Oli Glaser wrote:
>> I posited an upper feed rate of about 1 m/s or 1 mm/ms.
>
> 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?

No, feed rate refers to how fast the workpiece is moved with respect to the
machine.  In this case that would be how fast the wood and finger approach
the blade.  1 m/s is a really really high feed rate for a hand fed table
saw.  That would be quite reckless even if the saw could digest the wood
that fast.  I think Russell was trying to come up with a very pessimistic
upper bound.  I'd say typical feed rates are a few mm per second to a few
inches per second, certainly not 10s of inches per second, at least for a
home table saw the average basement woodworker will have.

A local lumber mill has some impressive circular saws that slice up whole
logs.  The feed rate might actually be around 1 m/s for those, but this is a
large industrial machine, the logs are automatically fed, and no human is
within 10 feet of the blades when they are cutting.

> The reason I ask is that in the video it says the blade is travelling
> at 5000RPM. By my calculations (which may be way out)
> assuming a blade of 10in diameter = 31.4in circumference = 797mm. At
> 5000RPM that's 83.3 turns per second which is 83.3 * 0.797 =
> 66.38m/s. So roughly
> 6.6cm in 1ms or about 30 degrees. Am I missing something here? is a
> standard blade far smaller in diameter than 10in?

No, that's about right.

> With those calculations it seems the saw would have to stop quite a
> bit quicker than 1ms to avoid damage to finger.

To avoid any damage, yes.  But the feed rate also matters.  Even if the saw
completely removes 1mm depth of flesh for the width of the blade, it's going
to hurt but your finger will heal and be OK.


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