Lecture 8 Lathe Machine fundamentals Sunday, October 25, 2015Lathe Fundamentals 1

Lecture 8

Lathe Machine fundamentals

Thursday, April 20, 2023Lathe Fundamentals

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SafetyThursday, April 20, 2023Lathe Fundamentals

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Respect the machines

Common Sense

• Wear safety glasses• Avoid loose clothing• Restrain long hair• Never wear gloves• Never wear shorts or sandals• Remove Necktie• Stay alert

Lathe - IntroductionThursday, April 20, 2023Lathe Fundamentals

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The Basics• The lathe is one of the most common machines found in today’s modern machine shop. Used primarily to produce cylindrical workpieces.

• Different from a mill in that it produces a round diameter on a part by rotating a workpiece against a non-rotating single-point tool, as Figure 1. shows.

• The lathe, operated manually, changes the size, shape, and finish of a workpiece with a variety of cutting tools.

Fig. 1


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Types Of Lathes The three types of lathes you may find in a machine shop today are:• Engine Lathe

• The original lathe is the engine lathe, shown in Fig. 1.• This type of lathe positions and holds a workpiece on a desired centerline, while the spindle rotates the workpiece.• As the workpiece spins, the cutting tool gradually passes along the surface of the workpiece, and a layer of material is removed.• Engine lathes are the most frequently used manual lathes.

Fig. 1


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Types Of Lathes Turret Lathe & CNC Machining Centers

• The turret holds multiple cutting tools that rotate into position when needed. Each time the turret lever is activated, the turret spins and positions the next tool in the sequence. It is then ready to carry out different machining operations.• Because the turret holds multiple tools, the machinist does not have to change tools each and every time a different tool is needed. There are automated versions of these lathes that are computer controlled and are called CNC Machining Centers.

CNC Machining CenterTurret


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Types Of Lathes CNC – Lathes• Today, many shops use CNC lathes, like the one in Fig. 1. • A CNC lathe is a type of lathe that uses computer numerical controls (CNC) to operate the lathe. These machines use single bit tooling.

Fig. 1

Basic Lathe TerminologyThursday, April 20, 2023Lathe Fundamentals

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Headstock

Chuck

Ways

Tailstock

Feed Gear Box

Cross Slide

Tool Post

Carriage

Brake – Emergency

(E) Stop

Compound Rest

Lead screw

Bed

Basic Lathe Terminology

Parts Of A Lathe• The bed is the base and backbone of the lathe. The bed is a heavy, rigid frame made of cast iron on which all other components of the lathe are mounted and/or move.

• The ways are parallel, longitudinal rails located on the bed. There are two sets of inner and outer ways. The ways guide other components on the lathe, such as the tailstock.

• The headstock is mounted on the inner ways and provides the power to rotate the workpiece. It consists of a hollow spindle and a set of gears that rotate the spindle at a range of speeds that are operator adjustable


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Parts Of A Lathe• The spindle is mounted in the headstock and carries the work holding devices, i.e. – chuck. The spindle has a hole extending through its length, through which a long bar stock can be fed. The size of this hole determines the maximum diameter of bar stock that can be machined when the materials must be fed through the spindle.

• The tailstock is located opposite of the headstock and supports the end of longer workpieces. The tailstock typically contains a center that holds the other end of the workpiece in place, but it can also hold a cutting tool, by way of a drill chuck.


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Parts Of A Lathe

• The carriage is the section of the lathe that slides along the ways and supports the cross-slide and cutting tool. The carriage contains the compound rest, which permits angular adjustment of the cutting tool. The compound rest can rotate with respect to the cross-slide, which permits further positioning of the tool being used.

• The leadscrew powers the carriage assembly. The leadscrew is a large, threaded rod that is located below and parallel to the ways.


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Indicating Dial indicator

• Can be attached to bed whendigital readout is not present (Z axis travel indicator)• Used to indicate in a work piece when using a 4 jaw chuck – a magnetic indicator stand can be used to hold the indicator.


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Tooling Collets – Work Holding

• Collets run more true than a chuck Drill Chuck – Tool Holding

• Mainly for drill bits• Mounts on a Morse Taper arbor (1 thru 4 most common)• Slides into tailstock

Collets – Work HoldingMorse Taper

Drill Chuck – Tool Holding


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Tooling

Center Drill – used first• Keeps holes accurately positioned

Twist Drill

Reamer• A tool for widening or shaping holes• Precise hole size

Boring Bar – Boring Holes

Lathe Tool Bits – Facing – Turning – Threading - Grooving


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Tool Post & Holder

Tool holders slide down onto tool post Twist handle to lock and release tool holders


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Work Holding Devices Chucks – 3 And 4 Jaw Chuck

• The most common device used to hold and position parts on the lathe is the chuck. A chuck consists of three or four jaws that clamp down on the end of the workpiece. • The most commonly used chuck has jaws that open and close together automatically centering the workpiece. Chucks are mounted to the lathe spindle using the two most common methods – Spindle Nose with Long-Taper Key Drive (L-Series) & the Cam-Lock Spindle (D-Series)

Cam-Lock Spindle - Victor

Long-Taper Key Drive - LeBlond

Long-Taper WrenchCam-Lock Wrench

Threaded Collar


Work Holding Devices

3 Jaw Chuck• The jaws open and close together automatically centering the workpiece.

• This kind of chuck usually has a 2 piece reversible set of jaws, or a complete other set, one set holds the larger work while the other set holds rings and small work.

