Quote:
Originally Posted by DampRobot
Yes, 6 IMP. We do throw a good chip though, nice little curls. It is quite slow, mostly because we have a mill mentor who is, shall we say, conservative, with his machine's speed. He is right to go slow, though, the chips look good and we have had problems with breaking tools in the past (and crashing into clamps, but that's another story).
I'm sure with those router speeds, you'll be able to go faster. We're running a very different type of mill (a HAAS toolroom mill), so take my cutting speed experience with a grain of salt.
Perhaps we do cut too slow, but since the chip looks good and our part tends to vibrate excessively if we push it much faster, I'm inclined to stick with what we have now.
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Are you using carbide or HSS? With HSS I could see 6 IPM being reasonable, but you should be running at about 0.003 IPT or more with a good carbide end mill, which would be a baseline of double what you're currently running. With a cutter that small and a top speed of 3600 RPM I would never run slower than max speed. We were forced to run our machine no faster than 2500 RPM recently and were slotting 1/4" plate at 23 IPM with a 3 flute end mill. You have a less rigid machine, but 1/4" Al plate isn't very taxing and I would expect similar performance.
As Scott mentioned, with a chip load of 0.0015 IPT you're coming closer to smearing material off as opposed to shearing, which will dull your tool and cause premature breakage. This will be a bigger problem if you're conventional instead of climb milling as chip formation begins with zero thickness and increased rubbing.
If you find that you're breaking tools it's almost certainly a chip evacuation problem. We can slot 1/4" plate with a 3 flute aluminum specific end mill indefinitely as long as the chips are cleared out of the path of the tool. As soon as you start re-cutting chips you run the risk of dulling/snapping the tool or welding the chips to the flutes.