On Thu, 13 Jan 2005 21:24:27 -0500, "Ted Clark"
wrote:

Hoping some people can give me their input on this:

I have always made keyseats in shafts by cutting the entire depth in one
pass using the correct diameter slot drill for the keyseat. For example: I
would use a 1/2" diameter slot drill for a 1/2" keyseat, touch the top of
the shaft with the slot drill, raise the table until the slot drill cut its
full diameter on the shaft and then go another 1/4" deep. This has always
worked for me in the past.

The foreman of the facility where I work said this was incorrect. He said
what I should have done was go in with a smaller cutter first, such as
7/16", and then finish with the 1/2" slot drill.

I will assume that what you mean by "slot drill" is an end mill. I
can also assume you ended up with an oversize keyway?

After all, slot drills are made to a minus tolerance. I believe by taking
two cuts, you run the risk of creating an oversize keyseat.

When new, they are generally on size, neither over or under within a
pretty tight tolerance.

Just wanted to know what other people's thoughts were.

My thoughts are that he's wrong too. If I want, or need, a tight
fitting keyway, I'll do it with a smaller cutter, but instead of using
an "on size" cutter for the next cut, I move over to each side,
slightly less than half the difference between the size I want and the
cutter I have, then nibble the last thousandths out until the gage
blocks just barely squeeze in. End mills can, and do, walk, and it's
too easy for one to go oversize. "You can always take another cut,
but that putting on tool is a bitch to grind."

Greybeard.