post production number off

I am in the process of making spoil board. I am new at fusion 360 cam. I made 2 test holes . In Fusion 360 i have the holes 22mm outside and 10mm for the inside. the cnc made holes 19.86mm outside and 8.4 inside.(see pic) I am using a 6mm flat tip in fusion and in router. I will do a stepper test tonight. Is ther anything in fusion that i overlooked. Ideal settings for MPCNC? Thanks in advance

I was just doing something similar last night. I discovered that my tool path in Fusion had .5mm stock to leave enabled by default. Turning that off helped some, but still didn’t get it quite to the proper dimension.

No matter what machine you’re using, there’s always some amount of deflection to deal with, both from the machine and the tool itself. Running a finishing pass as well as slowing down the cut can get you closer to the actual dimension you need. Tool sharpness, runout, and stickout can all play parts as well.

Based on a lot of machining videos I’ve watched, it also seems common to have to sneak up on your final dimensions using negative stock to leave if you’re going for really precise parts. Of course, for a spoil board, you probably just need your inserts to fit rather than super precision, but it’s a good piece to practice on, too. Now if only I could decide which style of spoil board I want to make!

Oh, and you might also want to check your depth of cut too.

The more experienced folks than me probably have some more advanced tips for dialing in your machine.