Z cut too deep on final cutout

Hi, I have S4 XXL. My cut is going fine and the Z Axis had no issues on the entire project. However, when I made the final cut out the outer frame, it plunged much deeper than programmed and ate into the wasteboard. I purposely programmed the cut much shallower in order to not have a full cut through (this was just a draft). But it still plunged past the bottom of the stock.

The only thing different about this particular cut is I pulled the bit out a little bit more in order to reach down deeper into the cut. However, I have a bit setter and it checked the measurement before the cut.

Stock - 29.7 mm
Tool: #201 End mill (1/4)"
Start Depth: 0.000 (top)
Max Depth: 25mm (Offset/Right)

Zeroing was completed prior to cut - since there were no issues on the details, that’s clear it’s not the problem. Any ideas?

Project X.c2d (176 KB)

A tool shouldn’t pull out at all — make sure that everything is clean (esp. no oil) and that you’re using the correct size collet (easy to mix a 6mm for 1/4" for example).

Use the button only to hand-tighten so that things will stay in place while one fully tightens w/ a pair of good quality wrenches (13mm low profile and 22mm stubby) — a firm squeeze should suffice.

All things being equal and no mechanical issues I have using bottom for cut through projects. My spoilboard has no marks on it since using bottom. It does take a workflow change so you dont zero on top out of habit.


Yep, I did all that. But I don’t understand why the Z would be deeper than programmed. The bit did not slip at all.

Did you use the load new tool when you pulled it out or was this a requested change by the program? Even though the bitsetter checked again if you did not do this it would still think your old bit and zero settings were accurate.


It was a requested change by the program.
So even if its a pre-programmed Carbide tool - if I have that particular bit pulled lower than normal, I have to program it as a new tool? Something other than #201?
Is that my understanding?

The bitsetter measures the difference between bits during a requested change whether by the program or user.

Example. If you were to set your z zero on your piece then just loosen and move the bit in the router when it returns to the bitsetter at the start of the next toolpath your cut will be off whatever the difference you moved it. Without the program knowing you changed the bit it wont adjust the zero.

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Oooh ok. I did not realize that. I thought the bit setter just measures the tool length, regardless how its set in there. Thank you for that clarification.

So, I want to dig a little deeper into the stock (this one is about 1.5 inches) without burning the surface of the wood with spinning router collet nut… is the solution to buy a longer bit for that purpose? I feel I am answering my own question here.

Is there an alternative option?

The #201 has a flute length of .750". Cutting that deep will cause the tool shank to rub the inside of your cut, not a good thing. You’ll want your flute length greater than your depth of cut to get those chips cleared out.

The BitSetter is not measuring the bit as such. It is only measuring the difference between the last time z was zeroed and the new bit making an internal offset between the two maintaining the original z zero. So the only measuring of the new bit is the delta between the 2 not absolute bit length.

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Got it. Thanks for the information folks. As you can tell, I’m still new at this.
Looks like I need a longer bit.

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