Trouble Getting Precision Cuts - Deflection of the Bit?

I finally decided to try my hand at inlays, but I can’t get the male and female to fit together properly. After a couple of tries with no success I tried to cut a simple circle inlay so I could see what was happening. The shape I get is not a perfect circle so the inlay did not work.

Had a similar problem trying to cut hidden box joints last week. The joints needed a lot of fine tuning after coming off the CNC.

I am left thinking that maybe the bit is deflecting? Everything else is tight as I just went over the machine to rule that out.

What bit are you using to machine the male and female inlay parts?

Is this a V carve inlay?

I am using a 0.125 flat endmill.

Started with a vcarve, but then went to a straight cut to simplify the troubleshooting.

Care to share the file and the settings?

I’d like to share these resources on v-carve inlays in case you don’t have them.
VCarve_Inlay_Description_and_Procedure.pdf (1.1 MB)
VCarve_Inlay_Cheat_Sheet.pdf (188.8 KB)
If you decide to try a v-carve inlay again those two documents have served me well.

I have never done a regular inlay so I’m not much help with those.


@MajorSciGuy You are on the right track going back to a simple circle to start your problem solving. Since you have said that everything is tight, I would run the calibrate tool to ensure that yourLM is moving as it should; that is, you tell it to move 10mm and it actually moves 10mm.