1. Shop Safety with the Machine Lathe
Introduction
The machine lathe is a very important tool. It is said that the lathe is capable of
producing all other machine tools because it can perform a great variety of operations. But the
lathe is also a very dangerous machine as there are a lot of high speed moving parts. It is
paramount that the lathe is operated at all times to prevent injury and possible death. This report
is intended to help you operate the machine lathe safely.
1.0 Function of the Machine Lathe
1.1 Principle of operation
All the lathes in the shop are driven by electric motors that, through gearing, rotate a
chuck holding the piece of metal (stock) to be turned. The gearing in the newer models are tooth
to tooth connected, while the older models are belt connected. By shifting gears you can produce
different speeds of rotation for the chuck. The speeds required are determined by the type of
material, operation, and type of cutting being done.
The metal is mounted and secured in a 3 or 4 jawed chuck. Prior to turning the lathe on,
the chuck is rotated by hand to ensure freedom of movement. Longer pieces, like shafts, are
supported by a turning centre also known as a live centre or a dead centre, one that can not turn,
in the tail stock (Fig. 1) during cutting. For additional support a steady rest and a follower rest
can be added to the lathe (Fig. 2). The tail stock can also mount drills as well as centres.
The lathe carriage (Fig. 3) is the centre of the operation and is where the carbon tool bit is
mounted in the tool rest. In our shop, the supervisor will grind these tool bits for our use or help
you to grind one that is needed. Tool bits are used for cutting, facing, parting, boring, and
threading. Each one is used for a different specific operation, for example the Roughing Tool bit
is used to take deep cuts and removing most of the stock material, the V-Type Threading tool is
used for threading, and there are many more different bits (see Fig. 4). After the tool bit needed
is ground, it is mounted into the tool mount or a turret on the carriage. The carriage moves the
length and width of the lathe and the tool rest can be moved on an incline for cutting. It can be
moved either automatically, by internal gearing attached to the carriage and controlled by the
lathe speed and feed rate, or by manual hand control done by turning control knobs specific for
direction.
1.2 Typical parts and shapes which can be machined
A lathe can face end pieces flat or make a cubed piece by facing all sides. Cylinders or
tubes can be shaped by the long cutting of a stock piece utilizing lathe feed to move the carriage
and then drilling the centre out. Internal and external threads can be cut by boring, or by cutting
using specific speed and rates of cut. Taper cuts are done using an inclined setting on the
carriage. Specific combinations of methods can produce crankshafts, bolts, nuts, cylinders,

2. eccentric cams, and more. Surface measurements are very important here for flat and square
positioning of pieces, to ensure a quality finish.
2.0 Safety Considerations
2.1 Preparation and set up
Before starting, be sure that you wear safety glasses. If you forget your own, an extra
pair can be found at the shop door. Ensure you have no loose clothing, hanging items such as
jewellery, or dangling hair (use a hair net). Be familiar with the equipment before you start
using it and know what you want to do.
Begin by mounting your piece in the lathe chuck. Always remove the chuck key after
use and never take you hand off of the key while it is in the chuck. Turn the chuck to check for
freedom of movement and clearance of tool rest, chuck jaws, and lathe parts.
Determine your required speeds and set the gearing. Finding the turning centre of your
piece by hand rotating the chuck and set the tool bit to cut, with rotation into the bit, just a little
lower than centre. Move the cutting bit out and position it for stock cutting. Ensure the machine
is in neutral before engaging the drive and know where the emergency STOP button is located.
All this is done before turning on the power. If you are unsure of anything, ASK FOR HELP.
2.2 Operation
Ask the shop supervisor if the speeds, and the long and cross feeds are correct. If the
machine is belt driven (Fig. 5), it is possible to start the machine in neutral and then engage the
drive. The chuck will not spin until the drive is engaged. If the lathe is gear driven, then the
machine must be put into the correct speed setting before being turned on. If a different gearing
is required, wait until the chuck comes to rest before changing gears.
As cutting is taking place, long pieces of metal will stream off (Fig. 6). Do not grab or
pull these as they are sharp and often hot. The piece may also pull back which can cut badly if
you are holding the metal cutting. In high production or very fast cutting cooling fluid is used to
lubricate and cool. In our shop, since we do not make deep or fast cuts frequently, we usually
will not use cooling fluid. However, we will use fluids like oil when doing a deep cut or a
special operation like knurling or boring.
2.3 Clean up
After you are finished cutting, shut off the lathe and remove your piece from the chuck.
Do not take you hand off the chuck key while the key is in the chuck. Remove the tool bit.
Clean all cuttings and deposit them in a scrap metal bin. Do this by brushing off the lathe
carriage, tail stock, and bed with a brush. Using gloves pick the pieces out of the bottom tray. If
cooling fluid was used, most of it will drain into a reservoir. Clean the remainder up with rags.

3. 3.0 Safe Machine and Tool Operating Parameters
Only use the lathe for what it is intended, cutting rotating metal, facing or drilling. When
operating the lathe use the proper speed, long and cross feed settings, as determined by the
proper charts and tables. Never distract anyone using a lathe or interfere with its operation. If at
any time you are unsure, do not know, or need help, ask the shop supervisor.
4.0 New Developments (recent improvements)
The lathes in our shop are older models, newer models have CNC (Computer Numerical
Control) ability; these are better suited for production needs and processes. Specific machining
requirements have progressed to more accurate measurement by digital readings and control,
compared to calipers and scales.
5.0 Environmental Concerns
5.1 Lubricant use and disposal
The lathe is lubricated internally on a regular maintenance schedule. For our cutting
purposes we only need to be concerned with cooling fluid. This is, for the most part, recycled
when it drains back to its reservoir. Rags used in clean up are disposed of in specific, noted
containers.
5.2 Chip disposal and recycling
During clean up all chips and cuttings are to be put in a scrap metal container for
recycling. The same applies to scrap stock.
5.3 Used tool disposal or refurbishing
Tool bits can be re-sharpened or reground for continual use. Broken tool bits or unusable
took bits are disposed of in scrap containers as indicated.
6.0 Information for Design of Parts for Safe Machining
6.1 Pre-processing of parts
Before you start cutting, a lot of thought should be put into what you are doing and what
your next step is. For example, there is no sense in heat treating your part only to machine off
the heat treated surface in the next step. You should always work from the rough details into the
fine details, such as turning your part down then cutting or drilling. This should help to prevent
crushed or misshaped parts. Work smarter not faster.

4. 6.2 Post-processing of parts
It is in this step where you will do the finishing touches. Be careful that all your work is
not ruined with one wrong move. As mentioned earlier, removing burrs could remove that
valuable heat treated surface. Also, handling of mild steel can cause quick corrosion so
precautions should be taken to prevent this. Protect your piece from damage to carefully made
corners and edges. Dents can cause miss-fitting and leaks or incorrect tolerance levels.