80% AR Help

[pacific_v]

I came across this site from other google searches regarding the completion of 80% AR lowers. I'm not brain dead or dumb on what needs to be done but as of recent I almost feel that way. I've got a bench-top drillpress and a manual Taig mill, along with some TaticalMachining jigs. Well for as simple as things seemed I am having the most biggest problems with the raidus's on the corners of the pockets. I am not sure if I follow along the edge of the jig while milling and go straight to the corners or if I come in a small bit towards the center of the pocket before making my way to the corners. My first attempts failed as I milled too much and my main pocket wall was too thin. My other attempt faild because I ran my endmill too much into the corner of the jig.

I also need some input regarding the radius's exact size. I hear of people going a 3/8" radius but heard for things to be within Mil-spec it should be a 7/16". I'm using a 7/16" endmill currently and am almost feeling like if I should just start drilling out the 4 corners of the pockets and then mill the rest of the material out given how much of a hard time I'm having with the corners.

Any and all help would be greatly appreciated.

[mrwetwork]

The radius doesn't matter that much. Mil spec is like .312 radius a 3/8 endmill has a .1875 radius. If I were you i'd slot the middle of the pocket then step over lightly on the sides. You can drill a hole in the FCG to enter with your end mill which will make your slotting easier so you aren't plunging into solid material.

If you start from the middle and work your way out you can make the pocket a little easier and less chance of messing up the sides.

Also to center your lower on the jig you can try spacing it with business cards or paper.

[VaderSpade]

Follow the edge of the jig BUT take small bites and go slow. Lots of pull on the end mill in the corners. Watch for pull out. I mark the depth my end mill with a sharpie. I have a good sized mill and I only go down a 1/4" at a time leaving a little material along the edges, and then clean everything up at the end.

The corners are not that critical. I use a 5/16" end mill for nice clean corners.

Check out this thread;

http://www.tacticalmachining.com/forum/viewtopic.php?f=10&t=11

[ford63man]

I like to drill out my corners first in a few thousandths. than run a couple passes around the sides with my end mill. than I take the top of the jig off so I can see what im doing, and finish milling. I use a grizzly g0619.

[pacific_v]

I know if I can get the damn corners figured out I'd be golden. I know you folks got bigger mills and theres quite a bit of an advantage given you folks can take deeper plunges. The most my Taig will do is a plunge at 1/8" so I was thinking if I should just drill most of the large holes and skip all the little ones and then clean everything up with the mill.

What would you folks think about drilling all the corners on the drill-press to about half the full depth and then me doing light shallow plunges with the endmill till I reach the required depth? I take it I would just need to make sure my endmill turns freely while the mill is off and the bit is inside of the hole and then proceed to turning the mill on the make the plunges?

[fonzy]

I move my 3/8 bit right up to the corner (radius) as close as I can with the mill off and then back off a 1/4 turn. I then turn it on and slowly lower it. Then I start at the other end and do it all over. Then I simply connect the dots. I go down about 1/4 down at a time. Your first hole you did on each corner will be your guide so you always return to the same spot. Once I connect the dots I turn it off and return back to the first hole and do it all over again. So go down 1/4" make your hole then raise it up 1/8 and make your pass. So that your hole is always deeper than your pass. It takes a while but it comes out clean. Once you have done your first pass you can take off the plate and do the entire thing without the top plate, that way you never jack it up. Your first pass essentially becomes the guide.

Second make sure you feed the metal into the bit.

Check my stats I have some threads, some good some bad on the 80s I have done.

I also outline the guide with a marker.
Look towards the rear of the receiver and you can see I scribed the outline into the black.

Here you can see me following the outline of the first pass like I said above.

[kcstott]

Fixture not needed

[toddh]

I came across this site from other google searches regarding the completion of 80% AR lowers. I'm not brain dead or dumb on what needs to be done but as of recent I almost feel that way. I've got a bench-top drillpress and a manual Taig mill, along with some TaticalMachining jigs. Well for as simple as things seemed I am having the most biggest problems with the raidus's on the corners of the pockets. I am not sure if I follow along the edge of the jig while milling and go straight to the corners or if I come in a small bit towards the center of the pocket before making my way to the corners. My first attempts failed as I milled too much and my main pocket wall was too thin. My other attempt faild because I ran my endmill too much into the corner of the jig.

I also need some input regarding the radius's exact size. I hear of people going a 3/8" radius but heard for things to be within Mil-spec it should be a 7/16". I'm using a 7/16" endmill currently and am almost feeling like if I should just start drilling out the 4 corners of the pockets and then mill the rest of the material out given how much of a hard time I'm having with the corners.

Any and all help would be greatly appreciated.

Here you go....



Place lower into fixture. Place fixture into vise, and set fixture against vice stop
Use edge finder to locate the Y-AXIS.
Then move Y-AXIS .100 out for edge centerline. Set Y-AXIS to ZERO
Then go to part centerline (edge at 0.000 + 1/2 width of part).
Set Y-AXIS to ZERO.
Install 7/16" endmill. Bring the cutter down to part and touch it.
Set Z-AXIS to ZERO.
Move cutter back to BUFFER pin hole, set .040 to .050 from hole.
Set X-Axis to ZERO.
-----------------------------------------------------------------------------------------------------------
1ST CUT --- Y-AXIS to --0.025 and stays there
X-AXIS moves from 0.000 to --3.050
Z-AXIS moves down from 0.000 to --0.635
(Z goes down 0.050 per cut)
*finished width .4375 +.010
-----------------------------------------------------------------------------------------------------------
2ND CUT --- Y-AXIS moves to + 0.050 and stays there
X-AXIS moves from 0.000 to --0.565
Z-AXIS moves down from 0.000 to -0.635
(Z goes down 0.050 per cut)
*finished width .500 +.010 -.000
------------------------------------------------------------------------------------------------------------
3RD CUT --- X-AXIS moves from --1.425 to --3.080 (final cut --3.100)
Y-AXIS moves from 0.000 to --0.120 (final cut --0.125)
Y-AXIS moves from 0.000 to +0.120 (final cut +0.125)
Z-AXIS moves down from 0.000 to -1.249
(Z goes down 0.050 per cut)

*Finished width .685 +.010 -.000
-------------------------------------------------------------------------------------------------------------
4TH CUT --- X-AXIS moves from --1.425 to --0.950
Y-AXIS to --0.025 and stays there
Z-AXIS moves down from -0.635 to -1.249
(Z goes down 0.050 per cut)
-------------------------------------------------------------------------------------------------------------
5TH CUT --- Install 5/16" 3 flute cutter w/ 2.3 in. of stick-out.
Reset Z-AXIS to ZERO.
X-AXIS moves from 2.200 to 2.450
Y-AXIS moves from 0.000 to -0.010 to +0.010
Z-AXIS moves down from 1.225 to 1.375

[pacific_v]

of all the small holes I was looking to do the main 14 small holes and then enlarging those to conform the corners to spec. I'd like to know if its possible to go a 7/16" when enlarging those corner holes or if it must be the 3/8" if I was to go this route.