You can do some test to determine if the culprit is machine deflection, or programming related.
To check for machine deflection…
Try making the hole, then running the same toolpath again, if new material is cut on the second run, its a signal that the cutter is deflecting.
Try running the cutter slower, and see if the diameter gets closer to your intended result. If so, the cutter is likely deflecting towards the center of the hole, creating a smaller diameter.
Try switching from “conventional” milling to “climb” milling (or vice versa) See if that helps. Again, this might indicate deflection.
If none of the above make any difference - the problem is more likely programming.
Cam software often uses a “leave stock on walls” option that you may have accidentally selected.
.050 is a lot to be off, is the hole round or oblong, do you do a separate last pass say .005 per side, is there a lot of slop in the ball screws, can you move the router motor any way, front to back or side to side?
Pat
Thank you for the response. I have done each of the steps you suggested and I was not able to detect the deflection in the bit nor is there a difference in the hole after switching from climb to conventional.
So today I did make the same vector and modified all the settings based on all the suggestions in the comments section of this post, I cut .75 at X-RPM (#3 on the turn dial for the Makita, sorry I dont have the rpm chart memorized and cannot recall the RPMs) So after modifying all the settings It is cutting at .69. using the Jenny upcut at .25 DOC
