Riving Knives in America...

[Steve Maskery]

Agreed, Stuart, but using the saw without the crown guard is not the same as using the saw without any guard at all, would you not agree?

There is always a way to guard the saw.
S

 

[ondablade]

I've been banging away on the problems created by the dogmatic way so called safety is imposed on others in another thread.

Wouldn't it be much more constructive if people instead of making tutting, 'in the know' and similarly non-specific sorts of noises about what the other is doing wrong instead simply explained their alternative and hopefully safer solutions?????

That way others can (as they will anyway) agree or disagree, take it or leave it - but at least the word would get out and there might even be some sort of information based debate...

 

[SBJ]

My point is that as an experienced woodworker, I would be comfortable working without ANY guards if I thought the task warranted it. Understanding wood and machinery isn't necessarily a pre-requisite for an operator hence the need for HSE.


I would also always use a riving knife.

 

[davcefai]

Dilemma.

The riving knife on my saw (like, I believe most others) is taller than the blade, to support the guard. moreover it has a little, permanently attached, stub axle for the guard to pivot on.

This means that I cannot use a sled or a tenon jig with the knife and guard in place. Nor can I cut slots.

To remove the knife involves undoing 8 screws to remove the insert, then loosening 2 bolts to release the riving knife. After this I need to screw the insert down again. Then I need to reverse the procedure after making the cut.

The guard is also very intrusive and makes using the saw difficult.

I finally compromised by trimming the knife so that it now stays on permanently. Hell is paved with good intentions so one day I'll get around to building a better guard which will not be attached to the riving knife.

Incidentally while the knife does end up below the blade at the shallowest settings these would be "thin plywood" settings so that there is no risk of pinching.

 

[tomatwark]

When I say some of the HSE rules are daft, I was speaking about the HSE culture we seem to ended up with, partly due to being in Europe. ( This is really another topic for elsewhere and maybe someone wants to get the ball rolling)

The main one which really annoys me is the 10 second stopping rule, to retro fit older machines can cost upwards of £500 per machine, it was this rule that made me decide to not to replace the lad I had working for me in the late nineties as it was going to cost me about £5000 to conform, where as working on my own I did not need to bother.

If built into the cost of new machines fine and also for certain machines such as saw benches and tenoners fair enough but while I now do conform due to gradually up grading my machines over the years, I still think it was a step to far.

I was always taught to check the machine had stopped and isolate before doing anything.

This thread seems to be going off topic but I still would never use a saw without a riving knife and if cutting shoulders without a tenoner would use a radial arm saw before even considering doing it on a saw bench. ( I am lucky enough to own a tenoner )

Tom

 

[Finial]

Thanks Tom. At least someone can be specific! I take your point about the cost of the stopping time regulation. Like most safety regulations, it applied to you as a self employed person whether or not you had employees, though enforcement against a one man band would possibly have been much less likely. There was a quite long lead in time allowed so that businesses could either retrofit or modernise as you did in the end.

The trouble with expecting employees to wait for the machine to stop is that mistakes happen, specially in a busy shop where the machine running down may be hard to hear. And it seems unsatisfactory to have to wait until you can see the teeth to know there is no danger. Working by yourself it may be easier to know the machine has stopped, and you may have had good work habits trained into you. Not all employers do train their employees, so it is inherently safer to have short run down times. Similar to guarding really, an experienced worker may get away with taking guards off for quite a long time, but sooner or later will have a moment of carelessness and get caught.

 

[heimlaga]

Not all of us can afford all machines we want.

I have neither a bandsaw nor a spindle moulder. That is why I regularly cut rebates and grooves on the table saw. The only other way to cut through thick stuff would be the old pit saw blade that lies in the shed......

My cheap cure for the safety problem is a home made top guard which is rigid enough to prevent a board from beeing thrown upwards by the blade. The riving knife is of cause low enough so that it can be used all the time.

 

[Setch]

The problem with visually checking the blade is that the strobe effect caused by fluorescent lights can make the blade appear stationary when it's still turning. A massive amount of tablesaw accidents are caused by contact with the blade after it has been powered down, usually whilst reaching in to remove the worpiece or clear away waste.

I have an old Elu flip-over site saw, and it takes *ages* to spin down - I usually manually brake it with the end of my push stick if in doubt.

That said, if it's properly guarded and you're following the other general workshop safety rules it makes not difference whether it's spinning or not.

 

[Deansocial]

i recently used an old RAS and ou could do 3 more cross cuts in 3x2 after switching it off it took that long

 

[Finial]

The problem with visually checking the blade is that the strobe effect caused by fluorescent lights can make the blade appear stationary when it's still turning.

Yes, so they say, though I have never seen this effect in my workshop. Mind you, with my eyes it's not easy to see the teeth clearly anytime.

A massive amount of tablesaw accidents are caused by contact with the blade after it has been powered down, usually whilst reaching in to remove the worpiece or clear away waste.

I'm sure that is right. That was presumably why the regulation was introduced.

 

[Finial]

i recently used an old RAS and ou could do 3 more cross cuts in 3x2 after switching it off it took that long

If it is still in use for business purposes perhaps you ought to let the authorities know!

 

[Chems]

Incidentally while the knife does end up below the blade at the shallowest settings these would be "thin plywood" settings so that there is no risk of pinching.

