This is a topic I wanted to cover as part of the Safety Week 08 as a video, but I don’t have a good enough range of devices yet to really do the topic justice. So I’ll write a bit about it instead!
What I’m talking about here are on-tool safety devices, and onces that we use to improve our material handling (primarily keeping things we want to keep away from the cutters!)
There are a whole raft of devices: push sticks, holddowns, featherboards, splitters, riving knives, guards, anti-kickback pawls etc and so the list goes on.
There are two primary things all these safety devices are trying to achieve: keeping your bodyparts away from the cutting things and/or stopping the cutting thing throwing the material at you at very high speed.
Before I go on, there are some rules. (In fact it seems many of the rules and instructions provided with machines can be generalised into stopping the tool biting you, or incorrectly eating the material it is being fed. I guess the code violation of reading the instruction manual may have to be overlooked if you want to be safe!)
The rules are: no loose clothing, hair tied back (unless your haircuts are as short as mine!!), no jewelery, no rings, no gloves. There are lots of don’ts. If you look at the list, it can also be generalised. Don’t provide the machine anything that it can snag on and pull you into it. It happens a lot – don’t become a statistic.
The first category of devices are ones designed to stop you getting cut. These include pushsticks, machinery guards and techniques. The first two are obvious – keeping your hands away from the cutters so you can manipulate the workpiece from a distance, and blocks so if you do stray too close there is something there to impede you from getting to the cutter.
Techniques though? Perhaps not the best term, but I’ll explain what I mean. There are a number of things you can do to reduce the likelihood of an accident occurring. Keep the blades sharp (????!!!!!), keep the machine lubricated, especially the contact surface between the machine and the material, operate the machine at sufficient speed, don’t over-tighten the material holddowns (ie so they are not pushing too tightly onto the work). All these will achieve one thing – preventing you from being tempted into applying too much pressure when feeding the material into the tool. The more you push, the more likely you are to slip, and fall into the blade. On the other hand, the easier a piece of wood slides nicely into the tool and out the other side, the safer it is, the finer the finish, and the more enjoyable the whole woodworking experience. What would you prefer – having to fight to get the material in and through the machine, or have it glide on past?
Back to the other two – guards are obvious. Well, so are pushsticks, but they get avoided so often. I think the reason they are is because of that loss of feeling and control for you as the operator. If you are physically holding the material you can better control where it is going, and how hard it is to get it there. We recognise the need for a pushstick, but are concerned about loosing control of the workpiece. So get a better pushstick! And use some of the anti-kickback devices so the concern does not have to be there in the first place.
The basic pushsticks consist of a handle, and a small notch to push on the work. Sure they do that, but there is nothing stopping the workpiece skewing and getting caught (and thrown). They are also a point-contact, so for example the back of the blade of a tablesaw can start to cause the workpiece to lift (and potentially be thrown again).
As much as they keep the hands clear, they are a poor design. Pity so many of the commercial ones are just this type.
Instead, how about ones that not only feed the work into the device, but also hold the work down on the table?
This (from Taunton’s Fine Woodworking) is just one design, but you get the idea- it pushes from behind and still holds the work down.
Couple this up with some sort of featherboard, and the workpiece is controlled, unlikely to float (what I call it when the rear of the blade lifts the work up – it looks like it is floating on a jet of air), and pushed through with your hands clear of the blade.
You can also have featherboards holding the work down, as well as against the fence, as seen here with the MagSwitch version of a featherboard.
There is no reason why you can’t make your own pushsticks and featherboards – the important thing is to have them, and use them!!
So now we are moving onto stopping the work being thrown. Commonly called a kickback, the tools, such as a tablesaw, can propel your project towards you at speeds approaching 200km/hr. Believe me, they hurt when they hit! Never mind what you were working on is probably wrecked in the process.
There are all sorts of reasons why a kickback occurs, but it all boils down to one thing – instead of cutting, the tool somehow managed to get leverage on the workpiece. It could be that the kerf on the wood closed at the back because of forces inside the wood that were relieved during the cut, causing it to close on the blade, or you slightly skewed the piece so the back of the blade got a good purchase. It could be a misaligned fence, or (such as with a router) you fed the material in the wrong direction.
There are devices to try to prevent these occurring, such as splitters and riving knives, anti-kickback pawls, featherboards and board buddies (a kind of wheeled featherboard, where the wheels can only rotate in one direction)
I’m getting a bit of track here, so let me drag it all back to this:
To be safe during a cut, you want to keep yourself from being machined (to not split hairs here), nor do you want to be hit by self-made missiles.
By using guards, pushsticks and holddowns, combined with correct techniques, your chance of a mishap occurring is greatly reduced.
Filed under: Uncategorized | Tagged: Hazards, Kickback, MagSwitch, Manual Handling, Pushstick, Safety, Safety Week | 2 Comments »