANS are those the contractor usesto construct the ship.

CORRECTED PLANS are those that have beencorrected to illustrate the final ship and systemarrangement, fabrication, and installation.

Figure 1-7.Line characteristics and conventions for MIL-STD drawings.

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ONBOARD PLANS are those considerednecessary as reference materials in the operation of aship. A shipbuilder furnishes a completed Navy shipwith copies of all plans needed to operate and maintainthe ship (onboard plans), and a ships plan index (SPI).The SPI lists all plans that apply to the ship exceptthose for certain miscellaneous items covered bystandard or type plans. Onboard plans include onlythose plans NAVSHIPS or the supervisor of shipbuilding consider necessary for shipboard reference.The SPI is NOT a check list for the sole purpose ofgetting a complete set of all plans.

When there is a need for other plans or additionalcopies of onboard plans, you should get them fromyour ships home yard or the concerned systemcommand. Chapter 9001 of the Naval Ships

Technical Manual (NSTM) contains a guide for theselection of onboard plans.

BLUEPRINT NUMBERING PLANIn the current system, a complete plan number has

five parts: (1) size, (2) federal supply codeidentification number, (3 and 4) a system commandnumber in two parts, and (5) a revision letter. Thefollowing list explains each part.

1. The letter under the SIZE block in figure 1-1,view A, shows the size of the blueprint according to atable of format sizes in MIL-STD-100.

2. The federal supply code identification numbershows the design activity. Figure 1-1, view A, shows anexample under the block titled CODE IDENT NO

Figure 1-7.Line characteristics and conventions for MIL-SDT drawingsContinued.

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where the number 80064 identifies NAVSHIPS. In viewB, the number 80091 identifies the Naval FacilitiesEngineering Command.

3. The first part of the system command number isa three-digit group number. It is assigned from theConsolidated Index of Drawings, Materials, andServices Related to Construction and Conversion,NAVSHIPS 0902-002-2000. This number identifies theequipment or system, and sometimes the type of plan.In figure 1-1, view A, the number 800 under theNAVSHIP SYSTEM COMMAND NO. blockidentifies the plan as a contract plan.

4. The second part of the system command numberis the serial or file number assigned by the supervisorof shipbuilding. Figure 1-1, view A, shows the number2647537 as an example under the NAVSHIP SYSTEMCOMMAND NO. block.

5. The revision letter was explained earlier in thechapter. It is shown under the REV block as A in figure1-1, view A.

Figure 1-8, view B, shows the shipboard plannumbering system that was in use before the adoptionof the current system (view A). They two systems aresimilar with the major differences in the group numbersin the second block. We will explain the purpose of eachblock in the following paragraphs so you can comparethe numbers with those used in the current system.

The first block contains the ship identificationnumber. The examples in views A and B are DLG 16and DD 880. Both refer to the lowest numbered shipto which the plan applies.

The second block contains the group number. Inview A, it is a three-digit number 303 taken fromNAVSHIPS 0902-002-2000 and it identifies a lightingsystem plan. View B shows the group number system

Figure 1-8.Shipboard plan numbers.

in use before adoption of the three-digit system. Thatsystem used S group numbers that identify theequipment or system concerned. The example numberS3801 identifies a ventilating system. To use thisnumber, relate it to the proper chapter of an NSTM.Replace the S with the 9 of an NSTM chapter numberand drop the last digit in the number. For example, thenumber S3801 would produce the number 9380, orchapter 9380 of the NSTM titled Ventilation andHeating.

Blocks 3, 4, and 5 use the same information in theold and new systems. Block 3 shows the size of theplan, block 4 shows the system or file number, andblock 5 shows the version of the plan.

FILING AND HANDLING BLUEPRINTSOn most ships, engineering logroom personnel

file and maintain plans. Tenders and repair ships maykeep plan files in the technical library or the microfilmlibrary. They are filed in cabinets in numericalsequence according to the three-digit or S groupnumber and the file number. When a plan is revised,the old one is removed and destroyed. The current planis filed in its place.

The method of folding prints depends upon thetype and size of the filing cabinet and the location ofthe identifying marks on the prints. It is best to placeidentifying marks at the top of prints when you filethem vertically (upright), and at the bottom rightcorner when you file them flat. In some casesconstruction prints are stored in rolls.

Blueprints are valuable permanent records. How-ever, if you expect to keep them as permanent records,you must handle them with care. Here are a few simplerules that will help.

Keep them out of strong sunlight; they fade.

Dont allow them to become wet or smudgedwith oil or grease. Those substances seldom dry outcompletely and the prints can become unreadable.

Dont make pencil or crayon notations on a printwithout proper authority. If you are instructed to marka print, use a proper colored pencil and make themarkings a permanent part of the print. Yellow is a goodcolor to use on a print with a blue background(blueprint).

Keep prints stowed in their proper place. Youmay receive some that are not properly folded and youmust refold them correctly.

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CHAPTER 2

TECHNICAL SKETCHING

When you have read and understood this chapter,you should be able to answer the following learningobjectives:

Describe the instruments used in technicalsketching.

Describe the types of lines used in technicalsketching.

Explain basic computer-aided drafting (CAD).Explain computer numerical control (CNC)design techniques used in machining.

The ability to make quick, accurate sketches is avaluable advantage that helps you convey technicalinformation or ideas to others. A sketch may be of anobject, an idea of something you are thinking about,or a combination of both. Most of us think of a sketchas a freehand drawing, which is not always the case.You may sketch on graph paper to take advantage ofthe lined squares, or you may sketch on plain paperwith or without the help of drawing instruments.

There is no MIL-STD for technical sketching.You may draw pictorial sketches that look like theobject, or you may make an orthographic sketchshowing different views, which we will cover infollowing chapters.

In this chapter, we will discuss the basics offreehand sketching and lettering, drafting, andcomputer aided drafting (CAD). We will also explainhow CAD works with the newer computer numericalcontrol (CNC) systems used in machining.

SKETCHING INSTRUMENTSFreehand sketching requires few tools. If you have

a pencil and a scrap piece of paper handy, you areready to begin. However, technical sketching usuallycalls for instruments that are a little more specialized,and we will discuss some of the more common onesin the following paragraphs.

PENCILS AND LEADS

There are two types of pencils (fig. 2-1), those withconventional wood bonded cases known as wooden

pencils and those with metal or plastic cases known asmechanical pencils. With the mechanical pencil, thelead is ejected to the desired length of projection fromthe clamping chuck.

There are a number of different drawing media andtypes of reproduction and they require different kindsof pencil leads. Pencil manufacturers market three typesthat are used to prepare engineering drawings; graphite,plastic, and plastic-graphite.

