breaking bits

I am trying to cut 12mm birch plywood for the milled/printed 3d printer, but I keep breaking bits. I have lost 2 Freud 75-100:

DW660 with variable speed controller, running at ~ 18k rpm. 2mm depth of pass with a 10mm/s feedrate. MPNC has been working great cutting MDF and pine. I re-surfaced spoil board and verified that the overall squareness of the machine.

Any suggestions on what could be going wrong?



Do you notice anything else besides the bit breaking?

Those bits are quite pricey. But I have not broken a bit with 18mm BB and gone closer to 6mm DOC and 10mm/s. I use the ones from Ryan’s shop. I have dulled the bits. IIRC, the only time I broke a bit was with a deep straight plunge.

You should have no problem with those numbers. I would start looking for a missing bolt or something, loose pulley. Is it always plunging or anything when it breaks?

Thank you for the input.

Both bits broke on X-Y move, not plunging. I was cutting the back (for MP3DP), all 8 holes were drilled perfectly, they broke during outside tool path (not at the point where depth was increasing). There seemed to be some excessive x-y wobble if I tried to wiggled the middle assembly. So I decided it was best to disassemble and verify everything. The only bolts loose were the tension bolts (as they should be). I suspect everything will be fine when I get it back together.

The MPCNC is in the garage … there is no telling if a basketball, lacrosse stick or something else decided to land on it. The kids don’t seem to respect the machine the way I do :frowning:

I agree the Freud’s are pricy … they stock them at local Woodcraft. I just ordered bits from Ryan’s shop, certainly not sure why I hadn’t.

Good thing it is Mostly Printed!

Still a bummer, hard to know for sure without seeing the issue.