Lab Module Lathe Ent 144

7/28/2019 Lab Module Lathe Ent 144

1/13

ENT 144/2 Machining Skills Laboratory Module

1

LATHE MACHINE

1. OBJECTIVE

Understand the machine mechanism and various types of cutting tool

Understand what is chips and types of chip produce during experiment

Be able to operate the machine to produce finish product from the raw material

2. INTRODUCTION

Turning is the process of machining external cylindrical and conical surfaces. Lathes are

machine tools designed primarily to do tuning, facing and boring. It can also do drilling

and reaming. Very little tuning is done on other types of machine tools, and none can do

it with equal facility.

The turning operation is dependent upon the following variables:-

(a)different lathes

(b)different tools

(c)different material


2/13


2

Figure 1: Lathe nomenclature.

Figure 2: Lathe Controls

2.1 MACHINE STRUCTURE

2.1.1 Lathe Bed

The lathe bed rests on the base. It provides the foundation to which the headstock is

attached and serves as the guide way for the tool carriage and tailstock.

2.1.2 Headstock

The headstock holds the headstock spindle. It is supported at both ends and is designed as

a hollow shaft so as to accommodate bar material when required. At the front of the

headstock there is tapered hole designed to receive the lathe centers. The headstock

houses the back gear (with speed change mechanism for slow and fast operation) and the

reversing mechanism (designed to change the direction of feed without changing the

direction of rotation of the lathe).


3/13


3

2.1.3 Lathe Chuck

The lathe chuck is used to hold work piece and it is fitted to the spindle nose to hold and

drive the work piece.

2.1.4 Quick-Acting collect Attachment

It is mounted on the flange at the main spindle end.

2.1.5 Tool Carriage

The principle components of the tool carriage are:-

Figure 3 : Tool carriage

1. saddle2. cross-slide3. compound slide (tool rest)4. tool holder or tool post

Two spindles are mounted on the front of the lathe bed to provide the mechanical feed ofthe tool carriage.


4/13


4

2.1.6 The Apron

Figure 4: The Apron

The lead screw (6) and the feed shaft (7) provide the longitudinal and cross feed as well

as the feed action necessary to cut screw threads. The feed shaft being used for the first

two functions and the lead screw for the latter. The reversing lever (9), which provided to

change the direction of movement, is attached to the apron (8).

2.1.7 The Tailstock

Figure 5: The tailstock


5/13


5

It serve to support the free end of work piece held in a chick, or for housing the tailstock

center, or as a tool holder for drills, reamers, etc.

It can be moved back and forth along the lathe bed and using the clamping lever (7)

together with the clamping plate (10), it can be locked at any point along the way.

The tailstock is composed of a base (1) and a main body casting (2). For turning between

centers the tailstock and headstock centers must be in perfect alignment.

For the purpose of setting up the machine for cylindrical or taper turning operations, the

tailstock is designed so that the main body can be adjusted transversely relative to thebase by means of adjusting screws (9). The main body houses the tailstock barrel (3)

which can be moved in the longitudinal direction with the aid of the handwheel (8) and

the feed screw (5) to permit infeed when boring and reaming. The tailstock barrel is

designed to receive either the lathe center (4) or a tool with a Morse taper. For turning

between centers, the barrel is secured in place by means of the forward clamping lever

(6).

2.1.8 Steadies

When long, thin work piece are turned, the cutting pressure applied by the cutting tool

produces bending which causes the work piece to be out of round and to have a rough

surface. This can be avoided by using the steady.


6/13


6

2.2 OPERATING ELEMENTS

Figure 6: Lathe machine operating elements

1 Turning knob for speed selection

2 Turning knob for speed selection with cached idling position

3, 4, 5 Turning knobs for feed rates respectively thread pitches

6 Turning knob for feed reversing gear

7 Lever for switching ON and OFF the automatic feed motions, also for pre-

selection of the feed direction longitudinal or transverse

8 Catch in lever for apron nut

9 Release knob for catch in lever

10 Hexagon screw for bedslide clamping

11 Setting disk for feed power

12 Pull knob for oil pump

13 Operating lever for quick acting collect attachment

14 Push knob on quick acting collect attachment lever


7/13


7

15 Main switch

16 Safety type switch lever for main spindle

3. FORMULA

The cutting speed is the distance in meters traveled by a point P on the circumference of

the work piece one minute (rev/min).

Figure 7: Cutting speed

The basic factors are:-

V = cutting speed in meter per minute

n = speed of the work in revolutions per minute (rev/min)

d = diameter of the workpiece in mm

= 3.14

The formula for the calculation of the cutting speed is:

V = d x x n m/min

1000

For maximum speed:

V= DoN

For average speed:


8/13


8

V= DavgN

WhereDo = original diameter

Davg = average diameter

In order to be able to work economically it is important to select the cutting speed best

suited to the job.

The selection of the proper cutting speed is influenced first of all by the machine, but also

by the following factors:-

1. the material to be worked (hard, soft)

2. the material from which the tool is made (tool, steel, carbide)3. the type of cutting operation (roughing, finishing)4. the type of cooling

Turning refers to cutting as shown below.

Figure 8: Basic principle of the turning operation


9/13


9

Figure 9: Chip formation showing the deformation of the material being machined.

Cutting ratio, r

Where to= thickness of the chip before prior to chip formation

tc = thickness of the chip that formed along the shear plane.

Material Removal Rate (MRR) is the volume of material removed per unit time, can be

obtained from the equation:

MRR =()(Davg)(d)(f)(N)

Where Davg =2

fo DD

Do = original diameter

Df = final diameter

d = depth of cut

f = feed

N = rotational speed of the workpiece

The cutting time, tcan be obtained by the equation below:

r =c

o

t

t


10/13


10

t=fN

l

Where l = length

f = feed

N = rotational speed of the workpiece

Torque can be obtained from this equation:

Torque = (Fc) (Davg/ 2)

Where Fc = cutting force

Davg = average diameter

Power can be obtained from this equation:

Power =(Torque) ()

Where = 2 N

Cutting power,Pccan be obtained from this equation:

Pc= FcV

Where Fc = cutting force

V = cutting speed

Unit power,Puis power per unit volume rateof metal cut. Unit power is also known as

specific energy, U.

U =Pu=MRR

Pc =wVt

VF

o

c =wt

F

o

c


11/13


11

Where w= width of cut

4. EQUIPMENT / APPARATUS

1. Workpiece diameter 40 mm x 160 mm

2. Lathe machine with accessories such as tool post, drill chuck, etc.

3. Safety attire such as goggles, safety jacket, etc.

4. Cutting tool

5. Knurling tool

6. Grooving tool

7. Drill

8. Vernier caliper for measurement

9. Setting gauge

10.Thread gauge

* Please refer to the Standard of Procedure (SOP) that have been provided in the

laboratory.


12/13


12

Drawing of Lathe Machine Project for Machining Skils


13/13


13

5. QUESTIONS

1. What are the parameters that are important in turning operation?

2. In your own words, give the definition of the terms below. You may also include

figures to explain:

a. Machinability

b. Turning

c. Facing

d. Boring

3. Why coolant/cutting fluid is important in turning or milling operation? And

explain how it could affect the surface finish?

Lab Module Lathe Ent 144

Documents

Transcript of Lab Module Lathe Ent 144