Hi dgoddard,
For feeds that slow I have to assume one or more of the following:
1) the machine is fragile
2) the endmills are very small
3) your tooling is HSS not carbide
4) the steel is pre-hardened.
If some of these are true, then your feedrates make sense.
We run 1/8 endmills in 4140 (tool steel) at 12 ipm. That's a standard carbide endmill. If you use "extreme" endmills (high helix) you can run some pretty crazy feed rates. We use them occasionally for slotting steel, and with the proper type of path (like a trochoidal path for example) you can cut with a depth of cut equal to the Ø of the cutter at well over 100 ipm. Of course that's more like Ø3/8 endmills, not Ø1/8.
Anyway, have you ever thought of programming in metric? With metric feedrates you have way more versatility. For example, 2 ipm would be approximately 50mm/min. 2.7 ipm would be about 68mm/min. No decimals required. We have always used metric since all our customers (the automotive companies mainly, even the US ones) work in metric. Like the metric system in general, it's way easier than the imperial system.
Just a thought.
Dan
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(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
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