Zeroing Circular Live Edge Slab

Hey all. New to Onefinity and the CNC life but excited to be here. Thank you in advance.

I have an X-50.

What is the best process to zero the machine on a circular live edge slab that I want to surface? Piece is 8.5in diameter in the largest section and 7.75in diameter in the smallest. The height ranges from 1.72in to 1.2in. I created a file in Vectric that is 9in x 9in and the corresponding toolpath to surface off 0.55in. Initially thinking zero to the machine bed, as close to where the corner of a 9x9in square would be and have the XY datum in that corner as well. Thinking since the file is 9x9, it should capture the full surface, even if slightly off in the bottom left corner.

This piece was $5 so won’t be too upset if I ruin it but I have some larger slabs that I want to surface and similarly, they may not have hard corners. Open to any and all tips and tricks. Thank you again.
Screenshot 2023-07-09 181404

This is how I would do it if it were up to me…

I would define Job Size as you did.
I would set Z Zero Position to Material Serface
XY Datum could either be bottom left Or Center whichever is easiest to find a reliable spot. Middle might be best.

You now have to determine the bit you want to use to do the flattening. It appears that taking the surface down .55 inch would flatten it.


Thanks Dave! I was leaning towards bottom left for XY because the center of the wood isn’t the highest point of the wood so if I go bottom left, then it starts on the first pass and goes down from there, hitting on the high points until flat. Afraid if I start from the center and zero my Z, it will dig in too much on the higher parts. I guess I could turn the wood to the highest part and zero the Z then move the piece so that it’s in the center of the wood. Sorry! I am a newbie… only have executed few projects in the first week.

I used this bit for surfacing my waste board so going to try this:

Whiteside 6210 CNC Spoilboard Surfacing Router Bit, 1/4" Shank

I’ll report back on how it goes. Thanks again for the guidance.


You can set x and y whichever way works out best for you and then set Z at the highest point on your work piece.

Good luck. You are using the same surfacing bit I use.


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