Thread: Saw stop

He has faith in his own creation and you've got to give it to him.

Wow! That's wild.

A great invention, on the surface. Wonder what happens, though, if the blade does not stay in one piece. Could potentially suffer far worse than a lost finger. I think a good, solid cowl is needed around the blade when it's stopped and lowered.

I'd like to see what happens if he runs his hand quickly into the blade. I think it would stop too late to completely avoid injury.

... Steve

Originally Posted by Hermit

Wow! That's wild.

I'd like to see what happens if he runs his hand quickly into the blade. I think it would stop too late to completely avoid injury.

... Steve

True...but any other saw wouldn't stop at all.

Originally Posted by spokeshave

True...but any other saw wouldn't stop at all.

Yep. Better to lose one finger than all of them.

A great invention. The technology could be applied to a range of tools, too, I'd think.

I'd happily pay the extra $$ to have this technology implemented in my equipment. I've never been cut yet, even by a hand-saw, but .....

... Steve

So your saying if the blade does not stop it would only cut 1 finger?

Originally Posted by Wongo

So your saying if the blade does not stop it would only cut 1 finger?

No, you misunderstood. What I meant was that with the device, even moving his hand quickly, it would probably stop before more than one finger was hit.

... Steve

Originally Posted by Hermit

I'd like to see what happens if he runs his hand quickly into the blade. I think it would stop too late to completely avoid injury.

... Steve

The reaction time of Sawstop is supposed to be 1 ms.

This means via simple physics
1 if your hand is dropped under gravity from 0 distance above the saw it will stop by the time your hand has gone 0.0049 mm into the saw, ie a half a hairs width.
2 if your hand is dropped 10 cm above the saw it arrives at the blade doing 1.4 m/s and will stop by the time your hand has gone 1.4 mm into the blade, ie medium cut but leave finger intact.
3 if your hand is dropped 1 m above the saw it will be doing 4.4 m/s and stop by the time your hand has gone 4.4 mm into the blade, leave most of your finger intact.
4 the fastest speeds black belt karate experts generate is about 7 m/s. This means a 7 mm deep cut, even that would possibly not even take you finger off completely.
5 to cut your finger (say 2 cm across) completely off would require a hand speed of 72 km/hr. I guess you could always hang your hand out of a car window and drive past the saw stop?

My guess is that probably case 3 and definitely cases 4 and 5 would break the bones in your finger even if the blade was not moving.

I would like to see all these test confirmed with a pigs trotter.

There looked to be a slight graze on the sausage in the video, but nothing more, at a 'normal' cutting speed..

... Steve

Originally Posted by Hermit

No, you misunderstood. What I meant was that with the device, even moving his hand quickly, it would probably stop before more than one finger was hit.

... Steve

Your guess, at least in theory, is correct

You know, I can envisage a time in the not-too-distant future when something like this would be a legally required safety feature of some power tools.

It's pretty amazing that they can mechanically move that big 'brake' contraption that far in 1 mS. Pretty quick. Even an average relay takes about 10mS to trip.

... Steve

I wonder what it breaks/destroys when activated, and how much it cost to set the saw up again?

Also, what would a bead of sweat from one's brow do to it?

This has been around in the US for some years. he first offered the technology to existing manufacturers with no takers then decided to manufacture a line of saws himself. He has done a LOT of political lobbying to the extent that serious consideration is being given to making the technology mandatory for all saws in the US. This man is on a mission and he is not going to stop, almost it seems as payback for no one picking up his ideas when they were first offered. I think there was a online petition not so long back IIRC concerning the proposed compulsory use of the technology.

Originally Posted by Mini

This has been around in the US for some years. he first offered the technology to existing manufacturers with no takers then decided to manufacture a line of saws himself. He has done a LOT of political lobbying to the extent that serious consideration is being given to making the technology mandatory for all saws in the US. This man is on a mission and he is not going to stop, almost it seems as payback for no one picking up his ideas when they were first offered. I think there was a online petition not so long back IIRC concerning the proposed compulsory use of the technology.

Very interesting. It's not unusual for manufacturers to avoid safety features due to cost. This would make a saw much more expensive.

Just had a thought - does human hair conduct electricity? Something as simple as a fallen hair could trigger the brake, or Poit's bead of sweat possibly, if it got across from the blade to the benchtop.

Also, I wonder if it could be incorporated in a manner that doesn't destroy everything. Does the braking have to be applied directly to the blade like that?

... Steve

There are old threads on the saw stop here on the forum. At on stage the Aussie distributer was around here (maybe still is?) and answered a lot of questions about cost of resetting after a trip, whether green timber, sweat etc would trigger it etc. I think from memory one thing was that if you could prove it triggered erroneously then the replacement parts were at lower cost or free but I might have got that wrong. Worth looking up the old threads anyway.