[tlmkr38]

In a couple of days I've got to mill some slots in mild steel ( cold roll ) . Since we normally use our cnc to drill holes in production parts we haven't actually used it enough to get an idea on what feeds and speeds to use milling yet. I've done manual milling for 27 years but this is new to me.

What I have is a .250" slot 1.25" long and .400" deep. I plan on drilling the ends so I won't have to plunge with the mill. Thinking of roughing with a .187 mill then take a finish cut with a .250. I have 71 of these to cut and possibly another 71 the same but 2.00" long. I think using carbide would be best for wear but not sure about what speed, rpm, and DOC to use. Our machine is limited to 4500 RPM and has coolant on it, no air blast. I was thinking 2500 RPM 0.050 DOC and 10 IPM. does this sound close? I want to run it fast but don't care to break a bunch of mills..

Any ideas are appreciated as this is all a learning curve for me

The mill is a Fryer tool room mill but this is the only board I could think of to post this one... I'm new on here also ..

[rustyolddo]

First, I'd suggest getting a copy of G-Wizard, it makes it easy to find the optimum feeds/speeds. It takes into account tool deflection, something not often calculated, It will optimize your cut so that you can get the max metal removal without trashing tools. It's handier than a pocket on a shirt.

GWizard: A CNC Machinist's Calculator

Assuming a 1/4" 4 flute carbide, uncoated EM G-Wizard comes up with 3530 RPM, 18 IPM, 0.070" DOC. That's with 1" tool stick out, full slotting. If you plunge with the EM, make sure it's a center cutting type and cut the feed rate by half for plunging.

If you run a 3/16" 4FL carbide EM with 1" stick out, 4780 RPM, 15 IPM, 0.040" DOC Max, that's on the edge of too much deflection. If you go 3/16", leave about .010" for a finish pass and drop the feed rate, climb mill.