Z settings change during session

hi
hope everyone is doing well. I am having problems on the depth of cut.
The operation consists of 2 parts; 3 pockets and a simple outline of a shape!
dinoa|508x204
The thickness of the wood is .75 inches. I use carbide create to input settings. A1/8 bit is used.

I set all axis to 0 on gsender. The depth of cut on the pockets only goes down about .5 inches. The cutting started fine on the surface though. Then when it moves onto the outlines it starts above the surface.
thanks for the help
Buba

@bubalarry Could you have bottomed out the Z gantry?

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Hey Buba any way you can post the CC file? just so I can see the tool path settings. Not the code.

I’m wondering if the bit is actually slipping the the collet adaptor and has been pushed up making it shorter?

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I had this same issue with a 30° v bit. It was a 1/8 shaft so I used the adapter. Cut would start great and then get more shallow and eventually carved air. I measured the bit at the start of the cut and after it carved air and sure enough it was shorter. It was slipping up into the collet. I tightened it up (more than I thought I’d have to) and the problem went away.

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@DrewBSC It may be, Drew. You can do as @Davek did and measure before and after. I had spotty luck with the 1/4 to 1/8 adapter and went with the 1/8" collet. I’ve had no issues since. Many use the adapter successfully, though.

One thing to be mindful of is that the very short 30° bit can mean that you bottom out the Z axis at some point in your project, especially if you have the router mounted high in the bracket. You lose the true Z0 if this happens and all bets are off subsequently.

The bottoming out issue is also why I added the addition 3/4" mdf between the machine arms. That little extra made a difference.