A comment like that shows why people should read up a little more before using saws. The RK is not only there for pinching but also to aid in not allowing the wood to pivot on the blade causing the most spectacular kick back and also to protect the back of the blade from offcuts. If your RK disappears at the shallowest settings then its not set right and you should spend a bit of time tweaking it.

 

[Deansocial]

i recently used an old RAS and ou could do 3 more cross cuts in 3x2 after switching it off it took that long

If it is still in use for business purposes perhaps you ought to let the authorities know!

its in a small workshop with 1 guy working there, he is 78-9 years of age i don't think he cares that it takes that long to stop and has been in a workshop enviroment long enough to work safely.

 

[davcefai]

Incidentally while the knife does end up below the blade at the shallowest settings these would be "thin plywood" settings so that there is no risk of pinching.

A comment like that shows why people should read up a little more before using saws. The RK is not only there for pinching but also to aid in not allowing the wood to pivot on the blade causing the most spectacular kick back and also to protect the back of the blade from offcuts. If your RK disappears at the shallowest settings then its not set right and you should spend a bit of time tweaking it.

To a degree, you're right. However the geometry of the saw does not permit the RK to be visible at the shallowest settings. The blade does not rise vertically but rotates around a pivot. (At least on my Ferm Z250 it does). This means that if,at the lowest setting, the RK is level with the top of the blade, at higher settings it will be higher than the blade so that I cannot cut rebates or tenons.

My RK knife surgery gave me what I consider to be the best compromise. In practice the Riving Knife starts to appear when the blade is at 8mm (tip of highest tooth) I would normally have it higher, even when cutting 3mm plywood so that I can always have some riving knife effect.

And by the way, I read more than a little before setting wood to tablesaw. Essentially I arrived at a compromise where I could be as safe as practicable and still retain a usable tool. H&S regulations, if followed blindly, could bring most activities to a stop - people could well die of boredom trying to conform. The nanny state can, and often does, go too far.

 

[dickm]

The problem with visually checking the blade is that the strobe effect caused by fluorescent lights can make the blade appear stationary when it's still turning. A massive amount of tablesaw accidents are caused by contact with the blade after it has been powered down, usually whilst reaching in to remove the worpiece or clear away waste.

Certainly don't want to downplay the dangers of not seeing that a blade is still rotating, but I really don't believe that strobe effects can be blamed in anything other than exceptional circumstances. To get a strobe effect, the teeth have to be illuminated almost exclusively by electric light, and move an exact integer number of positions in 1/50th of a second (or 1/60th in the USA). If the blade is slowing down anyway, each time the blade speed is near a strobe speed, the first effect will be teeth appearing to move slowly forwards, be stationary for a tiny amount of time, and then move backwards (remember the wheels on wagons in old westerns?)
So there might be something less than a second when the blade appears to be stationary. Of course, if the no load speed of the blade just happens to be such that it is exactly the strobe speed, then the blade will appear permanently stationary, but the chances of that are pretty small.
Sadly, accidents are usually the result of humans taking a chance, not a feature of the machine.

 

[Steve Maskery]

THe only accident I have ever had with a TS was cutting some thin ply. The riving knife was either absent or below the table, I forget which. I hadn't had the saw very long, I was very inexperienced and didn't know what I was doing. I learned what kickback was, the hard way. The board hit me edge on, it was like a knife.. I had a lump on my arm like a Tom & Jerry cartoon and I still have the scar, 20 years later. It made me sick.

I'm rather glad it happened, actually, in the sense that as a result I've never needed persuading of the importance of RKs and guards.

Just because the wood is thin it doesn't mean it's lower risk.

S

 

[misterfish]

It can be interesting (as well as sphincter-puckering at times) watching US woodworking and building shows. One episode of Hometime a year or so ago was the worst - ripping thin and odd shaped mouldings to less than an inch width just using fingers with no guard, splitter or riving knife.

I've just watched This Old House where pieces were cut with no guards etc and with fingers close to the blade. They (Norm and Tom Silva) then cut a 3/4 inch wide dado along the whole length of a 16 ft plank - this was using a good quality site saw. You could see they were being very careful (and obviously have decades of experience between them) but it was not comfortable to watch.

In total contrast was the new Rough Cut series. He uses a splitter behind the blade and a proper overhead SUVA guard to allow safe dado cutting. He also emphasised that push sticks should be used when the distance between the fence and blade is less than a lage hand span. So it seems that a variety of working methods are used!

Misterfish

 

[Chems]

Just because the wood is thin it doesn't mean it's lower risk.

Even more reason, more likely to have a puncture type wound than a blunt blow with a thin piece.

 

[tomatwark]

I think with most modern fluorescent lights the strobe effect has been solved, I know that when they where intorduced it was a problem because of the rate they flicker at but I though that had been sorted decades ago.

Tom

 

[jetsetwilly]

Rise up, ye undead thread

Just wanted to say that in all this talk of nasty unsafe american saws, nobody has mentioned nasty unsafe european fore-and-aft fences. My sip 01332 is a nice enough saw (apart from the bendy tables, arbour run-out, wobbly lead screws....) but locking the fence down parallel to the blade is far from easy - the rear claw often bites off-square and shows no inclination to self-correct. Many times I've wished it had a simple T-square fixing instead (or any other front-only fence fixing).