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Engineering DRG practice- A Refresher Course -

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Engineering DRG practice

Introduction: What is Engineering Drawing? DRG is the language of Engineers. It is the principal means of communication in ENGG. It is the method used to impart ideas, convey information, specify shape, configuration and size. It is an international language and is bound, like any other language, by rules and conventions.

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Engineering DRG practice

Projections DRG standards Sheet sizes Folding Filing

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Engineering DRG practice

Picture planes :

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Engineering DRG practice

Projections: Projection is the representation on a plane surface the image of

an object observed by a viewer. In graphical language shape is described by projections as geometric figures. The image of the object, formed by rays of sight (lines of projection) taken in some particular direction from the object on to a plane form a view in any DRG.

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Engineering DRG practice

Orthographic projection: It is a particular type of projection in which the objects image isprojected onto three mutually perpendicular planes. If the viewing point (eye) is at an infinite distance from the object such that the projection lines are parallel to one another and perpendicular to the picture plane, the projection obtained is called Orthographic projection. It represents the exact shape of a three dimensional object on a two dimensional sheet in two or more views.

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Engineering DRG practice

Orthographic projection: These

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views require good imagination to interpret and visualize

the details of objects This method is universally used in ENGG DRG to represent objects. Orthographic views are required for the manufacture of objects and machine parts. Front view, top view and Side view of an object are the principal Orthographic views. Two types of Orthographic projections are used: - First angle projection - Third angle projection

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Engineering DRG practice

First angle projection :

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Engineering DRG practice

First angle projection :1. 2. 3. 4. 5. Object is kept above the H.P and in front of V.P. (i.e. in the first quadrant). The object is projected on the V.P. and the H.P. The object lies between the observer and the plane of projection. H.P. is then rotated in clockwise direction through 900 such that the V.P. and the H.P. are brought in line with each other. In this projection method, the top view appears below the front view and left side view appears on the right of the front view.

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Engineering DRG practice

Third angle projection :

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Engineering DRG practice

Third angle projection :1. 2. 3. 4. 5. 6. Object is kept behind the V.P. and below the H.P. (i.e. in the third quadrant). The projection plane lies between the observer and the object. The projection planes are assumed to be transparent. The object is projected on the V.P. and the H.P. H.P. is then rotated in clockwise direction through 900 such that the V.P. and the H.P. are brought in line with each other. In this projection method, the top view appears above the front view and left side view appears on the left of the front view.

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Engineering DRG practice

Other types of projections:

Oblique Isometric Perspective

Note: 1. Oblique and Isometric views are often used in the preparation of maintenance manuals and parts lists of ENGG equipment / assemblies. 2. Perspective views are mostly used by artists.

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Engineering DRG practice

Other types of projections: Oblique Projection: It has two axes at right angles to each other.

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The third axis may be at any angle to the horizontal, 300 or 450 are being generally used. The measurement along the third axis are halved.

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Engineering DRG practice

Other types of projections: contdIsometric Projection: It is a special type of pictorial projection showing the three DIM of an object in one view. It conveys the real shape of the object. Isometric projection of any object is the single orthographic projection of the object placed so that all its three axes are equally inclined to the plane of projection. In this position, all the three sides of the object are exposed to the viewer. Isometric scale = 0.815 x True length

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Engineering DRG practice

DRG Standards

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Engineering DRG practice The following are some of the BIS standards relevant to Engineering DRG practice :

These standards are reviewed and revised from time to timeIS:10714 - 1983 General principles of presentation on technical drawings IS:9609 (part1)-1983 Lettering on technical drawings (part1 English characters) IS:10718-1983 Method of dimensioning and tolerancing on technical drawings IS:11667 1991 Technical drawings - Linear and angular tolerancing - Indication on drawings IS:11669 -1986 General principle of dimensioning on technical drawings IS:8000(Part1)-1985 - Geometrical tolerancing on technical drawings (part 1: Tolerancing of form, orientation, location and run-out and appropriate geometrical definitions)

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Engineering DRG practice

BIS standards for technical DRG:

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IS:8000 (Part2)-1976 - Geometrical tolerancing on technical drawings (part 2: Maximum material principles) IS:8000 (Part3)-1985 - Geometrical tolerancing on technical drawings (part 3: Dimensioning and tolerancing of profiles) IS:10721 1983 - Datum and datum systems for geometrical tolerancing on technical drawings IS:11158-1984 - Proportions and dimensions of symbols for geometrical tolerancing used in technical drawings IS:2709-1964 - Guide for selection of fits IS:919:1963 - Recommendations for Limits and Fits for Engg IS:3073 -1967 - Assessment of surface roughness IS:10719 - Method of indicating surface texture on tech DRG

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Engineering DRG practice

BIS standards for technical DRG: IS: 813- 1986 - Scheme of symbols for welding IS: 10711-1983 - Sizes of DRG sheets IS: 1064 - 1961 - Specification for paper sizes.

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Engineering DRG practice

Sheet sizes

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Engineering DRG practice

DRG sheet sizePreferred DRG sheet sizes are as follows: Sheet size A0 A1 A2 A3 A4 Trimmed size in mm 841 X 1189 594 X 841 420 X 594 297 X 420 210 X 297

The surface area of two successive preferred sizes are in the ratio of 1:2. DRG sheet sides of each size are in the ratio of 1:2 The surface area of the basic size A0 is 1 sq. m

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Engineering DRG practice Preferred DRG sheet sizes

Similarity of formats

Relationship between two sides

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Engineering DRG practice

Title BlockTitle block should contain the following information: 1. 2. 3. 4. 5. 6. Title of the DRG DRG No. & sheet No. Scale Projection symbol Name of the organisation Dated initials of the personnel designing, checking, standard and approved The size of the title block is uniform for all sizes.

Note:

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Engineering DRG practice

Recommended scales for Engineering DRG:Full size 1:1 Reduced scale 1:2 1:5 1:10 1:20 1:50 1:100 1:200 1:500 1:1000 1:2000 1:5000 1:10000 Enlarged scale 50:1 20:1 10:1 5:1 2:1

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Engineering DRG practice

Grid reference on DRG sheet: It permits easy location on the DRG of details, additions, modifications etc. How & when to use Grid reference ? eg: C7 E5

1.

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Engineering DRG practice

Conventional lines and applicationsDescription Continuous - thick Continuous - thin ( Straight and curved) A B Line Applications A1 Visible outline A2 Visible edges B1 Imaginary lines of intersection B2 DIM lines B3 Projection lines B4 Leader lines B5 Hatching B6 Out lines of revolved section in place B7 Short centre line C1 Limits of partial or interrupted views and sections, if the limit is not a chain thin line D1

Continuous thin free hand. Continuous thin (Straight) with zig zags.

C D

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Engineering DRG practice

Conventional lines and applicationsDescription Dashed thick Dashed thin Chain thin E F G Line E1 E2 F1 F2 Applications Hidden outlines Hidden edges Hid