WOODWORKING MACHINES
CIRCULAR SAWS
Most fatal accidents to wood machinists happen when a piece of wood is ejected
by the saw. In addition, accidents can occur at unguarded saws through the
machinist slipping, or reaching past or over the saw to clear away waste and cut
pieces, and coming into contact with the blade. Another frequent cause of injury
is touching the saw teeth under the bench when clearing away the waste.
Circular Saws must be therefore guarded in three ways
Guards for parts below the bench.
A riving knife at the back of the saw above the bench.
A guard or the crown and front of the saw blade.
Even with these guards fitted, circular saws are still dangerous unless agreed
safe working practices are followed:Safety rules for all woodworking machinists are:
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use mechanical feeding wherever possible.
enclose all cutters and saw blades as far as practicable.
ensure all machines are well maintained.
ensure adequate lighting at every machine.
Safety rules for all persons who operate or work at woodworking
machines are:-
wear suitable clothing which will not catch in cutters or other
moving parts.
safe operating procedures must be agreed and used for each
machine.
only authorised persons who have been properly trained should
operate or work at woodworking machines.
ear defenders, eye shields and dust masks should be worn when
required.
machines must be switched OFF when not in use and isolated
before any major adjustment, cleaning or maintenance is done.
the machinist's attention must not be distracted while work is in
progress.
Revised Jan 2003
WOODWORKING MACHINES (cont.)
GUARDS
Guards are to be:rigid to prevent them touching the saw blade.
strong so that an accidental knock will not displace or bend them.
easy to adjust so that they can be set correctly.
well maintained to keep them easy to adjust, i.e. clear of
sawdust, rust and dirt.
regularly checked so that defects like stiff handles are quickly
discovered and rectified.
set to cover both sides and roots of teeth.
set as close as practicable to the timber being cut.
The saw should be fully guarded below the bench, so that hands cannot come
into contact with the blade when clearing away: the teeth can cause injury even
when the blade is stopped. Special guards should be considered for long
production runs if this would help to improve safety.
GUARD ADJUSTMENT
Wait until the blade is stationery before adjusting the guards - never use scrap
timber to slow the blade down. Not only can the hands slip during adjustment,
but the guard itself may touch the blade.
Set the saw height to suit the material being cut.
Check that the saw packaging is in good condition.
Lower the crown guard to give adequate running clearance for the teeth.
Adjust the guard rearwards so that the gullets of the down running teeth
will be covered by the extension piece.
Check that the guard is in line with the saw blade.
Position the fence and set the extension piece as close as possible to the timber
being cut. When cutting thin timber, which could prevent the correct positioning
of the guards, use a false fence of the same thickness as the material being cut.
Revised Jan 2003
WOODWORKING MACHINES (cont.)
RIVING KNIFE
The riving knife should be matched to the saw blade in use. It should be slightly
thicker than the plate of the saw to prevent the wood binding, but not so thick
that it makes feeding difficult.
The knife should be securely fixed below the saw bench and adjusted as close
as practicable to the teeth of the saw. It should be not more than 12mm from the
saw at the table and should follow the curve of the saw as far as practicable.
For a saw blade of less than 600mm diameter, the top of the knife must be not
more than 25mm below the top of the saw.
CUTTING
If the saw is sharp, the timber should feed easily with little loss of saw speed. If
excessive feeding pressure is needed the wood may jerk or snatch and hands
may come into contact with the blade.
The sound that the saw makes will tell if it is blunt or being fed too fast. The pitch
will lower if the saw slows down because it has to work too hard: the wood may
also judder. In either case, partially withdraw the timber, allow the saw to gain
speed and feed it again more slowly. If the saw is blunt, it should be changed.
Keeping saws sharp will improve production as well as reducing the risk of
accidents due to the machinist forcing the timber through. Saws should be
regularly checked and removed for sharpening before they get blunt.
The type and size of saw and the speed selected must be suitable for the wood
being cut. Too small a saw will not cut efficiently due to the low peripheral speed.
A notice specifying the diameter of the smallest saw that can be used with the
machine must be displayed: the minimum size is 60% of the largest saw that the
bench will take
Revised Jan 2003
WOODWORKING MACHINES (cont.)
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PUSH STICK
A suitable push-stick must be available at every circular saw and the machinist
should use it for all operations which would otherwise involve the hands being
close to the saw when it is in motion.
Push-sticks must be well made from hard wood, comfortable to use and suited to
the machinist. It is a good practice to chamfer the nose of the push stick on one
side and to cut the bird's mouth at right angles to the chamfer, so that a straight
push can be made with the hand clear of the fence when cutting narrow pieces.
Care should be taken to keep the nose of the push stick from being cut by the
saw, though this is sometimes unavoidable. Damaged pushsticks should be recut but discarded before they get too short to use safely.
USE OF PUSH STICK
Most of the accidents at circular saws occur while feeding the timber by hand,
particularly when the wood snatches or breaks. Injury is most frequently caused
to the machinist's hands, often with serious and permanent damage.
These accidents can be avoided by using mechanical feeding systems,
which should be adopted wherever possible. Where this is impracticable, the
following rules should be strictly observed:-
keep hands away from the saw blade at all times. The whole surface of
the bench should be treated as a NO-GO area.
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on production work, use the next piece of timber to feed the previous one
past the saw. for the last piece, or for one-off pieces, use a push-stick
from the edge of the table up to and past the saw teeth.
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use a push-stick for clearing away cut pieces and sawdust from both
sides of the saw.
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where necessary, use two push sticks, one for feeding the timber and the
other for keeping it against the fence.
Revised Jan 2003
WOODWORKING MACHINES(cont.)
CLEARING AWAY AND TAKING-OFF
The hands should never be used to clear cut pieces away from near the saw
teeth. Experience has shown that if this practice is used, then, sooner or later, a
finger or hand will be caught by the teeth, often with very serious injury.
Always use a, push stick to clear material and waste from:-
the down-running teeth which are exposed when no timber is being fed.
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the up-running teeth. The edge of a cut piece may catch in the gullet and
be flung back violently.
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the sides of the saw. Keep hands well away as sleeves may catch in the
teeth.
When another person assists the machinist in taking off cut pieces and waste, a
take-off table must be provided with its edge not nearer than 1200mm from the
up-running teeth. The taker-off must stand at this position when taking off.
DANGEROUS USES
GROOVES, REBATES AND TENONS
Cutting grooves and rebates is dangerous because:-
the wood may bind and be thrown back by the saw.
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the position of the saw is hidden when cutting and the cut may finish
unexpectedly, exposing the saw.
Cutting tenons is dangerous because the wood has only limited stability and may
easily be twisted or jammed against the saw.
These operations must only be carried out on a circular saw if saw type guards
are fitted, which effectively prevent hand and fingers touching the saw.
Revised Jan 2003
WOODWORKING MACHINES (cont.)
GOOD HOUSEKEEPING
Good housekeeping aids production as well as being an essential safety
requirement.
Keep the area around each machine clear of obstructions.
Stack new and finished timber on pallets.
Keep the floor areas level and in good repair.
Check that floors, especially where operators stand, have not become slippery.
Put waste into bins which are cleared away when full.
Keep chip and sawdust extraction systems working effectively.
Mark gangways and fire exits clearly and keep them clear.
Where trailing cables are in use, make sure that they do not create a safety
Revised Jan 2003