I'm considering doing a build using an 80% lower receiver. I think I can do it but my big concern is the threading for the buffer tube. The rest looks easy. What does it take to do this with quality?
I'll be living in Oklahoma, where they have the "Make My Day" law, by the time I do this so it should be legal.
A sword never kills anybody; it is a tool in the killer's hand.
Lucius Annaeaus Seneca 4BC - 65AD
MAKES AN 80% AR15 ( BILLET ALUMINUM) ALL HOLES ARE LOCATED BUFFER IS STARTED NOT HARD TO TAP THIS ONE
SEE MORE INFO HERE
It would help if you listed the tools you have available.
You need to cut that hole to the minor thread diameter first. Don't recall diameter.
If you have a drill press at least, you can make a jig to hold the receiver perpendicular. Put a center of some sort in the drill press to engage the little hole at the end of the tap, and use the center to hold your tap axial to the hole you are trying to tap.
Now if you have a knee mill, or a large lathe with a 4 jaw chuck I would give a different answer. But then, if you have those tools you would not be asking this question!
Here's all the holes you'll have to drill and tap. You'll also have to either shave down your parts and rear upper reciever lug or shave the interior walls of the fire control well and the rear of the lower receiver.
Front pivot pin - hole drilled with 1/4"
Rear takedown pin - hole drilled with 1/4"
Trigger pin - hole drilled 5/32
Hammer pin - hole drilled to 5/32
Selector - hole drilled to 3/8
Bolt hold-open plunger drilled with 5/32" to a depth of .470"
Trigger guard - left side - drilled with 1/8" through both ears
Trigger guard - right side - drilled with 1/8" through only one ear
Front pivot pin detent - hole drilled with 3/32" to 1.125" deep
Rear takedown pin detent - hole drilled with 3/32" through to detent pin hole
Selector detent - drilled through to selector with 1/8" then countersunk with 5/32"
Bolt hold-open pin - hole drilled to 3/32" with 6" aircraft bit
Stock index hole - drilled with 1/2"
Grip hole drilled - with 7/32"
Buffer stop plunger - hole drilled with 1/4" to .712" deep
Fire control well milled - by .030 with a 3/8" end mill - optionally shave down your parts to fit the undersized pocket.
Rear takedown well milled - by .030 with a 3/8" end mill - optionally shave down the rear lug of the upper receiver to fit the undersized pocket.
Buffer hole reaMed - to 1 1/8"
Buffer hole tapped to -1 3/16" with 16 tpi
Rear takedown pin relief - cut with a 3/8" end mill
Grip hole tapped - with 1/4" By 28 tpi
If the buffer tube threading is a real concern, ShadeTree has the stage 2 80% lower drilled and tapped.
I initially thought that the tapping would be particularly difficult, but after doing it I am confident that anyone with basic familiarity with hand tools could do it as well.
When tapping holes you should back out the tap every quarter turn. Keep the tap well lubricated while doing so.
If you accidentally tap your buffer tube hole crooked you can always back the tap out and re-tap it.
All you have to do is apply preasure in the direction of the error.
My first 80% was about an eighth inch out in 2 directions and I backed it out and placed the tap inside the same threads and ran it through applying preasure once in each direction and not only did it straighten out, the buffer tube still threaded in just as tight.
it can be done with a ratchet rench, the apropriate bit, and the monster tap. slap it in a vise and turn away.
I am currently building my 2nd AR from an 80% cast lower (first was from a completed stripped lower). I just bought a 13" 16 speed bench mount drill press over the weekend and a 4" swivel base drill press vise to hold my CNC drilling jig in. I will be drilling out the buffer tube and tapping this weekend unless something comes up. I don't know that it is necessary to buy all the tools I have (between the cost of the 80% blank and tools I could have bought like 5 complete stripped lowers for what I've spent (I also bought a drill/tap kit, the drilling jig and an airbrush compressor for spraying Norell's) -- proof that people don't do this kind of project to save money but rather for the fun of it). The tools seem like they should make it easier and more fool-proof though. And given that it appears I've got BRD, I expect that I will be using the tools over and over again, and a few of my friends are also interested in building ARs from 80% receivers as well.
Does the table top drill press have a tilt base or does that vise attach to the base?
If I just wanted to save money on it, I could get a Vulcan carbon lower for $80.
I think someone posted elsewhere on this site that Testors sprayer in the model section of the toy store works fine for spraying Norells.