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Reducing RPM

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  • Reducing RPM

    I'm working out the CAM for my next project. Most of the cuts will be roughed with a 3/8" down spiral and then finished with a 3/8" compression bit.

    I did some test last weekend and 13000 rpm at 390 IPM seemed to work really well and gave me a chip load of .015 which is on the low end for the 2 flute, hardwood in the US Router Tool spreadsheet. All good.

    But I have some small, .75", pockets and a 9" gear shape. None of which, I imagine, have runs long enough to actually actually achieve 390 IPM. I'm thinking of ratcheting down the RPM to 12,000 to try and maintain some chip load. Any issues with that? Good idea, bad idea, irrelevant?

    Cobra Elite 408, ATC, 5 hp spindle, vacuum table, 4th axis, Fusion 360
  • #2

    Try it and see. I use chip load as a good starting point then use the RPM slider and speed adjustment in WinCNC until it cuts optimally. I use the sound of the wood to get in thr ballpark on where I think I need to be.

    12k won't hurt your spindle if that's what you're worried about. The fantastic thing about spindles is they have pretty great torque all throughout their RPM range. You'll be fine cutting at whatever speed you want.
    4'x8' Stinger IV w/ 4.2 hp spindle and 4 tool ATC
    Mister system
    Phenolic Vac table
    Hurricane Vac
    Vcarve Pro 10

    Catholic school IT director, wannabe woodworker, Krav Maga instructor, and CNC enthusiast