.

"It is well worth the trouble and expense of getting someone with a bench-mounted, pillar drill to do it. It's quite difficult to keep the bore co-axial and if you don't, the brake will sit at an angle to the wheel, which is er... "sub-optimal"."

Very much this. I got esteemed frame builder Mike Burrows to set mine on his pillar drill, and he still managed to fuck it up, even with all the correct tooling and decades of experience.