Put the block in the vice, place a good quality countersink in the collet, my rear vice jaw is always set Y zero as is right hand side vice stop X zero, set the depth of cut and lock it, set Y to give required cut when happy make note of reading say +3 then go round each face adding 3 to each block dimension + or – and you end up with four chamfers all same size, turn block over repeat you now have eight. It may sound long winded but when you have a lot of tooling to chamfer you want them to look the same otherwise it's a pigs ear, same can be done with rads.
Colin