Graphite lead is the conventional type we have usedfor years. It is made of graphite, clay, and resin and it isavailable in a variety of grades or hardness. The hardergrades are 9H, 8H, 7H and 6H. The medium grades are5H, 4H, 3H, and 2H. The medium soft grades are H andF. The soft grades are HB, B, and 2B; and the very softgrades are 6B, 5B, 4B, and 3B. The latter grade is notrecommended for drafting. The selection of the gradeof lead is important. A harder lead might penetrate thedrawing, while a softer lead may smear.

Plastic and graphite-plastic leads were developedas a result of the introduction of film as a drawingmedium, and they should be used only on film. Plasticlead has good microform reproduction characteristics,but it is seldom used since plastic-graphite lead wasdeveloped. A limited number of grades are available inthese leads, and they do not correspond to the gradesused for graphite lead.

Plastic-graphite lead erases well, does not smearreadily, and produces a good opaque line suitable for

Figure 2-1.Types of pencils.

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Figure 2-2Types of pens. Figure 2-3.Protractor.

Figure 2-4.The triangles

2-2

microform reproduction. There are two types: firedand extruded. They are similar in material content toplastic fired lead, but they are produced differently.The main drawback with this type of lead is that it doesnot hold a point well.

PENS

Two types of pens are used to produce ink lines:the ruling pen with adjustable blade and theneedle-in-tube type of pen (fig. 2-2). We include theruling pen here only for information; it has beenalmost totally replaced by the needle-in-tube type.

The second type and the one in common use todayis a technical fountain pen, or needle-in-tube type ofpen. It is suitable for drawing both lines and letters.

Figure 2-5Adjustable triangle.

The draftsman uses different interchangeable needlepoints to produce different line widths. Several typesof these pens now offer compass attachments thatallow them to be clamped to, or inserted on, a standardcompass leg.

DRAWING AIDS

Some of the most common drawing aids areprotractors, triangles, and French curves. A protractor(fig. 2-3), is used to measure or lay out angles otherthan those laid out with common triangles. Thecommon triangles shown in figure 2-4 may be used tomeasure or lay out the angles they represent, or theymay be used in combination to form angles inmultiples of 15. However, you may lay out any anglewith an adjustable triangle (fig. 2-5), which replacesthe protractor and common triangles.

The French curve (fig. 2-6) is usually used to drawirregular curves with unlike circular areas where thecurvature is not constant.

TYPES OF LINESThe lines used for engineering drawings must be

clear and dense to ensure good reproduction. Whenmaking additions or revisions to existing drawings, besure the line widths and density match the originalwork. Figure 2-7 shows the common types of straight

Figure 2-6.French (irregular) curves.

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Figure 2-7.Types of lines.

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Figure 2-7.Types of linesContinued.

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lines we will explain in the following paragraphs. Inaddition, we will explain the use of circles and curvedlines at the end of this section.

VISIBLE LINES represent visible edges orcontours of objects. Draw visible lines so that theviews they outline stand out clearly on the drawingwith a definite contrast between these lines andsecondary lines.

HIDDEN LINES consist of short, evenly-spaceddashes and are used to show the hidden features of anobject (fig. 2-8). You may vary the lengths of thedashes slightly in relation to the size of the drawing.Always begin and end hidden lines with a dash, incontrast with the visible lines from which they start,except when a dash would form a continuation of avisible line. Join dashes at comers, and start arcs withdashes at tangent points. Omit hidden lines when theyare not required for the clarity of the drawing.

Although features located behind transparentmaterials may be visible, you should treat them asconcealed features and show them with hidden lines.

CENTER LINES consist of alternating long andshort dashes (fig. 2-9). Use them to represent the axisof symmetrical parts and features, bolt circles, andpaths of motion. You may vary the long dashes of thecenter lines in length, depending upon the size of thedrawing. Start and end center lines with long dashesand do not let them intersect at the spaces betweendashes. Extend them uniformly and distinctly a shortdistance beyond the object or feature of the drawingunless a longer extension line is required for

Figure 2-8.Hidden-line technique.

Figure 2-9.Center-line technique.

dimensioning or for some other purpose. Do notterminate them at other lines of the drawing, norextend them through the space between views. Veryshort center lines may be unbroken if there is noconfusion with other lines.

SYMMETRY LINES are center lines used as axesof symmetry for partial views. To identify the line ofsymmetry, draw two thick, short parallel lines at rightangles to the center line. Use symmetry lines torepresent partially drawn views and partial sections ofsymmetrical parts. You may extend symmetrical viewvisible and hidden lines past the symmetrical line if itwill improve clarity.

EXTENSION and DIMENSION LINES show thedimensions of a drawing. We will discuss them laterin this chapter.

LEADER LINES show the part of a drawing towhich a note refers.

BREAK LINES shorten the view of long uniformsections or when you need only a partial view. Youmay use these lines on both detail and assemblydrawings. Use the straight, thin line with freehandzigzags for long breaks, the thick freehand line forshort breaks, and the jagged line for wood parts.

You may use the special breaks shown in figure2-10 for cylindrical and tubular parts and when an endview is not shown; otherwise, use the thick break line.

CUTTING PLANE LINES show the location ofcutting planes for sectional views.

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Figure 2-10.Conventional break lines.

SECTION LINES show surface in the sectionview imagined to be cut along the cutting plane.

VIEWING-PLANE LINES locate the viewingposition for removed partial views.

PHANTOM LINES consist of long dashesseparated by pairs of short dashes (fig. 2-11). The longdashes may vary in length, depending on the size ofthe drawing. Phantom lines show alternate positionsof related parts, adjacent positions of related parts, and

Figure 2-11.Phantom-line application.

repeated detail. They also may show features such asbosses and lugs to delineate machining stock andblanking developments, piece parts in jigs andfixtures, and mold lines on drawings or formed metalparts. Phantom lines always start and end with longdashes.

STITCH LINES show a sewing and stitchingprocess. Two forms of stitch lines are approved forgeneral use. The first is made of short thin dashes andspaces of equal lengths of approximately 0.016, andthe second is made of dots spaced 0.12 inch apart.

CHAIN LINES consist of thick, alternating longand short dashes. These lines show that a surface orsurface zone is to receive additional treatment orconsiderations within limits specified on a drawing.

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An ELLIPSE is a plane curve generated by a pointmoving so that the sum of the distance from any pointon the curve to two fixed points, called foci, is aconstant (fig. 2-12). Ellipses represent holes onoblique and inclined surfaces.

CIRCLES on drawings most often represent holesor a circular part of an object.

An IRREGULAR CURVE is an unlike circulararc where the radius of curvature is not constant. Thiscurve is usually made with a French curve (fig. 2-6).

An OGEE, or reverse curve, connects two parallellines or planes of position (fig. 2-13).

