I have noticed this problem for a while and haven't figured it out yet. My lathe tool is cutting past the stock, in thise case around .015" which I think is common in all cases. The extend distance is set to 0 for the retract. not sure what parameter would do this.
It's picking up on the radius of your insert, not an operation parameter. I made an operation with a normal .031R insert. Then copied both tool and tool path, changed only the radius on the insert, and now it doesn't cut past the end of the part.
Have you tried in a later release?
NX 8 is no longer under development, so things might already be there in NX 9 or 10.
Production: NX10.0.3, VERICUT 8.1, FBM, MRL 3.1.7 | TcUA 10.1 MP7 Patch 0 (10.1.7.0) | TcVis 11.4
Development: C (ITK), .NET, Tcl/Tk Testing: NX12.0 | AWC 3.4 Preparing: NX12.0
Employees of the customers, together we are strong
How to Get the Most from Your Signature in the Community
NX Customization - Best Practice Guide