• These 3 jaw universal chucks when in good shape center work accurately to within .002 to .003. 3 Jaw – Solid Jaw (2 Sets)

3 Jaw – 2 Piece Reversible

Chuck (key) Wrench


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Basic Lathe Terminology Work Holding Devices

4 Jaw Chuck• The 4 jaw independent chuck has four jaws and each must be moved separately with a chuck wrench; it is used mainly to hold work that is not perfectly round. • It may be used to hold work that is round, square, rectangular, or irregular in shape. This chuck is more accurate since the work can be centered with the use of a dial indicator.• The jaws on this kind of chuck are solid reversible; that is, they can be taken out and put on again in the opposite direction or a 2 piece reversible jaw. They have steps so that different sizes of work can be held. There are also 4 jaw self centering chucks available.

4 Jaw – 2 Piece Reversible Jaws

4 Jaw – Solid Reversible Jaws


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Basic Lathe Terminology Cutting

• Facing• Turning• Boring• Taper Turning• Center Drilling• Parting – Grooving• Hole Tapping• Knurling (a small projecting knob or ridge)• Threading Tapered

Faced

TurnedParted Necked


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Feeds and Speeds (F/S)

Spindle Speed: • Speed (rpm) that the spindle and/or chuck rotates

Tool Speed:• [in/min] or [mm/min]: How fast the carriage is moving (Z axis)

Feed Rate:•[mm/rev] relative speed of tool and spindle


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Cutting Tools

• The most common cutting tools used are made from materials such as high-speed tool steels (HSS) and carbide. (a compound of carbon with metal or other element)

• Most tools made from these steels are single-point tools, which means they contain a single cutting edge. Single-point tools, shown in Fig. 1 and in the next slide, are the most popular cutting tools used on the lathe – hand ground HSS or the tools shown in Fig. 2 which are Brazed-tipped cutting tools.

• These tools are made from inexpensive material with a tip of more expensive cutting material brazed onto the cutting end. These materials include most commonly a C2 or C6 carbide. Carbide tooling can cut many materials at speeds up to four times faster than HSS. C2 – used for non-ferrous metals and C6 used for tougher to machine ferrous metals.

Hand Ground HSS Tool Bits

Brazed Tip Carbide Tool BitsFig. 2

Fig. 1


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Cutting Tools – Single PointThursday, April 20, 2023Lathe Fundamentals

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Left-Hand Thread Cutting 60deg Right Hand

Cuts Left To Right Cuts Right To Left

A cutting tools tip should be set to the centerline of the workpiece

Cutting tip

Height Adjustment Screw For Tool Holder & Tool

Cutting Tools – Carbide Inserting Tooling


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• Shops also use replaceable cutting inserts.

• Cutting inserts come in a variety of shapes, as you can see below.

• Inserts are secured in a tool holder and rotated so that there is a new cutting surface in the same location.

Lathe - OperationsThursday, April 20, 2023Lathe Fundamentals

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• Changing the chuck & collet use• Facing• Turning• Center Drilling• Boring• Taper Turning• Parting – Grooving• Drilling• Hole Tapping• Knurling• Threading – using a die and holder• Reaming Tapered

Faced

TurnedParted Necked


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• Outer-diameter operations are cutting operations that occur on the outer surface of the workpiece.

• Facing - is the machining of a flat surface on the end, or face, of a workpiece. Facing is sometimes used to remove uneven, rough surfaces and burrs from a workpiece.

• Turning is the machining of the external surface of round parts. During turning, a part is held at one or both ends while it rotates against a single-point tool. The cutting edge is forced against the surface of the workpiece, cutting metal as the tool is fed along the surface.

Outer Diameter Cutting Operations


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Outer Diameter Cutting Operations• Parting - also called cutting off, involves separating a complete piece from stock. Parting is important because you can ruin the whole job if the part is not cleanly removed.

• OD grooving is a simple machining process during which a cutting tool is plunged into a workpiece to create a groove or channel. There are essentially three types of grooves: square-cut grooves, round-cut grooves, and V-cut grooves.

• OD threading - is a special turning operation that uses a single-point tool to cut spiraling ridges (threads) down the length of a workpiece. These threads are found on screws, bolts, and other types of fasteners. The lathe has the ability to cut many different types of threads with the most common being a 60 degree thread.


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Inner Diameter Cutting Operations

Lathes are also capable of performing cutting operations on the inner surface of a workpiece. Inner-diameter operations (ID) hold the workpiece on one end, while the cutting tool enters the workpiece at the other end.

• Drilling simply creates a hole in the workpiece. A drilled hole is the least accurate type of hole made.

• Boring enlarges the inner diameter of a preexisting hole. This process improves the accuracy of the hole and makes it more round. On the lathe, boring is essentially like internal turning.


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Inner Diameter Cutting Operations

• Reaming smoothes the internal surface of a hole. It uses a special multi-point tool to remove metal from inside a hole. Reaming only removes small amounts of metal. An accurate method of finishing a specific hole diameter.

• Tapping cuts internal threads into a drilled hole.

• ID grooving cuts a single circular channel or groove into a drilled hole.

Documents

Lecture 8 Lathe Machine fundamentals Sunday, October 25, 2015Lathe Fundamentals 1