I have a 2 1/2" diameter fingernail bit. I only wanted to use the top part
of it, which is only about 1" diameter. I figured that full speed would be
okay, and it seemed to work out; but I wonder if the speed is for the bit,
or the part of the bit I actually used?

Toller wrote:

I have a 2 1/2" diameter fingernail bit. I only wanted to use the
top part
of it, which is only about 1" diameter. I figured that full speed
would be
okay, and it seemed to work out; but I wonder if the speed is for the
bit,
or the part of the bit I actually used?

There is no free lunch.

The centripetal forces are applied to the entire bit, with the max force
at the largest radii, not just the part that is cutting.

Consider yourself lucky that the bit was probably conservatively rated.

I would not suggest going there again.

Lew

On Sun, 11 Feb 2007 22:40:50 GMT, "Toller" wrote:

I have a 2 1/2" diameter fingernail bit. I only wanted to use the top part
of it, which is only about 1" diameter. I figured that full speed would be
okay, and it seemed to work out; but I wonder if the speed is for the bit,
or the part of the bit I actually used?

It's both. You shouldn't ever exceed the maximum recommended speed of
the bit (which you may not actually be given my the manufacturer
unless you contact them), but the best speed to run the bit within
that range may not be the same whether you are using all or part of
the bit.

When in doubt, spin it slower.


-Leuf

http://www.newwoodworker.com/ref/rtrbtspds.html

Toller wrote:

I have a 2 1/2" diameter fingernail bit. I only wanted to use the top part
of it, which is only about 1" diameter. I figured that full speed would be
okay, and it seemed to work out; but I wonder if the speed is for the bit,
or the part of the bit I actually used?