Hi Guys, me again.

Ok, I'll bite...with those nifty "Jig Blocks" you see on Ebay from 85.00 up to 120.00, that have all the places to drill the holes...

How the #*$#@! do you tap the buffer hole straight??'

Without a jig, I mean...is there a way so that I don't have to go the Mujadiaheen M16 way?

Any experienced 80% builders out there willing to share a little of their magic?

Panz

I used my OSI jig for one of my lowers.  I pinned the lower using the front and rear takedown pin holes to the jig.  I then clamped the whole thing to the table of my drill press.

At work (I have a Bridgeport at my disposal), I clamped the lower in a vise, picking up of the top plane of the lower to insure that it was mounted vertical and square.  I then bored the hole out, to correct the center location.

Tapping the hole afterward is easy.

Edited for spelling.

The easiest way to do the buffer hole:

The rear surface of the buffer hole must be square in both dimensions to the upper, do this first.

Pin an upper to the lower and use a piloted expanding reamer to size the hole concentric to the upper.

Remove the upper and securely clamp the lower to a bench.  Build a long "V" block in line with the buffer hole that will support and align a long extension for the tap.  Use lots of cutting oil and tap the hole.

If the threads are a little off, the alignment can be corrected later by re-cutting the threads slightly with side pressure on the tap in the direction the alignment must move.

You can easily check alignment by screwing the buffer tube in and measuring/gauging to the lower.

PanZer, I don't think many people know about it because we haven't really done any advertising. But there is a very good video series out on making an AR-15 from a raw forging. You could also use the info to build your 80%'er and get to "see" it being done. Might be helpful. The videos got really excellent reviews over on BuyIndies. It may answer a lot of questions for new builders too.

Here is a link if you want to see em.

[url=http://www.roderusproductions.com/videosdtl.htm]AR-15 Videos for raw forging[/url]

Here's what I did (but I have three of the 80% lowers and another coming, plus a 3in1 lathe/mill): I bought a 1 3/16x16 tap, a 1 1/8" end mill, a 6" piece of 1/2" drill rod, and a DPMS cleaning rod guide.

Finsih drilling your lower; fit the upper. Pin the two together, insert the cleaning rod guide. Clamp the 1/2" drill rod in your 3in1 lathe chuck, hang the upper/lower/rod guide on the rod. Now clamp the lower to an angle plate on the crossfeed, and clamp that down. Remove the upper & rod guide, replace the drill rod with the end mill, mill the buffer hole. Replace the mill with the tap, run it in and tap the hole.

Works slicker than owl shit.

You can also hold the tap in the jaws of a mini-lathe and then mount the lower directly on top of the saddle (remove the cutters and holder first). Then hand turn the lathe chuck with one hand and turn the saddle wheel slowly with the other hand. Works like a charm and gives a nice straight hole.

I used a cordless drill and Vermont American (brand?) 1" grinding stone and cutting oil to open up the hole to almost an inch.

Then I built a piloted reamer setup, which is now in circulation with Bravo squad. It is comprised of two shell reamers (1 1/16 and 1 and 1 1/8) that I scored on eBay for $5 each, a threaded 5/8 rod, and about 6 inches of 1 inch diameter copper pipe with an adapter silver-soldered into each end. I ran the smaller shell reamer through the rear tower with the upper clamped slightly forward of its usual position, rear takedown lug inserted into the fire control area. Then repeated the process with the larger reamer.

To tap the hole, I clamped the lower onto the base of my drill press with the rear tower pointed up. I set the tap into the BTH as straight as possible, lots of leveling and measuring involved. I chucked a small piece of 1/4 inch steel rod with a point ground onto it into the drill press and centered the point on the small dent in the top of the tap. I held pressure on the tap with the drill press handle and turned the tap with a crescent wrench. The method is pretty well shown on the Builders Squad Project site. Worked great for me. Oh yeah, I drilled out the buffer tube retainer spring/pin hole before I tapped the BTH.

Far and away one of the most enjoyable projects I've ever completed.

Here is the 80% oracle.

[url]http://quartz2.cyberstation.net/~dwpaul/bs-home.htm[/url]

I made up a piloted reamer from mostly off the shelf parts to get the buffer hole straight. If I did it right it should show up in a picture below.

[img]http://www.hunting-pictures.com/members/Backwoods2/artools2.jpg[/img]

The reamer is a hole saw (1-1/8 inch)which I threaded onto a piece of 1/2 inch rod I bought a a local surplus place. The end was already threaded (1/2X20) to match the hole saw and I used a forked rod end with a cross bar for the handle.

The short cylinder by the tapping wrench is the guide bushing that fits in the upper rec. It's just a length of 1 inch rod with a 1/2 inch hole thru it. I grooved the ends for O rings to protect the inside of the upper, maybe not needed, but I'm picky about things like that.

I also made the drilling jig(didn't use it though) and the tap wrench in the picture while I was waiting on the 80% lower to arrive.

Don in Ohio

OK, I tried to view this post from work and there was no picture. Can anyone else see the pic or was it just the PC at work not co-operating?

Picture shows up fine!

Did you turn the hole saw by hand??? That must have taken a while...

Yeah, by hand really didn't take near as long as you might think. Far less chance of the teeth grabbing and causing damage that way.

Don in Ohio

Good tip.

I think I'll try that method for rough-cutting the 1/2" [forged lowers] hole out to 1"...As you say, there is some chatter, even with a 4-flute end mill; I'd like to get the hole almost to size (say 1" or 1 1/16") before milling the hole out...