|
Purpose:
There are a few purposes or objectives in learning the lathe machine.
Firstly, the main aims are to introduce the lathe machine, identify the components of the
lathe and to learn how to handle this type of machine. Apart form that, This laboratory
session is also held to enable the students to recognize the lathe cutting tools and their
utilities. This lab also enables students to operate the machine and vary its capabilities
to perform various task in order to produce a part.
Equipment:
Lathe Machine
Lathe machine is a machine that removes materials by rotating the work
piece against a sharp single point cutter. In the operation, parts are held between
centers, attached to a faceplate, supported in a jaw chuck, or gripped in a draw-in chuck
or collet. Although this machine is suitable in turning cylindrical work, it is also used
for other operations. Plane surfaces can be machined by supporting the work in a faceplate
or chuck. Work held in this manner can be faced, centered, drilled, bored, or reamed where
the tool is approached from the end or "face’’ of the stock. In addition, a
lathe can knurl, cut threads, or turn tapers. There are several type of lathe machines
such as engine lathe, turret lathe, numerical-controlled turret lathe, vertical turret
lathe, automatic vertical multistation lathe, automatic lathe, automatic screw machine,
multispindle automatic and duplicating lathe.
Components
The lathe machine consists of several basic components, which have
their own functions that are important to help the machine operator to perform their work
effectively. The main parts are:
- Headstock
- Tailstock
- Carriage
- The bed
Headstock
Headstock is the main part of lathe machine where it locates the
control of the lathe. The control on the side of the headstock allows selection of any one
of many speeds that are arranged in logical geometric progression. This is also where the
speed control is place, this machine could spin from 40 to 2500 rpm (rotations per
minute). There are 2 switches to control the speed rotation, which needs the right
combination for the right speed. Next, there is chart to determine the measurements needed
to form a product, for instance, in thread cutting – the chart shows the correct
tools to make a exact cut on each thread. In order to determine it, we have to know the
diameter and the pitch . The ‘British Standard’ system is used in this scale
like B.S.F. (British Standard Fine )& B.S.W. (British Standard Wide ) to know how many
pitches in an inch and not forgetting the ‘metric’ system to determine the
distance of each pitch on the threads . Several other controls are the auto and manual
movement levers, the clockwise and anti-clockwise rotation switch, the thread initializer
switch and others.
This is also where the chuck, which is used to clamp the material that
needs working. When the material is clamped to the chuck, pulling the start levers will
create a rotation to the chuck along with the material, actually the rotating part of the
machine is called the ‘spindle’. More about the start levers, they can be pushed
up and down to determine the clockwise or anti clockwise rotation.
Tailstock
The tailstock can be moved along the bed of the lathe to accommodate
different length of stock. It is very important to support a material that is very long.
It is commonly provided with a hardened ball-bearing center, which may be moved in and out
by wheel adjustment. The tailstock can be adjusted in and out with respect to the
centerline of the bed. This allows for adjusting the alignment of the centers and for
taper turning. A ball bearing center rest is placed at the tailstock could be joined
together with the material at the end a will prevent further vibration. There is a lever
used to tighten the ball bearing center rest, also, the tailstock could be moved forward
or backward, so another lever is introduced to lock the tailstock in its position.
Another utility for a tailstock is that we can put a drill bit to drill
the end side of a material. It is to create a hole in the middle of the cylinder bar.
However, using a proper drill is more effective than using this method. Besides the drill
bit, other cutting tools can be incorporated or joined to the tailstock if possible.
Carriage
Carriage is a constituent where most of the shaping tools such as
cutter, facing tools, and reamers are placed. The carriage assembly includes the compound
rest, tool saddle and apron. Since it supports and guides the cutting tool, the carriage
assembly must be rigid and constructed with accuracy. Two-hand feeds are provided to guide
the tool on a crosswise motion. Obviously, these feeds can be power controlled as well.
The upper-hand wheel or crank controls the motion of the compound rest, and since this
rest is provided with a swiveling adjustment protractor, it can be adjusted for various
angle positions for short taper turning. A third hand wheel moves the carriage along the
bed, usually to pull it back to the starting position after the lead screw has carried it
along the cut. The portion of the carriage that extends in front of the lathe is an apron.
An apron is a double-walled casting, which contains the controls, gears, and other
mechanisms for feeding the carriage, and cross slide by hand or power. Usually, there are
3 wheels to control movement vertically, horizontally, and the other one is for the
carriage (when the carriage is angled than its natural square position for example, 40
degrees – this will move the carriage according to the angle and not horizontal and
vertical). This part is called the ‘Apron’.
Apart from that, it could be also turned around in different angles so
that cutting is not limited to a straight cut using the ‘rocker’. The rocker can
be rotated to adjust the cutting edge of the tool to the required height. There is a metal
scale in the middle of the carriage to see the accurate angle needed. Screwing onto it can
place cutting tools and there are about 8 screws to tighten the tools in all 4 directions.
On the top most point, there is a lever to lock or unlock the movement of the top most
part of the carriage called the ‘quick change’. This whole top section of the
carriage is called the ‘toolpost’.
The Bed
The bed and base comprise of the lower part of the machine. It is the
base and the frame of the lathe. It is also a part where all the metal chips and junks
being placed when the material is being removed during the lathe operation.
Procedure:
During the lab session, we were instructed to produce a sort of
cylindrical ring using various operations that can be done by the lathe machine such as
facing, centering, drilling, knurling and reaming. Before we began our task, our
instructor, Mr. Kamaruddin Ali briefed us in detail about the project and demonstrated us
how to handle the lathe machine. Apart from that, he always reminded us about the safety
precautions throughout the period of operation.
Safety Precautions
Here are some precautions before handling the lathe machine. Make sure
that you have all the personal protective equipment (especially the goggles) recommended
by OSHA to use and they are safe to be used. Wearing goggles are important to protect our
eyes from any metal chips produced during the operation. Put them in one side altogether
on a piece of cloth so you can see them clearly. Switch on the machine and adjust the
speed required for cutting properly. Make sure you know where is the emergency ELCB to cut
off the electricity if any accidents or unsafe conditions occur. If we are not sure about
the correct method of handling, we should consult En. Kamaruddin to get better explanation
and guidance. |
|