On Feb 15, 7:23*pm, "RogerN" wrote:
I'm getting close to start cutting metal on the AR-15 receiver forging. *The
first holes will be for the pins that join the upper and lower receivers. *I
have the .251 reamer, I'm considering spotting with a 1/4" end mill, center
drill, drill 5/32, drill with 3/16 end mill, drill 15/64, then ream to
.251". *I'm thinking that drilling with the 3/16 end mill will position the
hole in line with the spindle, if a single point tool would be better, I
could grind a 3/16 end mill to a single point boring bar. *Would this
process get the hole positioned about as a good as possible without jig
boring or grinding? *Would spot drilling, drilling, and reaming be just as
good? *Any better ideas?

Thanks!

RogerN

"Would spot drilling, drilling, and reaming be just as good? Any
better ideas?"

For what you're doing, in I guess a manual Bridgeport, I'd use a 135
degree split point screw machine drill and then ream the hole.