BASIC COMPUTER AIDED DRAFTING(CAD)

The process of preparing engineering drawings ona computer is known as computer-aided drafting(CAD), and it is the most significant development tooccur recently in this field. It has revolutionized theway we prepare drawings.

The drafting part of a project is often a bottleneckbecause it takes so much time. Drafters spendapproximately two-thirds of their time laying lead.

Figure 2-12.Example of an ellipse.

Figure 2-13.A reverse (ogee) curve connecting two parallelplanes.

But on CAD, you can make design changes faster,resulting in a quicker turn-around time.

CAD also can relieve you from many tediouschores such as redrawing. Once you have made adrawing you can store it on a disk. You may then callit up at any time and change it quickly and easily.

It may not be practical to handle all of the draftingworkload on a CAD system. While you can do mostdesign and drafting work more quickly on CAD, youstill need to use traditional methods for others. Forexample, you can design certain electronics andconstruction projects more quickly on a drafting table.

A CAD system by itself cannot create; it is onlyan additional and more efficient tool. You must usethe system to make the drawing; therefore, you musthave a good background in design and drafting.

In manual drawing, you must have the skill todraw lines and letters and use equipment such asdrafting tables and machines, and drawing aids suchas compasses, protractors, triangles, parallel edges,scales, and templates. In CAD, however, you dontneed those items. A cathode-ray tube, a centralprocessing unit, a digitizer, and a plotter replace them.Figure 2-14 shows some of these items at a computerwork station. Well explain each of them later in thissection.

GENERATING DRAWINGS ON CAD

A CAD computer contains a drafting program thatis a set of detailed instructions for the computer. Whenyou bring up the program, the screen displays eachfunction or instruction you must follow to make adrawing.

The CAD programs available to you contain all ofthe symbols used in mechanical, electrical, orarchitectural drawing. You will use the keyboardand/or mouse to call up the drafting symbols you needas you need them. Examples are characters, gridpatterns, and types of lines. When you get the symbolsyou want on the screen, you will order the computerto size, rotate, enlarge, or reduce them, and positionthem on the screen to produce the image you want.You probably will then order the computer to print thefinal product and store it for later use.

The computer also serves as a filing system for anydrawing symbols or completed drawings stored in itsmemory or on disks. You can call up this informationany time and copy it or revise it to produce a differentsymbol or drawing.

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Figure 2-14.Computer work station.

In the following paragraphs, we will discuss theother parts of a CAD system; the digitizer, plotter, andprinter.

The Digitizer

The digitizer tablet is used in conjunction with aCAD program; it allows the draftsman to change fromcommand to command with ease. As an example, you

can move from the line draw function to an arcfunction without using the function keys or menu barto change modes of operation. Figure 2-15 illustratesa typical digitizer tablet.

The Plotter

A plotter (fig. 2-16) is used mainly to transfer animage or drawing from the computer screen to some

Figure 2-15.Basic digitizer tablet. Figure 2-16.Typical plotter.

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form of drawing media. When you have finishedproducing the drawing on CAD, you will order thecomputer to send the information to the plotter, whichwill then reproduce the drawing from the computerscreen. A line-type digital plotter is an electro-mechanical graphics output device capable of two-dimensional movement between a pen and drawingmedia. Because of the digital movement, a plotter isconsidered a vector device.

You will usually use ink pens in the plotter toproduce a permanent copy of a drawing. Somecommon types are wet ink, felt tip, or liquid ball, andthey may be single or multiple colors. These pens willdraw on various types of media such as vellum andMylar. The drawings are high quality, uniform,precise, and expensive. There are faster, lower qualityoutput devices such as the printers discussed in thenext section, but most CAD drawings are produced ona plotter.

The Printer

A printer is a computer output device thatduplicates the screen display quickly andconveniently. Speed is the primary advantage; it ismuch faster than plotting. You can copy complexgraphic screen displays that include any combinationof graphic and nongraphic (text and characters)symbols. The copy, however, does not approach thelevel of quality produced by the pen plotter. Therefore,it is used primarily to check prints rather than to makea final copy. It is, for example, very useful for a quickpreview at various intermediate steps of a designproject.

The two types of printers in common use are dotmatrix (fig. 2-17) and laser (fig. 2-18). The laserprinter offers the better quality and is generally moreexpensive.

COMPUTER-AIDEDDESIGN/COMPUTER-AIDED

MANUFACTURING

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You read earlier in this chapter how we usecomputer technology to make blueprints. Now youlllearn how a machinist uses computer graphics to layout the geometry of a part, and how a computer on themachine uses the design to guide the machine as itmakes the part. But first we will give you a briefoverview of numerical control (NC) in the field ofmachining.

Figure 2-17.Dot matrix printer.

Figure 2-18.Laser jet printer.

NC is the process by which machines arecontrolled by input media to produce machined parts.The most common input media used in the past weremagnetic tape, punched cards, and punched tape.Today, most of the new machines, including all ofthose at Navy intermediate maintenance activities, arecontrolled by computers and known as computernumerical control (CNC) systems. Figure 2-19 showsa CNC programming station where a machinistprograms a machine to do a given job.

NC machines have many advantages. The greatestis the unerring and rapid positioning movements thatare possible. An NC machine does not stop at the endof a cut to plan its next move. It does not get tired andit is capable of uninterrupted machining, error free,hour after hour. In the past, NC machines were usedfor mass production because small orders were toocostly. But CNC allows a qualified machinist toprogram and produce a single part economically.

Figure 2-19.CNC programming station.

In CNC, the machinist begins with a blueprint, otherdrawing, or sample of the part to be made. Then he orshe uses a keyboard, mouse, digitizer, and/or light pento define the geometry of the part to the computer. Theimage appears on the computer screen where the ma-chinist edits and proofs the design. When satisfied, themachinist instructs the computer to analyze the geome-try of the part and calculate the tool paths that will berequired to machine the part. Each tool path is translatedinto a detailed sequence of the machine axes movementcommands the machine needs to produce the part.

The computer-generated instructions can bestored in a central computers memory, or on a disk,for direct transfer to one or more CNC machine toolsthat will make the parts. This is known as directnumerical control (DNC). Figure 2-20 shows a Figure 2-20.Direct numerical control station.

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Figure 2-21.Direct numerical controller.

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diagram of a controller station, and figure 2-21 shows the tool path into codes that the computer on thea controller. machine can understand.

The system that makes all this possible is known ascomputer-aided design/computer-aided manufacturing(CAD/CAM). There are several CAD/CAM softwareprograms and they are constantly being upgraded andmade more user friendly.

To state it simply, CAD is used to draw the partand to define the tool path, and CAM is used to convert

We want to emphasize that this is a brief overviewof CNC. It is a complicated subject and many bookshave been written about it. Before you can work withCNC, you will need both formal and on-the-jobtraining. This training will become more available asthe Navy expands its use of CNC.

