How to use a circular saw bench safely
Date posted: 20 October 2015
Circular saw benches, also sometimes referred to as rip saws, are used for cutting wood in the direction of the grain. These cause more accidents than any other woodworking machine, often resulting in finger amputations.
It is crucial for employers to undertake a thorough risk assessment before using these machines in the workplace. If there are no alternative means of carrying out the work it should only be undertaken by trained and competent workers – on machines that comply with legal regulations and are well-maintained and suitably guarded.
Here we take a look at the key safety risks associated with the circular saw bench and how accidents can be avoided.
What causes most accidents?
Most accidents are caused by missing or inadequate guards, which allow accidental contact with the blade. These could have been prevented by having a properly-adjusted saw guard in place and using a push-stick to help avoid fingers getting close to the blade.
Alongside the obvious risk of coming into contact with the sharp blade, there is also a risk of being hit by an ejected workpiece ('kickback' of the workpiece), which has caused serious and even fatal accidents.
In all of these scenarios, a lack of training or inadequate training in using the circular saw bench, is often the cause of accidents.
Purchasing a new circular saw bench
If you are buying a brand new machine, remember that it should bear a CE Mark; it should be supplied with a declaration of conformity; and it should be designed and built to meet BS EN 1870–1:2007 + A1:2009. With regards to the blades, these should meet BS EN 847–1:2005.
General safety considerations
Undertake a risk assessment:
A thorough risk assessment is vital, incorporating all potential uses for and operations at the circular saw bench. This process should identify all actions necessary to eliminate or control risks. A part of the risk assessment should involve considering whether there may be a more suitable woodworking machine for the tasks being undertaken, e.g. a guarded vertical spindle moulder / router would be more suitable for grooving work.
Fit the machine with a riving knife and saw guard:
These machines should be fitted with proper top guards and riving knives which require careful adjustment for each job undertaken – to within 8mm of the blade. These act as a back guard and prevent the wood from closing up onto the blade and being ejected. The riving knife needs to be thicker than the plate of the saw, but thinner than the kerf (i.e. the thickness of the cut). You may need to have access to a selection of riving knifes if different saw blades are being used.
Machines must be entirely enclosed beneath the table.
The take off table must extend so that the distance between the saw blade spindle and the rear edge of the table is at least 1200 mm – or longer if the operator is tall, in order to limit the risk of any contact with the blade when taking cut pieces off the table.
Provide an effective braking system:
To limit the risk of contact with the saw blade during run down, these machines need to be fitted with a braking device capable of bringing the blade to rest in 10 seconds or less.
Any circular saw benches with a rundown time greater than 10 seconds should have been fitted with a braking device by 5 December 2003, unless they were already fitted with a manual or foot-operated brake instead.
Keep saw blades in good condition and set properly:
If the machine's blades are dull, poorly set or badly ground they require more feeding effort on the part of the operator, creating a greater risk of workpiece kickback accidents (and also achieving lower quality work).
Wood resin / gum sometimes build up near the saw's teeth and this can cause the saw to stall or the wood to stick. If the blade needs cleaning always stop the saw first, remove the blade, and use an appropriate scraper to get rid of the resin / gum.
Use only safe saw blade diameters:
On the machine there should be a mark to indicate the diameter of the smallest saw blade that is safe to use due to kickback risks.
This is because a small blade – with a diameter that is less than 60% of the diameter of the largest blade the saw can take – will have a low peripheral blade speed, will not cut efficiently, and will create a higher risk of kickback.
Control airborne wood dust:
Wood dust poses a serious health hazard and therefore to control airborne dust saw benches should be fitted with effective local exhaust ventilation (LEV), both above and below the table.
Adequately supporting the workpiece
Proper workpiece support is vital whenever you are using a circular saw bench.
Use extension tables or roller supports at both the infeed and outfeed ends to adequately support large workpieces. As covered briefly under 'Riving knife and saw guard', if the task demands a second operator at the outfeed end to remove finished pieces, extend the table to create a distance of at least 1200mm between the saw blade spindle and the rear edge of the table to help avoid contact with the blade. This second operator must stay at the outfeed end of the extension at all times, never reaching forward towards the saw to take cut pieces. While the riving knife reduces the risk of contact, it can't entirely prevent it.
Use a rip fence / cross-cut fence to provide workpiece support during cutting. To help prevent workpiece kickback, the front of the fence needs to be set no further than the base of the saw blade gullet at table level. If you need to cut shallow / angled work, you may need to replace the normal fence with a low fence to help the use of a push-stick and to prevent the canted saw blade touching the fence.
Proper use of the push-stick
To prevent finger / hand injury, always use a push-stick when you are making cuts less than 300mm in length, or whilst you are feeding in the final 300mm of a longer cut. Use a push-stick that is a minimum of 450mm long, and features a ‘bird’s mouth’ design at the far end.
Remember to keep the leading hand as far from the front of the saw as possible, and ensure hands are never in line with the saw blade. Always use the push-stick to remove the cut piece from between the saw blade and fence unless its width is greater than 150mm.
Use of a demountable power feed
If it is practicable, use a demountable power feed to further lower the risk of contact with the saw's blade. This unit is not a replacement for a riving knife, however, which should still remain in place whenever a demountable power feed is being used.
Ripping and cross-cutting
To carry out safe ripping and cross-cutting you need to focus on:
- providing adequate support for the workpiece
- using a push-stick properly
- positioning your hands safely
- adjusting the riving knife and saw guard properly
Riving knives need to:
- be rigid, and set carefully so they are in line with the saw
- feature a chamfered leading edge and be shaped so the inside edge follows the contours or the largest saw blade as closely as possible
- be thicker than the body of the saw blade, but a little bit thinner than the width of the cut
Saw guards need to be:
- easy to adjust, and adjusted as close as possible to the workpiece's surface
- large enough to properly enclose as much of the blade as is practically possible during cutting
Saw blades must be:
- set to ensure the teeth project through the workpiece surface during cutting, but no higher than necessary
- suitable for the particular work being carried out (for example, if you are cross-cutting the ripping blade must be replaced with either a cross-cut or combination blade)
Rebating and grooving
Do not use a circular saw bench for cutting a rebate or groove unless the blade is guarded with a suitable alternative guard / fixture – because it will not be possible to use the normal saw guard. The Health and Safety Executive (HSE) says that if practicable, the tunnel created by the pressure pads should be designed to meet the requirements of BS EN ISO 13857:2008. The HSE also warns that stopped grooving should not be carried out on a circular sawing machine, instead you should use a vertical spindle moulding machine or a hand/pin routing machine.
Angled cutting and bevelling
The HSE also advises that angled cuts can be made on a tilting arbour saw by inclining the saw blade to the desired angle and feeding the workpiece as for ripping or cross-cutting. They say, "The saw guard must be suitable for this operation and be designed so that it prevents the risk of contact with the inclined blade. The fence should be set in its low position or an auxiliary fence used to prevent the possibility of the fence touching the rotating saw blade." When using machines featuring a fixed-position spindle, you may have to build a basic jig in order to offer enough workpiece support during the cutting job.
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