The lathe can be a safe machine only if the machinist is
aware of the hazards involved in its operation. In the
machine shop, as anywhere, you must always keep your
mind on your work, to avoid accidents. Develop safe
work habits in the use of setups, chip breakers, guards,
and other protective devices. Standards for safety have
been established as guidelines to help you eliminate
unsafe practices and procedures on lathes.
SECTION I TURNING MACHINES 387
Hazards in Lathe Operations
1. Pinch points due to lathe movement. A finger caught in
gears or between the compound rest and a chuck jaw
is an example. The rule is to keep your hands away
from such dangerous positions when the lathe is
2. Hazards associated with broken or falling components.
Heavy chucks or workpieces can be dangerous when
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388 SECTION I TURNING MACHINES
dropped. Care must be used when handling them. If a
threaded spindle is suddenly reversed, the chuck can
come off and fly out of the lathe. A chuck wrench left
in the chuck can become a missile when the machine
is turned on. Always remove the chuck wrench
immediately after using it (Figures I-17 and I-18).
3. Hazards resulting from contact with high-temperature
components. Burns usually result from handling hot
chips (up to or even more) or a hot workpiece.
Gloves may be worn when handling hot chips or
workpieces. Gloves should never be worn when you
are operating the machine.
4. Hazards resulting from contact with sharp edges, corners,
and projections. These are perhaps the most common
cause of hand injuries in lathe work. Dangerous sharp
edges may be found in many places: on a long stringy
chip, on a tool bit, or on a burred edge of a turned or
threaded part. Shields should be used for protection
from flying chips and coolant. These shields usually
are made of clear plastic and are hinged over the chuck
or clamped to the carriage of engine lathes. Even when
shields are in place, safety glasses must be worn. Do
not remove stringy chips with bare hands; wear heavy
Figure I-17 A chuck wrench left in the chuck is a danger to
everyone in the shop.
Figure I-18 A safety-conscious lathe operator will remove the
chuck wrench when he or she finishes using it.
gloves and use hook tools or pliers. Always turn off the
machine before attempting to remove chips. Chips
should be broken and 9-shaped rather than in a
stringy mass or a long wire (Figure I-19). Chip breakers
Burred edges must be removed
before the workpiece is removed from the lathe.
M09_KIBB5087_09_SE_C09.QXD 6/3/09 4:00 AM Page 389
Figure I-19 Unbroken lathe chips are sharp and hazardous to
Always remove the tool bit when setting up or remov-
ing workpieces from the lathe.
5. Hazards of work-holding or driving devices. When
workpieces are clamped, their components often
extend beyond the outside diameter of the holding
device. Guards, barriers, and warnings such as signs
or verbal instructions are all used to make you aware
of the hazards. On power chucking devices you
should be aware of potential pinch points between
the workpiece and the work-holding device. Make
certain sufficient gripping force is exerted by the jaws
to hold the work safely. Never run a geared scroll
chuck without having something gripped in the jaws.
Centrifugal force on the jaws can cause the scroll to
unwind and the jaws to come out of the chuck. Keep
tools, files, and micrometers off the machine. They
may vibrate off into the revolving chuck or
6. Spindle braking. The spindle or workpiece should
never be slowed or stopped by hand gripping or by
using a pry bar. Always use machine controls to stop
or slow it.
7. Hazards associated with workpieces that extend out of
the lathe. Workpieces should be supported by a stock
tube. If a slender workpiece is allowed to extend
beyond the headstock spindle a foot or so without
support, it can fly outward from centrifugal force.
The piece will not only be bent, it will present a great
danger to anyone standing near (Figure I-20).
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