11/01/2009 - 12/01/2009 - Mechanical engineering
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Friday, November 27, 2009

The safe use of machine tools

The safe use of machine tools

Personal safety

• Do not use a machine unless you have received instruction in its
operation.
• Do not use a machine without the permission of your instructor or
supervisor.
• Do not lift heavy workpieces or workholding devices onto a machine
without assistance or without using the mechanical lifting equipment
supplied.
• Do not lean on a machine whilst it is working.
• Do not wear rings on your fingers whilst operating a machine. They
may get caught in it.
• Do not place tools and measuring equipment on the headstock of a
lathe where they may fall into the revolving chuck.
• Do not attempt to remove swarf with your bare hands – use the rake
provided.
• Always wear overalls in good condition and keep them buttoned up
so as to prevent any loose clothing becoming caught in any moving
machinery. Keep your sleeves rolled up or keep the cuffs closely
buttoned at your wrists.
• Always wear safety goggles when cutting is in progress.
• Always wear safety boots or shoes.
• Always adopt a short hairstyle or keep your hair covered in a suitable
industrial cap.
• Always use a barrier cream to protect your skin.
• Always report accidents no matter how small.


Machine safety

• Do not attempt to change tools on a lathe whilst the work is revolving.
• Do not remove stops, guards or safety equipment or adjust such
devices unless, as part of your training, you do so under the direct
supervision of your instructor.
• Do not change the spindle speed whilst the machine is operating as
this will cause considerable damage to the gearbox.
• Do not change the direction of rotation of a machine whilst it is
running.
• Do not leave your machine unattended whilst it is running.
• Always keep the area around your machine clean and tidy and clear
up oil and coolant spills immediately.
• Always clean down your machine when you have finished using it.
• Always make sure you know how to stop a machine.
• Always isolate a machine when changing cutters and workholding
devices and loading or unloading work.
• Always stop the machine and isolate it when anything goes wrong.
• Always switch off the machine and isolate it before leaving it at the
end of your shift.
• Always check oil levels before starting the machine.
• Always check that workholding devices are correctly mounted and
secured before cutting commences.
• Always check that the work is securely restrained in the workholding
devices before cutting commences.
• Always make sure the machine is set to rotate in the correct direction
before setting it in motion.
• Always make sure any automatic feed facilities are turned off before
setting the machine in motion.
• Always clean and return tools and accessories to their storage racks
or to the stores immediately after use.
• Always use the correct tools, cutters and workholding devices for the
job in hand, never ‘make do’ with a makeshift set-up.
• Always check that the cutting zone is clear of loose tools, clamps,
spanners and measuring equipment before starting the machine.
• Always stop the machine and report any mechanical or electrical
defect immediately to your instructor.


Safety is largely a matter of common sense. Never become complacent
and take risks to save time. Safety should become a way of life
at home and at work. Accidents are always waiting to happen to the
inattentive, the careless and the unwary.
Terminology of measurement

Terminology of measurement

Indicated size

This is the size indicated by the scales of a measuring instrument when
it is being used to measure a workpiece. The indicated size makes no
allowance for any incorrect use of the instrument, such as the application
of excessive contact pressure.

Reading

This is the size as read off the instrument scales by the operator. Errors
can occur if the scales are misread, for example sighting (parallax) errors
can occur when measuring with a rule. Vernier scales are particularly
easy to misread in poor light. A magnifying lens is helpful even in
good light and even if you have good eyesight. Electronic measuring
instruments with digital readouts overcome many of these reading difficulties.

Reading value

This is also called the ‘reading accuracy’. This is the smallest increment
of size that can be read directly from the scales of the instrument. It
will depend upon the layout of the scales. A micrometer caliper normally
has a reading value of 0.01 millimetre. A bench micrometer fitted with
a fiducial indicator normally has a reading value of 0.001 millimetre. A
vernier caliper with a 50 division vernier scale normally has a reading
value of either 0.01 millimetre or 0.02 millimetre depending upon how
the scales are arranged.

Measuring range

This is the range of sizes that can be measured by any given instrument.
It is the arithmetical difference between the largest size which can be
measured and the smallest size which can be measured. For example,
a 50 mm to 75 mm micrometer has a measuring range of 75 mm −
50 mm = 25 mm.

Measuring accuracy

This is the actual accuracy expected from a measuring instrument after
taking into account all the normal errors of usage. It can never be better
than the indicated size.

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