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CHAPTER 3

PROJECTIONS AND VIEWS

When you have read and understood this chapter,you should be able to answer the following learningobjectives:

Describe the types of projections.Describe the types of views.

In learning to read blueprints you must developthe ability to visualize the object to be made from theblueprint (fig. 3-1). You cannot read a blueprint all atonce any more than you can read an entire page of printall at once. When you look at a multiview drawing,first survey all of the views, then select one view at atime for more careful study. Look at adjacent views todetermine what each line represents.

Each line in a view represents a change in thedirection of a surface, but you must look at anotherview to determine what the change is. A circle on oneview may mean either a hole or a protruding boss(surface) as shown in the top view in figure 3-2. Whenyou look at the top view you see two circles, and youmust study the other view to understand what eachrepresents. A glance at the front view shows that thesmaller circle represents a hole (shown in dashedlines), while the larger circle represents a protrudingboss. In the same way, you must look at the top viewto see the shape of the hole and the protruding boss.

Figure 3-1.Visualizing a blueprint.

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You can see from this example that you cannotread a blueprint by looking at a single view, if morethan one view is shown. Sometimes two views maynot be enough to describe an object; and when thereare three views, you must view all three to be sure youread the shape correctly.

PROJECTIONSIn blueprint reading, a view of an object is known

technically as a projection. Projection is done, intheory, by extending lines of sight called projectorsfrom the eye of the observer through lines and pointson the object to the plane of projection. This procedurewill always result in the type of projection shown in

Figure 3-2.Reading views.

fig. 3-3. It is called central projection because the linesof sight, or projectors, meet at a central point; the eyeof the observer.

You can see that the projected view of the objectvaries considerably in size, according to the relativepositions of the objects and the plane of projection. Itwill also vary with the distance between the observerand the object, and between the observer and the planeof projection. For these reasons, central projection isseldom used in technical drawings.

If the observer were located a distance away fromthe object and its plane of projection, the projectorswould not meet at a point, but would be parallel to eachother. For reasons of convenience, this parallelprojection is assumed for most technical drawings andis shown in figure 3-4. You can see that, if theprojectors are perpendicular to the plane of projection,a parallel projection of an object has the samedimensions as the object. This is true regardless of therelative positions of the object and the plane ofprojection, and regardless of the distance from theobserver.

ORTHOGRAPHIC AND OBLIQUEPROJECTION

An ORTHOGRAPHIC projection is a parallelprojection in which the projectors are perpendicular tothe plane of projection as in figure 3-4. An OBLIQUEprojection is one in which the projectors are other thanperpendicular to the plane of projection. Figure 3-5shows the same object in both orthographic andoblique projections. The block is placed so that its

Figure 3-3.Central projection.

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Figure 3-4.Parallel projections.

Figure 3-5.Oblique and orthographic projections.

front surface (the surface toward the plane ofprojection) is parallel to the plane of projection. Youcan see that the orthographic (perpendicular)projection shows only this surface of the block, whichincludes only two dimensions: length and width. Theoblique projection, on the other hand, shows the frontsurface and the top surface, which includes threedimensions: length, width, and height. Therefore, anoblique projection is one way to show all threedimensions of an object in a single view. Axonometricprojection is another and we will discuss it in the nextparagraphs.

ISOMETRIC PROJECTION

Isometric projection is the most frequently usedtype of axonometric projection, which is a methodused to show an object in all three dimensions in asingle view. Axonometric projection is a form oforthographic projection in which the projectors arealways perpendicular to the plane of projection.However, the object itself, rather than the projectors,are at an angle to the plane of projection.

Figure 3-6 shows a cube projected by isometricprojection. The cube is angled so that all of its surfacesmake the same angle with the plane of projection. As aresult, the length of each of the edges shown in theprojection is somewhat shorter than the actual length ofthe edge on the object itself. This reduction is calledforeshortening. Since all of the surfaces make the anglewith the plane of projection, the edges foreshorten inthe same ratio. Therefore, one scale can be used for theentire layout; hence, the term isometric which literallymeans the same scale.

VIEWSThe following pages will help you understand the

types of views commonly used in blueprints.

MULTIVIEW DRAWINGS

The complexity of the shape of a drawing governsthe number of views needed to project the drawing.Complex drawings normally have six views: bothends, front, top, rear, and bottom. However, mostdrawings are less complex and are shown in threeviews. We will explain both in the followingparagraphs.

Figure 3-7 shows an object placed in a transparentbox hinged at the edges. With the outlines scribed oneach surface and the box opened and laid flat as shownin views A and C, the result is a six-view orthographic

Figure 3-7.Third-angle orthographic projection.

Figure 3-6.Isometric projection.

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projection. The rear plane is hinged to the right sideplane, but it could hinge to either of the side planes orto the top or bottom plane. View B shows that theprojections on the sides of the box are the views youwill see by looking straight at the object through eachside. Most drawings will be shown in three views, butoccasionally you will see two-view drawings,particularly those of cylindrical objects.

A three-view orthographic projection drawingshows the front, top, and right sides of an object. Referto figure 3-7, view C, and note the position of each ofthe six sides. If you eliminate the rear, bottom, and leftsides, the drawing becomes a conventional 3-viewdrawing showing only the front, top, and right sides.

Study the arrangement of the three-view drawingin figure 3-8. The views are always in the positionsshown. The front view is always the starting point andthe other two views are projected from it. You may useany view as your front view as long as you place it inthe lower-left position in the three-view. This frontview was selected because it shows the mostcharacteristic feature of the object, the notch.

Figure 3-9.Pull off the views.

The right side or end view is always projected tothe right of the front view. Note that all horizontaloutlines of the front view are extended horizontally tomake up the side view. The top view is alwaysprojected directly above the front view and the verticaloutlines of the front view are extended vertically to thetop view.

After you study each view of the object, you cansee it as it is shown in the center of figure 3-9. Toclarify the three-view drawing further, think of theobject as immovable (fig. 3-10), and visualize yourselfmoving around it. This will help you relate theblueprint views to the physical appearance of theobject.

Figure 3-8.A three-view orthographic projection.

Figure 3-10.Compare the orthographic views with themodel.

Now study the three-view drawing shown infigure 3-11. It is similar to that shown in figure 3-8with one exception; the object in figure 3-11 has a holedrilled in its notched portion. The hole is visible in thetop view, but not in the front and side views.Therefore, hidden (dotted) lines are used in the frontand side views to show the exact location of the wallsof the hole.

The three-view drawing shown in figure 3-11introduces two symbols that are not shown in figure3-8 but are described in chapter 2. They are a hiddenline that shows lines you normally cant see on theobject, and a center line that gives the location of theexact center of the drilled hole. The shape and size ofthe object are the same.

