After getting the 10" CF Flange from the CCE Machine Shop, I added the 2 grooves needed to vent the hole that had the broken tap. The hole that had the broken tap did not need to be rethreaded. I used a spindle speed of 3000 rpm and a feed rate of 2" per minute. I went approximately 0.015" deep like the other grooves, but it's hard to say exactly the depth with the mill I used.