Pete C. wrote:
Ignoramus17758 wrote:

I am trying to make a dog clutch that mates with the knee crank and
replaces the crank handle:

http://igor.chudov.com/projects/Brid...-8057.jpg.html

I wrote a G code program that makes such a clutch from a flat block of
metal, with a 1/8" end mill.

In machinable wax, it does a great job, zips through it, and makes a
surface that mates with the crank handle perfectly, I was very
impressed.

In steel, however, this little 1/8" endmill works for a while, then
breaks after 1/2 hour.

1/8" end mill
4 flute
1 IPM feedrate
2,000 RPM
plenty of coolant
unknown steel, but feels like 1018.

What depth of cut are you using? What is your chip load per tooth? What
is your cutter SFM?

You should never use an end mill smaller than you need, and from memory,
the knee crank "crown" could be milled with at least a 1/4" end mill
which will be stronger, have a higher SFM at your spindle speed and have
more chip clearance.

So, say I'm making a rectangular hole. Would I cut it with, say, a 1/4"
side mill, and finish up with a broach?

Thanks,
Rich