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Auxiliary Views

Figure 3-11.A three-view drawing.

PERSPECTIVE DRAWINGSA perspective drawing is the most used method of

presentation used in technical illustrations in thecommercial and architectural fields. The drawnobjects appear proportionately smaller with distance,as they do when you look at the real object (fig. 3-12).It is difficult to draw, and since the drawings are drawnin diminishing proportion to the edges represented,they cannot be used to manufacture an object. Otherviews are used to make objects and we will discusthem in the following paragraphs.

SPECIAL VIEWSIn many complex objects it is often difficult to

show true size and shapes orthographically.Therefore, the draftsmen must use other views to giveengineers and craftsmen a clear picture of the objectto be constructed. Among these are a number ofspecial views, some of which we will discuss in thefollowing paragraphs.

Auxiliary views are often necessary to show thetrue shape and length of inclined surfaces, or otherfeatures that are not parallel to the principal planes ofprojection.

Look directly at the front view of figure 3-13.Notice the inclined surface. Now look at the right sideand top views. The inclined surface appearsforeshortened, not its true shape or size. In this case,the draftsman will use an auxiliary view to show thetrue shape and size of the inclined face of the object.It is drawn by looking perpendicular to the inclinedsurface. Figure 3-14 shows the principle of theauxiliary view.

Look back to figure 3-10, which shows an immov-able object being viewed from the front, top, and side.Find the three orthographic views, and compare them

Figure 3-13.Auxiliary view arrangement.

Figure 3-12.The perspective. Figure 3-14.Auxiliary projection principle.

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with figure 3-15 together with the other information. Itshould clearly explain the reading of the auxiliary view.Figure 3-16 shows a side by side comparison of ortho-graphic and auxiliary views. View A shows a fore-shortened orthographic view of an inclined or slantedsurface whose true size and shape are unclear. View Buses an auxiliary projection to show the true size andshape.

The projection of the auxiliary view is made by theobserver moving around an immovable object, and theviews are projected perpendicular to the lines of sight.Remember, the object has not been moved; only theposition of the viewer has changed.

Section Views

Section views give a clearer view of the interior orhidden features of an object that you normally cannotsee clearly in other views. A section view is made byvisually cutting away a part of an object to show theshape and construction at the cutting plane.

Figure 3-15.Viewing an inclined surface, auxiliary view.

Figure 3-16.Comparison of orthographic and auxiliaryprojections.

Notice the cutting plane line AA in the front viewshown in figure 3-17, view A. It shows where theimaginary cut has been made. In view B, the isometricview helps you visualize the cutting plane. The arrowspoint in the direction in which you are to look at thesectional view.

View C is another front view showing how theobject would look if it were cut in half.

In view D, the orthographic section view of sectionA-A is placed on the drawing instead of the confusingfront view in view A. Notice how much easier it is toread and understand.

When sectional views are drawn, the part that iscut by the cutting plane is marked with diagonal (orcrosshatched), parallel section lines. When two or moreparts are shown in one view, each part is sectioned orcrosshatched with a different slant. Section views arenecessary for a clear understanding of complicatedparts. On simple drawings, a section view may serve thepurpose of additional views.

Figure 3-17.Action of a cutting plane.

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Section A-A in view D is known as a full sectionbecause the object is cut completely through.

OFFSET SECTION.In this type of section, thecutting plane changes direction backward and forward(zig-zag) to pass through features that are important toshow. The offset cutting plane in figure 3-18 ispositioned so that the hole on the right side will beshown in section. The sectional view is the front view,and the top view shows the offset cutting plane line.

HALF SECTION.This type of section isshown in figure 3-19. It is used when an object issymmetrical in both outside and inside details.One-half of the object is sectioned; the other half isshown as a standard view.

The object shown in figure 3-19 is cylindrical andcut into two equal parts. Those parts are then dividedequally to give you four quarters. Now remove a quar-ter. This is what the cutting plane has done in thepictorial view; a quarter of the cylinder has been re-

Figure 3-18.Offset section.

Figure 3-19.Half section.

moved so you can look inside. If the cutting plane hadextended along the diameter of the cylinder, you wouldhave been looking at a full section. The cutting plane inthis drawing extends the distance of the radius, or onlyhalf the distance of a full section, and is called a halfsection.

The arrow has been inserted to show your line ofsight. What you see from that point is drawn as a halfsection in the orthographic view. The width of theorthographic view represents the diameter of thecircle. One radius is shown as a half section, the otheras an external view.

REVOLVED SECTION.This type of sectionis used to eliminate the need to draw extra views ofrolled shapes, ribs, and similar forms. It is really adrawing within a drawing, and it clearly describes theobjects shape at a certain cross section. In figure 3-20,the draftsman has revolved the section view of the ribso you can look at it head on. Because of this revolvingfeature, this kind of section is called a revolvedsection.

REMOVED SECTION.This type of section isused to illustrate particular parts of an object. It isdrawn like the revolved section, except it is placed atone side to bring out important details (fig. 3-21). It is

Figure 3-20.Revolved section.

Figure 3-21.Removed section.

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often drawn to a larger scale than the view of the objectfrom which it is removed.

BROKEN-OUT SECTION.The inner struc-ture of a small area may be shown by peeling back orremoving the outside surface. The inside of a

Figure 3-22.Broken-out section through a counterbored Exploded Viewhole.

Figure 3-23.Aligned section.

counterbored hole is better illustrated in figure 3-22because of the broken-out section, which makes itpossible for you to look inside.

ALIGNED SECTION.Figure 3-23 shows analigned section. Look at the cutting-plane line AA onthe front view of the handwheel. When a truesectional view might be misleading, parts such as ribsor spokes are drawn as if they are rotated into or outof the cutting plane. Notice that the spokes in sectionA-A are not sectioned. If they were, the firstimpression might be that the wheel had a solid webrather than spokes.

This is another type of view that is helpful andeasy to read. The exploded view (fig. 3-24) is used toshow the relative location of parts, and it isparticularly helpful when you must assemble complexobjects. Notice how parts are spaced out in line toshow clearly each parts relationship to the otherparts.

DETAIL DRAWINGS

A detail drawing is a print that shows a singlecomponent or part. It includes a complete and exactdescription of the parts shape and dimensions, andhow it is made. A complete detail drawing will showin a direct and simple manner the shape, exact size,type of material, finish for each part, tolerance,necessary shop operations, number of parts required,and so forth. A detail drawing is not the same as a

Figure 3-24.An exploded view.

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Figure 3-25.Detailed drawing of a clevis.

detail view. A detail view shows part of a drawing inthe same plane and in the same arrangement, but ingreater detail to a larger scale than in the principalview.

