Z plunges scarily in the same place every time. How many ways am I screwing up here?

Maybe a less aggressive depth of cut might help, too. Looks like pretty hard wood. The Carbide3D #201 looks functionally equivalent, for $20 apiece, if you don’t wanna risk another Amana. Might also think about HSS for wood - it does tend to be (or feel) sharper. I paid just over $1 apiece for some 1/4" HSS cutters from “tool-edge” on ebay.

I feel like you could go a lot more aggressive with clamping, too. Getting something over the top of the piece might definitively eliminate that problem (I like some DIY oak clamps of the design that many people use for their first project)

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My guess is also that the collet was not tight enough. On my Carbide Compact Router, it seems like I need to tighten the collet more than I do on my other machine that has a DeWalt router, at least for 1/4" cutters. I’m using the precision 1/4" collet. My first time using it, I went through my spoilboard into the MDF base of my XXL :frowning_face: Now I tighten it a little more toward “gorilla tight” – maybe “chimpanzee tight”?

  • It is indeed beech wood.
  • Not sure on the exact RPM, I set my Makita/Carbide3D router to 3.5
  • Feedrate was set to 270 IPM which is what Amana’s speeds and feeds doc says for hardwood.
  • Collet was very tight and was checked before running the job.

Any ideas why it would plunge/fail in the same spot in basically all my runs?

@unllama Yeah it’s not detailed in my post or photos too well but I clamped the crap out of the third run and still ran into the same problem of the crazy plunge. I did 4 bracing clamps on edge side and then four clamps on each corner tightened down pretty hard.

270 IPM is not possible unless you modified GRBL settings ? The default max feedrate is 200ipm, so it was probably going at 200ipm during that cut.

3.5 on the router is around 20.000RPM.

The #201 has three flutes, so that leaves us with a chipload of 200 / (3x20.000) = 0.003"

Nothing crazy, but still higher than I would feel comfortable using for slotting at 50% diameter depth of cut in beech (which in my experience is tough to machine, especially those pieces made of glued strips).

EDIT: also, manufacturer’s feeds and speeds are often given for much more rigid machines than the Shapeoko.

Personally I would recommend you

  • retry with half that feedrate (80-100ipm), and if you want to err on the side of caution also slightly reduce depth of cut.
  • install the endmill, make a paint mark on it near the collet at the beginning of the job, and check it at the end to confirm that it has not moved inside the collet, at all, during the job.

270 IPM… I never go over 50 with bit 201… (to keep the stress down)

So 270 ipm… what was your depth per pass? These machines are belt driven and possibly just acceleration at those speeds could cause a belt slip.

These are all great suggestions and context thank you. This is why I wanted to post because there’s so much I don’t know.

Yeah I was just willy-nilly going with the manufacturers feeds and speeds, definitely didn’t know any better. I do now!

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Forgot to mention it in the main post but .225" on the 2nd attempt and .125" on the third. Not sure what my depth was on the first attempt.

On tries #2 and #3, I think that’s the first time the cutter edge is essentially parallel with the grain of the wood. Like trying to chop down a tree with mostly vertical strokes; the axe mostly bounces off.


Hey I did not notice that at first glance, but if OP used the oops clamps only from the side of the piece, no wonder it got pulled up. Definitely need to place these on the top surface.

You should read @Julien’s e-book on the Shapeoko and linger on the Feeds and Speeds section and the thread has a F&S worksheet calculator so you don’t encounter the same problem. I had a similar experience when I accidentally truncated a decimal in my F&S settings.


Kudos for the eagle eye ! I did not notice that either

I should’ve taken a photo of how it looked when clamped in but I was using 4 clamps on the side to brace the piece and 4 over each corner tightened down pretty hard.

Oh ok then. Good clamping, so that was not it. Less aggressive feeds and speeds and you should be ok.

Ho-ly moley that’s really interesting. Ok. So that helps me understand why it was failing in the same spot. Now I just need to really pull back on my feedrate and depth per pass and try again.

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Thank you! I didn’t know this existed but I will definitely give it a read.

Try running the piece without the end mill in your collet. Then try a scrap piece of msg or soft pint. Good luck.

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