On Fri, 15 Feb 2013 21:23:00 -0600, "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


Such close dimensional and positional accuracy may be
required for intechangable parts, but if you are not going
to be swapping uppers/lowers, etc. it may be possible to
drill the holes close and then assemble the upper/lower,
clamp and align [hand] ream the holes. IIRC spring or
spirol pins are used so super accuracy should not be
required. There are also "kits" with oversize pins to rehab
loose guns that may be helpful.

http://www.brownells.com/rifle-parts...-prod7589.aspx


--
Unka' George

"Gold is the money of kings,
silver is the money of gentlemen,
barter is the money of peasants,
but debt is the money of slaves"

-Norm Franz, "Money and Wealth in the New Millenium"