it was a 25x25mm bar and he said he just clamped it in the center so it obviously just defected, and he rotated it around to do each side rather than just clamping it properly and getting it lined up and do one side then just jog it over and do the other. Oh well im hoping I can re use the bit of stock he messed up as at least its not under sized I don't think. All the more reason to build a better machine myself.

I cant use the corner cutter I got as it will not fit in er20 collets so going to have to use a straight and a ball nose.
I don't quite understand the last bit your saying but the part has to fit down a tube with a fairly tight tolerance.

many thanks