Figure 3-25 shows a relatively simple detaildrawing of a clevis. Study the figure closely and applythe principles for reading two-view orthographicdrawings discussed earlier in this chapter. The dimen-sions on the detail drawing in figure 3-25 are conven-tional, except for the four toleranced dimensionsgiven. In the top view, on the right end of the part, isa hole requiring a diameter of 0.3125 +0.0005, butno (minus). This means that the diameter of the holecan be no less than 0.3125, but as large as 0.3130. Inthe bottom view, on the left end of the part, there is adiameter of 0.665 0.001. This means the diametercan be a minimum of 0.664, and a maximum of 0.666.The other two toleranced dimension given are at theleft of the bottom view. Figure 3-26 is an isometricview of the clevis shown in figure 3-25.

Figure 3-26.Isometric drawing of a clevis.

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Figure 3-27 is an isometric drawing of the basepivot shown orthographically in figure 3-28. You maythink the drawing is complicated, but it really is not.It does, however, have more symbols and abbrevia-tions than this book has shown you so far.

Various views and section drawings are oftennecessary in machine drawings because of compli-cated parts or components. It is almost impossible toread the multiple hidden lines necessary to show theobject in a regular orthographic print. For this reasonmachine drawings have one more view that shows theinterior of the object by cutting away a portion of thepart. You can see this procedure in the upper portionof the view on the left of figure 3-28. Figure 3-27.Isometric drawing of a base pivot.

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Figure 3-28.Detail drawing of a base pivot.

CHAPTER 4

MACHINE DRAWING

When you have read and understood this chapter,you should be able to answer the following learningobjectives:

Describe basic machine drawings.

Describe the types of machine threads.Describe gear and helical spring nomenclature.

Explain the use of finish marks on drawings.This chapter discusses the common terms, tools,

and conventions used in the production of machinedrawings.

COMMON TERMS AND SYMBOLSIn learning to read machine drawings, you must first

become familiar with the common terms, symbols, andconventions defined and discussed in the followingparagraphs.GENERAL TERMS

The following paragraphs cover the common termsmost used in all aspects of machine drawings.

TolerancesEngineers realize that absolute accuracy is

impossible, so they figure how much variation ispermissible. This allowance is known as tolerance. Itis stated on a drawing as (plus or minus) a certainamount, either by a fraction or decimal. Limits are themaximum and/or minimum values prescribed for aspecific dimension, while tolerance represents the totalamount by which a specific dimension may vary.Tolerances may be shown on drawings by severaldifferent methods; figure 4-1 shows three examples.The unilateral method (view A) is used when variationfrom the design size is permissible in one direction only.In the bilateral method (view B), the dimension figureshows the plus or minus variation that is acceptable. Inthe limit dimensioning method (view C), the maximumand minimum measurements are both stated

The surfaces being toleranced have geometricalcharacteristics such as roundness, or perpendicularity toanother surface. Figure 4-2 shows typical geometricalcharacteristic symbols. A datum is a surface, line, or

Figure 4-1.Methods of indicating tolerance.

Figure 4-2.Geometric characteristic symbols.

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point from which a geometric position is to bedetermined or from which a distance is to be measured.Any letter of the alphabet except I, O, and Q may beused as a datum identifying symbol. A feature controlsymbol is made of geometric symbols and tolerances.Figure 4-3 shows how a feature control symbol mayinclude datum references.Fillets and Rounds

Fillets are concave metal corner (inside) surfaces.In a cast, a fillet normally increases the strength of ametal corner because a rounded corner cools moreevenly than a sharp corner, thereby reducing thepossibility of a break. Rounds or radii are edges oroutside corners that have been rounded to preventchipping and to avoid sharp cutting edges. Figure 4-4shows fillets and rounds.Slots and Slides

Slots and slides are used to mate two speciallyshaped pieces of material and securely hold themtogether, yet allow them to move or slide. Figure 4-5shows two types: the tee slot, and the dovetail slot. Forexamples, a tee slot arrangement is used on a millingmachine table, and a dovetail is used on the cross slideassembly of an engine lathe.Keys, Keyseats, and Keyways

A key is a small wedge or rectangular piece of metalinserted in a slot or groove between a shaft and a hub toprevent slippage. Figure 4-6 shows three types of keys.

Figure 4-3.Feature control frame indicating a datumreference.

Figure 4-4.Fillets and rounds

Figure 4-5.Slots and slides.

Figure 4-6.Three types of keys.

Figure 4-7 shows a keyseat and keyway. View Ashows a keyseat, which is a slot or groove on the outsideof a part into which the key fits. View B shows akeyway, which is a slot or groove within a cylinder, tube,or pipe. A key fitted into a keyseat will slide into thekeyway and prevent movement of the parts.

SCREW THREADSDraftsmen use different methods to show thread on

drawings. Figures 4-8 through 4-11 show several of

Figure 4-7.A keyseat and keyway.

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Figure 4-8.Simplified method of thread representation.

Figure 4-9.Schematic method of thread representation.

Figure 4-10.Detailed method of thread representation.

FIgure 4-11.Tapered pipe thread representation.

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them. Now look at figure 4-12. The left side shows athread profile in section and the right side shows acommon method of drawing threads. To save time, thedraftsman uses symbols that are not drawn to scale. Thedrawing shows the dimensions of the threaded part butother information may be placed in notes almost anyplace on the drawing but most often in the upper leftcorner. However, in our example the note is directlyabove the drawing and shows the thread designator1/4-20 UNC-2.

The first number of the note, 1/4, is the nominal sizewhich is the outside diameter. The number after the firstdash, 20, means there are 20 threads per inch The lettersUNC identify the thread series as Unified NationalCoarse. The last number, 2, identifies the class of threadand tolerance, commonly called the fit. If it is aleft-hand thread, a dash and the letters LH will followthe class of thread. Threads without the LH areright-hand threads.

Specifications necessary for the manufacture ofscrews include thread diameter, number of threads perinch, thread series, and class of thread The two mostwidely used screw-thread series are (1) Unified or

Figure 4-12.Outside threads.

National Form Threads, which are called NationalCoarse, or NC, and (2) National Fine, or NF threads.The NF threads have more threads per inch of screwlength than the NC.

Classes of threads are distinguished from each otherby the amount of tolerance and/or allowance specified.Classes of thread were formerly known as class of fit, aterm that will probably remain in use for many years.The new term, class of thread, was established by theNational Bureau of Standards in the Screw-ThreadStandards for Federal Services, Handbook H-28.

Figure 4-13 shows the terminology used to describescrew threads. Each of the terms is explained in thefollowing list:

HELIXThe curve formed on any cylinder by astraight line in a plane that is wrapped around thecylinder with a forward progression.

EXTERNAL THREADA thread on the outsideof a member. An example is the thread of a bolt.

