wrote in message
...
On Sat, 22 Oct 2016 15:14:28 -0700, "Bob La Londe"
wrote:

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.





Greetings Bob,
My screwless vises are hardened steel. Pretty damned hard but not
quite as hard as a file. So, I would advise using carbide cutters. Try
60 SFPM to start. That's only 916 RPM for a .250 dia. cutter. It may
be your high speed spindle is just plain too speedy. Even a .125
cutter at 160 SFPM, which is probably too fast, works out to 4885 RPM.
So try a .125 cutter at 7000 RPM and see how long it lasts. Your vise
may not be as hard as mine.
Eric

They are pretty darn hard. I roughed off as much as I dared on the big
mill. For what I want I need to finish in place. Fortunately I have a
little mounting slop with my hold downs so I can push the vise front to back
a little to minimize what I need to remove. I'll indicate the lower uncut
face of course to minimize other issues with geometry, but the final top
step needs to be cut to alignment and flat to travel after the vise is
bolted down.