Chamfering 1 1/8" hole in aluminum with fly cutter?

[Drew Eckhardt]

I have some ~1 1/8" holes to bore (boring head), chamfer to ~1 1/4", and tap 1 3/16-16 in 7075-T6 aluminum along with some other milling and drilling on that face.

I'd like to chamfer with the end of a fly cutter. How do I grind the bit?

Like this http://www.youtube.com/watch?v=4W9vjnUKZXc

although my fly cutters mount a square bit at a 20 degree angle.

 

[Tony Wells]

Grind the end at square across the end 25° with generous clearance, short side on the bottom. Adding the 20° to the 25° on the bit will give you the 45° for the chamfer. You'll have to run this at a slow speed to prevent chatter, and don't dwell.