I've got some pretty specific needs for some of my machining. To that end I
was modifying a screwless vise today to allow me to take advantage of the
full working envelope of one of my smaller machines. I started out just
using Mach 3 wizards and seting it for "hard" steel. Snapped a 1/2" end
mill like a small stick. So I picked up a roughing mill and ran nearly the
same feeds. It did it, but I was getting a red hot curl instead of just
chips. I backed off the feed and still got mostly chips, but I still got a
blue curl pushing ahead of the mill. Then I decided I better pull out
something better for speed and feed calculation. FS Wizard Lite on my
phone. I plugged in 4140 as the material figuring it was a good starting
point and it told me slower RPM and slower feed rate for about the same chip
load. I got about 90% nice blue chips (no red glow) and 5-8% silver chips,
and still had a small bue curl pushing ahead of the roughing mill. The cut
itself looks pretty darn good for using a roughing mill. I did have to take
the burrs off with a file and some rather heavy pressure. A deburring tool
wouldn't touch the bigger ones at all.

Now I need to move the vise to the small high speed machine and finish cut
in place. Its only a 2HP spindle, and its high speed (24K) so picking the
right metal to plan the feeds to get that nice cut to alignment finish (with
a smaller mill no less) may be kind of important. Its got no torque at all
below 6K, and at 6K it doesn't have much.