I was solving the same problem with GTAC. It is hard coded value and there is a new enhancement request for it ER8863869
here part of comunication with GTAC:
The question was How to change automatic chamfer (Csink) diameter? (as IR 8863869)
( hole diameter was 10mm and csink diam was 12)
Value of 2mm is hardcorded / needs to be forwarded as an ER/ ER Template
I have analysed the data and talked with the experts from the development.Unfortunately, the value of 2mm is hardcorded and there is no workaround for this behaviour. The current behaviour is 'Work as Designed'.But the development feels this issue needs to be addressed.We would suggest to forward this issue as an enhancement request
So I hope it helps
For everybody reading this discussion... just to clarify:
This hardcoded Csink diameter applies ONLY to situations where you have NOT modeled a chamfer in your CAD model !! NX CAM needs to assume an initial Csink diameter which the user can subsequently change. With no information available in the CAD model, all we can do is offerr our best guess so we take 2.0 mm more than the hole diameter. Users than need to change it if they want a different value.
The enhancement request is to allow individual customers to configure a different default for this situation.
NX CAM Development
Tom van 't Erve