Shop Debate: Cutter compensation when rotary milling on a lathe

Hello, I am in a current debate within my shop and am looking for outside input on this scenario. The machine is a twin turret lathe, the upper turret has an X and Y axis and the lower turret only has an X axis. The current set-up is using a live tool holder with an endmill on the upper turret with the tools axis line colinear with the sub spindle. The question that is up for to debate is how to adjust this tool when it is doing some complex rotary milling using the X, Y, and C axis'. One side of the argument states that you need to dial the X and Y axis of the tool center to the C axis then adjust X to compensate the tool. The other side states that you need to dial the X and Y axis of the tool center to the C axis then use the radial compensation to adjust the tool. Any input would be greatly appreciated.

You're milling with Y and C at the same time? Usually one or the other is used. Is polar interpolation used? When using polar interpolation, it's best to use cutter comp. As the tool cuts an outside square, for example, the contact with the work piece isn't always on the bottom of the end mill at the 6:00 position (assuming x axis is straight up and down). So, if you compensate along the X, the shape can start to get distorted. It probably won't be noticeable with small compensation amounts, but I have seen problems when using reground end mills or changing end mill sizes. Usually, if the program has no cutter comp, and a reground end mill is put in, the program needs to be rewritten for that size end mill.

I don't know your part shape or what your program looks like, but I'm struggling to think of a scenario where compensating in the X would be better than with radial tool comp. I think you could test it out both ways and make a large offset adjustment to see which one makes a part without any distortion of the shape.

If you're using polar milling, use radius comp.

Comping in X is sloppier and more prone to error.