Bit Not Cutting All The Way Through

I have been having trouble cutting all the way through my material and cannot figure out what the issue is. I set my settings to the exact depth of the material, but Im still left with about o.o5" of material. For example, if I set it at .75" , it only really cuts down to about .7". I am using the AutoZero Touchplate and I have leveled my spoilboard to be parallel to my bit. What else could it be?
Thanks in advance.

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Is the bit slipping? Or the collet worn or dirty? I had that problem and replaced the collet, problem solved. They do wear, or get oil and saw dust in them.

Have you checked the calibrated movement of your Z-axis? gSender has a great calibration tool. Also if your workpiece isn’t perfectly flat you’ll get variation in cut depth depending on where you zero.

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@inthewoodworksco, have you verified that the thickness of your piece is actually .75"? I know I have made that mistake before, thus getting me to purchase a digital calipers to accurately measure my thicknesses. Please let us know how you come out, we all may have this problem at some point and would like to see the resolution.

For me the resolution to this problem is to reference the spoil board instead of the top of the material to be cut. Assuming that your stock is ~0.75" and you entered a cut depth of 0.75" in your CAD/CAM program, the solution I use is to put the bit just touching the spoil board and instead of hitting the zero Z button, click on the number in gSender and enter -0.75".

When you think about it this makes sense because if you zero to the surface and cut 0.75" you ‘should’ end up at the spoil board with a depth of -0.75". The difference is if the stock is not exactly 0.75" you cut more or less on the first pass instead of not cutting through or cutting into the spoil board on the last pass.

It works for me and saves my spoil board.

EDIT: Just to be clear with this method you still choose to zero of the top of the material in your CAD/CAM software.


What @_Michael said works amazing - saw it on CNC Nutz on YouTube. Also make sure your bit is actually reaching the spoil board and not bottoming out on the Z Gantry.

That’s where I picked it up by way of @gwilki, one of the best tips I’ve gotten so far from this wonderful community!