it just uses c axis so it doesnt cut the keyway correctly

nope dont have multiaxis just mill 3d and lathe

how would i go about a keyway on a lathe that twists around the shaft then ends up straight? 1.25 keyway i had it do c axis contour then just added a -.25 on the y till the end of the key then shifted y+.250 then followed same path(center) out but that didnt work. was only cutting it 1" wide where c rotated. is there a way to do it or do i just have to use the end mill the size of the keyway

i see a lot of people use wear, might be a dumb question but what if using a certain size end mill then run out of them and have to switch to a different size? ive been using control. im guessing this is just for mill also? what about lathe?