I am trying to make a groove on a 340 Dia bar on a CNC lathe machine Lepond with Sinumerik 810T controller. The groove radius is 6.68mm and the sharp corner is rounded by 1.5mm radius. I use a button tool with 9.5mm (4.75radius) width. When I check the profile after machining, I found that the width of the groove is increased by around 0.25mm. But this is not uniform along the profile. I have NC program with nose radius compensated manually and without compensation generated using CAM software. Coordinates from the both method found ok. Compensation parameter like tool type and radius were entered on the machine.

I suspect synchronisation during the circular interpolation. Is there any method to check this?

Or is there anything should I check?

Please help.