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

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.

On Feb 15, 8:20*pm, jon_banquer wrote:
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.

If you need more positioning accuracy than say .005 you should spot
drill first.

If you are using a CNC, I'd would interpolate the hole with an
endmill. I see no reason to use a single point tool for what you are
doing.

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

do this with a stub length drill

"jon_banquer" wrote in message
...

On Feb 15, 8:20 pm, jon_banquer wrote:
snip

"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.

If you need more positioning accuracy than say .005 you should spot
drill first.

If you are using a CNC, I'd would interpolate the hole with an
endmill. I see no reason to use a single point tool for what you are
doing.


The drawing calls for a diameter of .251 +/- .001 and spacing between the 2
holes is 6.375 +/- .002, I'm hoping to do a little better than that. I'll
be doing this on a low hours Enco "Bridgeport" style mill.

While at my shop last week, I turned on my CNC control (Anilam Crusader II)
and it doesn't look good, display (7-segment LED's) was dim with various
numbers, didn't respond to a reset... So it's probably upgrade opportunity
time. The old control had a 1000 line memory with no drip feed, ok for hand
entered code but very limiting for computer generated code. So the
EMC/LinuxCNC conversion should be a big improvement, plus I can add a
spindle drive to run on single phase plus have speed control.

Thanks for the info!

RogerN

On Feb 16, 6:06*am, "RogerN" wrote:
"jon_banquer" *wrote in message

...

On Feb 15, 8:20 pm, jon_banquer wrote:
snip

"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.

If you need more positioning accuracy than say .005 you should spot
drill first.

If you are using a CNC, I'd would interpolate the hole with an
endmill. I see no reason to use a single point tool for what you are
doing.

The drawing calls for a diameter of .251 +/- .001 and spacing between the 2
holes is 6.375 +/- .002, I'm hoping to do a little better than that. *I'll
be doing this on a low hours Enco "Bridgeport" style mill.

While at my shop last week, I turned on my CNC control (Anilam Crusader II)
and it doesn't look good, display (7-segment LED's) was dim with various
numbers, didn't respond to a reset... *So it's probably upgrade opportunity
time. *The old control had a 1000 line memory with no drip feed, ok for hand
entered code but very limiting for computer generated code. *So the
EMC/LinuxCNC conversion should be a big improvement, plus I can add a
spindle drive to run on single phase plus have speed control.

Thanks for the info!

RogerN

"The drawing calls for a diameter of .251 +/- .001 and spacing between
the 2 holes is 6.375 +/- .002"

On your Enco knee mill I'd center drill, drill and ream.

On a CNC I'd interpolate the hole with an end mill.

"RogerN" wrote in message
m...

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

Here is an old way to position holes as accurately as you can measure,
requiring only a lathe with good spindle bearings and a trued and
tested faceplate.
http://www.neme-s.org/Model_Engineer...%20Buttons.pdf

My milling machine won't bore a straight cylindrical hole because the
quill play increases as it extends. I can bore to more constant
diameter by raising the knee, or using the lathe. I didn't notice the
tiny effect until I rebuilt a hydraulic pump to closer than my usual
hobbyist tolerances.
jsw

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"

On Feb 15, 8:23*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

They do make machining and drilling jigs for the AR home machiners.
You'll need something like that to get the buffer tube threads square
with the world. Some guys had them to rent, too.

Stan