Russell"
> >> I posited an upper feed rate of about 1 m/s or 1 mm/ms.

Oli:
> > I was wondering about these calculations. I don't know much about
> > table saw terminology but I assume you mean the blade edge travels 1
> > metre per second or 1mm per millisecond?

Olin:
> No, feed rate refers to how fast the workpiece is moved with respect to t=
he
> machine. =A0In this case that would be how fast the wood and finger appro=
ach
> the blade. =A01 m/s is a really really high feed rate for a hand fed table
> saw. =A0That would be quite reckless even if the saw could digest the wood
> that fast. =A0I think Russell was trying to come up with a very pessimist=
ic
> upper bound. =A0I'd say typical feed rates are a few mm per second to a f=
ew
> inches per second, certainly not 10s of inches per second, at least for a
> home table saw the average basement woodworker will have.

Yes - I was referring to the rate that the finger may approach the saw at.
As Olin notes, 1 m/s is quite fast - certainly faster than you feed
anything except maybe light  wood with a firewood saw.
This sets an upper bound at which the mechanism needs to react at to
deal with almost any sensible situation.

With a 1m/s pop back rate you could ALMOST swing your hand against the
blade and have a reasonable chance of it saving you.
If you did this capacitively you *may* be able to trip it prior to contact.

I did post  some calculations re saw blade rotation and number of teeth etc.
I used 1200 RPM as a multiple of 60 seconds/minute and then noted that
you could scale this up as required.

Similar results to what Oli provided.

The "pop back" method seems liable to be workable - especially so if
you interpose a shield where the blade was so you don't have to go
back far or keep going back.


          Russell

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