Eric Krewson the "Gizmo" guy once posted a tip on filing nock grooves and I think crooked stic also does something similar. It looked like a good way to do it so I started doing my version of that way too..after gluing on tip overlays and shaping them I cut the groove into the back side of the tip overlays, then I string bow and using a pencil I mark the sides of overlay and limb sides..unstring bow and file between the marks..you still have to pay attention to the alignment of these grooves, go slow and look often. I only use a chainsaw file for cutting grooves. Then I round them with abrasive cord, then 320 sand paper around file to polish the grooves.