INTERNAL THREADA thread on the inside ofa member. An example is the thread inside a nut.

MAJOR DIAMETERThe largest diameter of anexternal or internal thread

AXISThe center line running lengthwise througha screw.

CRESTThe surface of the thread correspondingto the major diameter of an external thread and the minordiameter of an internal thread.

Figure 4-13.Screw thread terminology.

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ROOTThe surface of the thread corresponding to identify the necessary dimensions. Figure 4-14 showsthe minor diameter of an external thread and the major gear nomenclature, and the terms in the figure arediameter of an internal thread explained in the following list:

DEPTHThe distance from the root of a thread tothe crest, measured perpendicularly to the axis.

PITCHThe distance from a point on a screwthread to a corresponding point on the next thread,measured parallel to the axis.

LEADThe distance a screw thread advances onone turn, measured parallel to the axis. On asingle-thread screw the lead and the pitch are identical;on a double-thread screw the lead is twice the pitch; ona triple-thread screw the lead is three times the pitch

GEARS

When gears are drawn on machine drawings, the

PITCH DIAMETER (PD)The diameter of thepitch circle (or line), which equals the number of teethon the gear divided by the diametral pitch

DIAMETRAL PITCH (DP)The number of teethto each inch of the pitch diameter or the number of teethon the gear divided by the pitch diameter. Diametralpitch is usually referred to as simply PITCH.

NUMBER OF TEETH (N)The diametral pitchmultiplied by the diameter of the pitch circle (DP x PD).

ADDENDUM CIRCLE (AC)The circle over thetops of the teeth.

OUTSIDE DIAMETER (OD)The diameter ofdraftsman usually draws only enough gear teeth to the addendum circle.

Figure 4-14.Gear nomenclature.

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CIRCULAR PITCH (CP)The length of the arc ofthe pitch circle between the centers or correspondingpoints of adjacent teeth.

ADDENDUM (A)The height of the tooth abovethe pitch circle or the radial distance between the pitchcircle and the top of the tooth.

DEDENDUM (D)The length of the portion of thetooth from the pitch circle to the base of the tooth.

CHORDAL PITCHThe distance from center tocenter of teeth measured along a straight line or chordof the pitch circle.

ROOT DIAMETER (RD)The diameter of thecircle at the root of the teeth.

CLEARANCE (C)The distance between thebottom of a tooth and the top of a mating tooth.

WHOLE DEPTH (WD)The distance from thetop of the tooth to the bottom, including the clearance.

FACEThe working surface of the tooth over thepitch line.

THICKNESSThe width of the tooth, taken as achord of the pitch circle.

PITCH CIRCLEThe circle having the pitchdiameter.

WORKING DEPTHThe greatest depth to whicha tooth of one gear extends into the tooth space ofanother gear.

RACK TEETHA rack may be compared to a spurgear that has been straightened out. The linear pitch ofthe rack teeth must equal the circular pitch of the matinggear.

HELICAL SPRINGS

There are three classifications of helical springs:compression, extension, and torsion. Drawings seldomshow a true presentation of the helical shape; instead,they usually show springs with straight lines. Figure4-15 shows several methods of spring representationincluding both helical and straight-line drawings. Also,springs are sometimes shown as single-line drawings asin figure 4-16.

FINISH MARKS

The military standards for finish marks are set forthin ANSI 46.1-1962. Many metal surfaces must befinished with machine tools for various reasons. Theacceptable roughness of a surface depends upon how the

Figure 4-15.Representation of commm types of helicalsprings.

Figure 4-16.Single line representation of springs

part will be used. Sometimes only certain surfaces of apart need to be finished while others are not. A modifiedsymbol (check mark) with a number or numbers aboveit is used to show these surfaces and to specify the degreeof finish. The proportions of the surface roughnesssymbol are shown in figure 4-17. On small drawingsthe symbol is proportionately smaller.

The number in the angle of the check mark, in thiscase 02, tells the machinist what degree of finish thesurface should have. This number is theroot-mean-square value of the surface roughness heightin millionths of an inch. In other words, it is ameasurement of the depth of the scratches made by themachining or abrading process.

Wherever possible, the surface roughness symbol isdrawn touching the line representing the surface

Figure 4-17.Proportions for a basic finish symbol.

to

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which it refers. If space is limited, the symbol may beplaced on an extension line on that surface or on the tailof a leader with an arrow touching that surface as shownin figure 4-18.

When a part is to be finished to the same roughnessall over, a note on the drawing will include the directionfinish all over along the finish mark and the propernumber. An example is FINISH ALL OVER32. Whena part is to be finished all over but a few surfaces varyin roughness, the surface roughness symbol number ornumbers are applied to the lines representing thesesurfaces and a note on the drawing will include thesurface roughness symbol for the rest of the surfaces.For example, ALL OVER EXCEPT AS NOTED (fig.4-19).

Figure 4-18.Methods of placing surface roughness symbols.

STANDARDSAmerican industry has adopted a new standard,

Geometrical Dimensioning and Tolerancing, ANSIY14.5M-1982. This standard is used in all blueprintproduction whether the print is drawn by a human handor by computer-aided drawing (CAD) equipment. Itstandardizes the production of prints from the simplisthand-made job on site to single or multiple-run itemsproduced in a machine shop with computer-aidedmanufacturing (CAM) which we explained in chapter2. DOD is now adopting this standard For furtherinformation, refer to ANSI Y14.5M-1982 and toIntroduction to Geometrical Dimensioning andTolerancing, Lowell W. Foster, National Tooling andMachining Association, Fort Washington, MD, 1986.

The following military standards contain most ofthe information on symbols, conventions, tolerances,and abbreviations used in shop or working drawings:

ANSI Y14.5M-1982 Dimensioning and Tolerancing

MIL-STD-9A Screw Thread Conventions andMethods of Specifying

ANSI 46.1

MIL-STD-12,C

Surface Texture

Abbreviations for Use On Drawingsand In Technical-Type Publications

FIgure 4-19.Typical examples of symbol use.

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CHAPTER 5

PIPING SYSTEMS

When you have read and understood this chapter,you should be able to answer the following learningobjectives:

Interpret piping blueprints.

Identify shipboard hydraulic and plumbingblueprints.

PIPING DRAWINGS

Water was at one time the only important fluid thatwas moved from one point to another in pipes. Todayalmost every conceivable fluid is handled in pipesduring its production, processing, transportation, anduse. The age of atomic energy and rocket power hasadded fluids such as liquid metals, oxygen, andnitrogen to the list of more common fluids such as oil,

Figure 5-1.Single-line orthographic pipe drawing.

water, gases, and acids that are being carried in pipingsystems today. Piping is also used as a structuralelement in columns and handrails. For these reasons,drafters and engineers should become familiar withpipe drawings.

