Turning

Typical Parts Made with These

Processes

Machine Components

Engine Blocks and Heads

Parts with Complex Shapes

Parts with Close Tolerances

Externally and Internally Threaded Parts

Products and Parts Made By These

Processes

Alternative Processes

Precision Casting

Powder Metallurgy

Powder Injection

Molding

Abrasive Machining

Thread Rolling

The Turning Process

Using Engine Lathes

Operate on all Types of

Materials

Use of single-point tools

Skilled Labor

Low Production Rate

Tool Geometry

Rake Angle

Side Rake Angle

Cutting-Edge

Angle

Relief Angle

Nose Radius

Typical Lathe and Its Various Components

Lathe Components

Bed: Usually made of cast iron. Provides a heavy

rigid frame on which all the main components are

mounted.

• Ways: Inner and outer guide railsn that are

precision machined parallel to assure accuracy of

movement.

• Headstock: mounted in a fixed position on the

inner ways, usually at the left end. Using a chuck, it

rotates the work.

• Gearbox: inside the headstock, providing multiple

speeds with a geometric ratio by moving levers.

• Spindle: Hole through the headstock to which bar stock can be fed.

• Chuck: 3-jaw (self centering) or 4-jaw (independent) to clamp part being machined.

• Tailstock: Fits on the inner ways of the bed and can slide towards any position the headstock to fit the length of the work piece. An optional taper turning attachment would be mounted to it.

• Tailstock Quill: Has a Morse taper to hold a lathe center, drill bit or other tool.

• Carriage: Moves on the outer ways. Used for mounting and moving most the cutting tools.

• Cross Slide: Mounted on the traverse slide of the carriage, and uses a handwheel to feed tools into the workpiece.

• Tool Post: To mount tool holders in which the cutting bits are clamped.

• Compound Rest: Mounted to the cross slide, it pivots around the tool post.

• Apron: Attached to the front of the carriage, it has the mechanism and controls for moving the carriage and cross slide.

• Feed Rod: Has a keyway, with two reversing pinion gears, either of which can be meshed with the mating bevel gear to forward or reverse the carriage using a clutch.

• Lead Screw: For cutting threads.

• Split Nut: When closed around the lead screw, the carriage is driven along by direct drive without using a clutch.

• Quick Change Gearbox: Controls the movement of the carriage using levers.

• Steady Rest: Clamped to the lathe ways, it uses adjustable fingers to contact the workpiece and align it. Can be used in place of tailstock to support long or unstable parts being machined.

• Follow Rest: Bolted to the lathe carriage, it uses adjustable fingers to bear against the workpiece opposite the cutting tool to prevent deflection.

Lathe Accessories

Carriage and Cross Slide Stops

Devices for Turning Parts with Various Tapers

Milling, Sawing, Gear-Cutting, and Grinding

Attachments

Various Attachments for Boring, Drilling, and

Thread Cutting

More Tool Geometry

Lathe Operations

Form Tools

Boring

Drilling

Parting

Grooving

Thread Cutting

Knurling

Cutting Operations Performed on a Lathe

Above Left: Example of Boring Above Right: Example of Drilling

Below Left: Example of Thread Cutting Below Right: Example of Grooving

Types of Lathes

Bench Lathes

Special Purpose Lathes

Tracer Lathes

Automatic Lathes

Automatic Bar Machines

Turret Lathes

Computer-Controlled Lathes

Turret Lathe

Computer-Controlled Lathe

Things to Remember About

Machining Parts on Lathes

Takes considerable amount of time

High Production Costs

Wastes Material

Not as Economical as Forming or Shaping

Boring and Boring Machines

What is Boring

Performed to enlarge a hole made previously.

Used for circular internal profiles in hollow

workpieces

Boring Machines

Small pieces – lathe

Large pieces – boring mill Horizontal vs Vertical

Boring mills Perform various

operations: TURNING, FACING, GROOVING, CHAMFERING

Horizontal Boring Mill

Vertical Boring Mill

Large pieces can be

machined on a vertical

mill

Jig Boring Machines

Vertical machines

High precision bearings

Used to make jigs and

fixtures

Being replaced by CNC

boring machines

Considerations

Through holes, rather than blind holes,

should be specified.

Smaller length-bore diameter ratios

Interrupted internal surfaces should be

avoided.

Milling and Milling Machines

Milling

The Process of cutting away

material by feeding a

workpiece past a rotating

multiple tooth cutter.

Types of Milling

Peripheral Milling

Peripheral Milling is when the cutter is longer than

the width of the cut.

a.k.a.- Slab Milling

The axis of the cutter is usually parallel to the work

piece surface.

Face Milling

the cutter is mounted on a spindle having an

axis of rotation perpendicular to the

workpiece surface.

Leaves feed marks on the machined surface.

End Milling

The cutter generally rotates on an axis

vertical to the workpiece.

It can be tilted to machine tapered surfaces.

Cutting teeth are located on both the end

face of the cutter and the periphery of the

cutter body.

Can produce a variety of surfaces at any

depth.

Conventional Milling

a.k.a- Up Milling

The Direction of cutter rotation opposes the

feed motion.

Climb Milling

a.k.a.- Down Milling

The direction of cutter rotation is the same as

the feed motion.

Other Types of Milling

Straddle Milling

Form Milling

Slotting and Slitting

Uses circular cutters

Tool holders

Arbor Cutters

Mounted on an arbor

Used in peripheral, face, straddle and form

milling.

Shank-Type Milling

Cutter and shank are

one peice

Design and Operating Guidelines

Basic cutters should be used as much as possible.

Avoid expensive special cutters.

•Chamfers should be specified instead of

radii.

•Chamfer-A furrow or groove, as in a column.

•Avoid internal cavities and pockets with sharp

corners.

•Due to the difficulty of doing them.

Troubleshooting

Tool Breakage Tool material lacks toughness,

improper angles.

Excessive Tool Wear improper tool material, improper

tool fluids.

Rough Surface Finish Feed per tooth too high, tool

chipped or worn.

Chatter Marks Insufficient stiffness of system,

external vibrations.

Breakout Lead angle too low, feed and

depth of cut too high.

Milling Machines

First Milling Machine

Built in 1820 by Eli Whitney

Column-and-Knee type

Most common milling machines.

Basic Components

Work Table

Saddle

Knee

Overarm

Head

Bed Type

Work table is mounted is mounted directly on

the bed.

Not versatile

High Stiffness

Used for high production work

Other Milling Machines

Planer-Type Several heads and cutters able to mill different surfaces

•Rotary-Table

•One or more heads for face milling.

•Computer Numerical Control

•Able to mill, drill, bore and tap with repetitive accuracy

•Profile Milling Machines

•5 axes of movement.

Planning and Shaping

Planning Large workpieces 25m X 15m

Work piece is mounted on a table and travels back and

forth along a straight path.

Cutting speeds can get up to 120 m/min with 150 hp

Shaping Tool does the moving

Small less than 1m X 2m

Gear milling

Uses a rotating form

cutter

Gear blanks are

indexed after each cut

Is a low production

process

Gear teeth are

produced individually