Machining Module 5: Lathe Setup and Operations

Parallel (Straight) Turnning

Parallel turning is to move the cutting tool parallel to the longitudinal axis ofthe workpiece in order to reduce its diameter.

Right Hand turning tool

• It has cutting edge on left side• It moves from right to left

Roughing and finishing operations

Rough Turning

• Rough turning is used to remove most of the excess material as quickly as possible to reduce the work diameter.

Finishing Turning• Is to bring the workpiece to

the required size and to produce a good surface finish.

Mount the work piece

Mount the work securely in a threejaw universal chuck, with no morethan three times the diameterextending beyond the chuck jaws.

Drilled Centre could beused to help in accuratelycentering the workpiece by usingthe tailstock

Setting the machineSet the cutting tool to the center by using tail stock

Set the turning speed within arange of (350 – 400 RPM)

Taper TurningA process used to increase or decrease the diameter ofthe workpiece in a uniform rate.

Taper angle calculation

Taper angle (α) = 45

Taper angle calculation

• Tan α = opposite / adjacent • Opposite= 40-20 /2 = 10• Adjacent = 16• Tan α = 10/16 = 0.625

• α = 32

How to produce taperd surface

1) Offsetting the tailstock

This method is mainly used for long tapers.

How to produce taperd surface

2) Using the compound rest

•This method is mainly used for short tapers.

•Use the compound rest hand wheel to feed the tool during taper turning cutting.

Grooving (Recessing) process:It is the process of cutting a groove to specific depth and width.

Grooving (Recessing) process:

Set the lathe to one-half theturning speed, (about 200 -250 RPM)

Recessing tool

Threading processIt is a process of cutting helical or spiral ridge.

External thread

Internal thread

Thread applications

1. To fasten devices 2. To increase force.

3. To provide accurate measurement, as in a micrometer.

4. To transmit motion; the threaded lead screw on the lathe causes the carriage to move along.

Types of threads

1. Right-hand thread:Right-hand thread is a type of threaded section onto which

a nut isthreaded (to be tightened) in a clockwise direction.

2. Left-hand thread:A left-hand thread is a type of threaded section onto which

a nut isthreaded (to be tightened) in a counter clockwise

direction.

Thread Terminology• The major diameter: is the largest diameter of the thread.• The minor diameter : is the smallest diameter of the thread.• The pitch diameter: is the diameter of an imaginary

cylinder that passes through the thread at a point where the groove and thread widths are equal.

• The pitch (P) : is the distance from a point on one

thread to a corresponding point on the next thread,.

• The angle of thread: is the included angle between the

sides of a thread

Because of the wide range of applications. Threads are designed in different forms as shown below:

Metric thread Acme thread

Another common type of thread is square thread which is used to transmit high force like screw jack.

Parts used in thread cutting1. Center gauge: used to set the threading tool at right angle with the work

2. Screw pitch gauge: Used to check the thread pitch.

3. Use quick change gear box to select the required pitch

The thread shown below is M20x1.5outer diameter= 20 mm , pitch=1.5mm, thread angle= 60, Depth =0.974

Threaded workpiece Thread on technical drawing

Thread cuttingThe tool feed must equal to the thread pitch.

Use gear box to select the required pitch.Engage the split-nut lever for automatic

feed.

Drilling is to make a hole having a specific diameter and depth in a solid material.

Drilling ProcessDrilling as shown on technical drawing.

Centre drilling is to make a small conical shape .

Centre drilling Process Centre drilling as shown on as shown on technical drawing.

Centre drilling is required for. 1. to guide the drill 2. to provide seat for tailstock centre.

Polishing:Is a finishing operation performed on the workpiece to improve the surface

quality.

Aluminum oxide abrasive cloth should be used for polishing most ferrous metals.Silicon carbide abrasive cloth is used on nonferrous metals.

Boring and parting off

Boring is the operation of enlarging a hole with a single point cutting tool

Parting off

Knurling and Grinding Knurling: it is a process of embossing a pattern on the cylindrical surface to provide a better grip .

Grinding :

can be done if the Lathe is equipped with an electric grinding attachment.