Piping drawings show the size and location ofpipes, fittings, and valves. A set of symbols has beendeveloped to identify these features on drawings. Wewill show and explain the symbols later in this chapter.

Two methods of projection used in pipe drawingsare orthographic and isometric (pictorial). Chapter 3has a general description of these methods and thefollowing paragraphs explain their use in pipedrawings.

ORTHOGRAPHIC PIPE DRAWINGS

Single- and double-line orthographic pipedrawings (fig. 5-1 and 5-2) are recommended forshowing single pipes either straight or bent in oneplane only. This method also may be used for morecomplicated piping systems.

ISOMETRIC (PICTORIAL) PIPEDRAWINGS

Pictorial projection is used for all pipes bent inmore than one plane, and for assembly and layoutwork. The finished drawing is easier to understand inthe pictorial format.

Figure 5-2.Double-line orthographic pipe drawing.

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Draftsmen use single-line drawings to show thearrangement of pipes and fittings. Figure 5-3 is asingle-line (isometric) pictorial drawing of figure 5-1.The center line of the pipe is drawn as a thick line towhich the valve symbols are added.

Single-line drawings take less time and show allinformation required to lay out and produce a pipingsystem.

Double-line pipe drawings (fig. 5-4) require moretime to draw and therefore are not recommended forproduction drawings. Figure 5-4 is an example of a

Figure 5-3.Single-line pictorial piping drawing of figure 5-1.

double-line pictorial pipe drawing. They are generallyused for catalogs and similar applications where visualappearance is more important than drawing time.

CROSSINGS

The crossing of pipes without connections isnormally shown without interrupting the linerepresenting the hidden line (fig. 5-5, view A). Butwhen there is a need to show that one pipe must passbehind another, the line representing the pipe farthestfrom the viewer will be shown with a break, orinterruption, where the other pipe passes in front of it,as shown in figure 5-5, view B.

CONNECTIONS

Permanent connections, whether made by weldingor other processes such as gluing or soldering, shouldbe shown on the drawing by a heavy dot (fig. 5-6). Thedraftsman normally will use a general note orspecification to describe the type of connection.

Detachable connections are shown by a singlethick line (figs. 5-6 and 5-7). The specification, ageneral note, or bill of material will list the types ofconnections such as flanges, unions, or couplings andwhether the fittings are flanged or threaded.

Figure 5-4.Double-line pictorial piping drawing.

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Figure 5-5.Crossing of pipes.

Figure 5-6.Pipe connection.

Figure 5-7.Adjoining apparatus.

FITTINGS

If standard symbols for fittings like tees, elbows,crossings, and so forth are not shown on a drawing,they are represented by a continuous line. The circularsymbol for a tee or elbow may be used when it isnecessary to show the piping coming toward ormoving away from the viewer. Figure 5-8, views Aand B, show circular symbols for a connection withand without flanges.

Symbols and Markings

MIL-STD-17B, part I, lists mechanical symbolsused on piping prints other than those foraeronautical, aerospacecraft, and spacecraft, whichare listed in MIL-STD-17B, part II. Figure 5-9 showscommon symbols from MIL-STD-17B, part I. Notethat the symbols may show types of connections

Figure 5-8.Indicating ends of pipe and fittings.

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Figure 5-9.Symbols used in engineering plans and diagrams.

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Figure 5-9.Symbols used in engineering plans and diagramContinued.

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Figure 5-10.Pipe line symbols.

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(screwed, flanged, welded, and so forth) as well asfittings, valves, gauges, and items of equipment.When an item is not covered in the standards, theresponsible activity designs a suitable symbol andexplains it in a note.

Figure 5-10 shows some of the common pipingsymbols used in piping prints. When a print showsmore than one piping system of the same kind,additional letters are added to the symbols todifferentiate between the systems.

MIL-STD-101C established the color code usedto identify piping carrying hazardous fluids. It appliesto all piping installations in naval industrial plants andshore stations where color coding is used. While allvalve wheels on hazardous fluid piping must be colorcoded, the piping itself is optional. The following

colors are painted on valve wheels and pipe linescarrying hazardous fluids:

Yellow Flammable materialsBrown Toxic and poisonous materials

Blue Anesthetics and harmful materialsGreen Oxidizing materialsGray Physically dangerous materialsRed Fire protection materials

Fluid lines in aircraft are marked accordingto MIL-STD-1247C, Markings, Functions, andDesignations of Hoses, Piping, and Tube Lines forAircraft, Missiles, and Space Systems. Figure 5-11lists the types of aircraft fluid lines with the color codeand symbol for each type. Aircraft fluid lines are also

Figure 5-11.Aircraft fluid line color code and symbols.

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marked with an arrow to show direction of flow and uses the standard symbols shown in figure 5-9, andhazard marking, as you will see later in this chapter. that it includes a symbol list. Some small pipingThe following paragraphs contain markings for the diagrams do not include a symbol list; therefore, youfour general classes of hazards, and figure 5-12 shows must be familiar with the standard symbols toexamples of the hazards in each class. interpret these diagrams.

FLAM This marking identifies all materialsordinarily known as flammable or combustible.

TOXIC This marking identifies materials thatare extremely hazardous to life or health.

AAHM This marking identifies anestheticsand harmful materials. These include all materialsthat produce anesthetic vapors. They also includethose that do not normally produce dangerous fumesor vapors, but are hazardous to life and property.

PHDAN This marking identifies a line thatcarries material that is not dangerous in itself, but isasphyxiating in confined areas. These materials aregenerally handled in a dangerous physical state ofpressure or temperature.

SHIPBOARD PIPING PRINTSThere are various types of shipboard piping

systems. Figure 5-13 shows a section of a pipingdiagram for a heavy cruiser. Note that the drawing

Standard symbols are generally not used indrawings of shipboard piping systems found inoperation and maintenance manuals. Each fitting inthose systems may be drawn in detail (pictorially), asshown in figure 5-14, or a block diagram arrangement(fig. 5-15) may be used.

HYDRAULIC PRINTSThe Navy has increased its use of hydraulic sys-

tems, tools, and machines in recent years. Hydraulicsystems are used on aircraft and aboard ship toactivate weapons, navigational equipment, andremote controls of numerous mechanical devices.Shore stations use hydraulically operated main-tenance and repair shop equipment. Hydraulicsystems are also used in construction, automotive, andweight-handling equipment. Basic hydraulicprinciples are discussed in the basic training courseFluid Power, NAVEDTRA 12064.

To help you distinguish one hydraulic line fromanother, the draftsman designates each line according

FLUID

Air (under pressure)Alcohol

Carbon dioxide

FREON

Gaseous oxygen

Liquid nitrogen

LPG (liquid petroleum gas)Nitrogen gas

Oils and greases

JP-5

Trichloroethylen