Joe Barta wrote:

For the WTF file...

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From: http://www.mass.gov/dph/bhsre/ohsp/f...ts/facev21.htm

Woodworker Dies When Struck by Tool Knife Launched from Overarm Router

A 32-year-old woodworker was fatally injured at work when a steel tool
knife was propelled from a rosette cutter. The cutter was installed in
an overarm router. The steel tool knife penetrated a polyacrylic sheet
(trade name--Plexiglass) shield and then penetrated and exited his
chest, sub-sequently ricocheting off the wall before finally landing.
The victim was an experienced wood-worker, whose job also included
tool grinding and setup of spindle moulders.

The knife, measuring approximately 1-5/8 inch square, was part of a
cutter head assembly which had been previously used on a drill press
at much lower cutting speeds. It was custom designed and built for the
drill press, not for the router which is run at much higher speeds. At
the time of the incident, the router was set for 20,000 rpm and was
being used to make custom rosettes. The maximum permissible speed was
not indicated on the cutter head, and there were no written procedures
for its use (e.g., the recommended cutting tool speed). The knife was
held in the 4-3/4" diameter cutter head by flat shims and set screws.
The set screws could not counteract the centrifugal forces generated
by the high-speed rotation.
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Now, for ****s and giggles I made the following calculations. I was
wondering, using the router speed and cutter diameter, what might have
been the speed of that cutter as it sailed towards it's non-thinking
victim. (Granted, I'm sure there are more complex mathematics required
to calculate this accurately... but this is good enough for my
amusement ;-)

20000 rpm
4.75" dia bit

bit circumferance = 4.75 * pi = 14.92"

20000 rpm/60 = 333.33 rounds per second

333.33 * 14.92" = 4974.19 inches per second

4974.19 /12 = 414.52 feet per second

414.52 * 60 = 24870.94 feet per minute

24870.94 * 60 = 1492256.51 feet per hour

1492256.51 / 5280 = 282.6 miles per hour

So, according my amateur calculations, that cutter blew through his
chest at 283 MPH!

Moral of the story? Well.... if you have to ask ;-)
20,000 for a rosette cutter sounds like a recipe for disaster, which
coincidentally, it was! I don't have a rosette cutter (yet--thinking of
getting one soon), but I'd envision cutting at the slow speeds that a
Forstner bit requires. Am I wrong?

Just looked it up. 350RPM is recommended speed. sounds perfect to me.

Dave