On Feb 18, 11:02*pm, GeoLane at PTD dot NET GeoLane at PTD dot NET
wrote:
A continuation of my query regarding slot milling with a 1/8" end
mill.

The peripheral feed per tooth recommended was 0.0005" for a 1/8" end
mill.

What's the feed per tooth for 3/16 *to 1/2" end mills? *Is there any
rule of thumb?

Second question. *With a center cutting end mill, what's the down feed
rate? *BTW, I've got to do this by raising my table - my old BP head
has no downfeed.

RWL

With larger endmills I push it until the machine starts to slow down
or vibrate a little (not hard to do on a Clausing), then back off. I
burned and dulled the first end mill while learning on a Bridgeport,
then I knew when to lighten up. I've never broken an end mill but
other prople have in company shops I ran. The corners chipped off,
good reason to wear eye protection, but in these cases they weren't
injured. I ground the end square past the break, added back relief
almost to the edge, carefully reground the cutting edges (by hand &
eye), and they were back milling again, though not nearly as fast.

The endmill downfeed rate is a lot higher if you drill a starting hole
first. Or you can zig-zag down if the endmill isn't centercutting.

Jim Wilkins