Wednesday, September 7, 2016

Made my fixture for threading the buffer end of AR lower

Much like me, it ain't pretty, but it does work. I took a piece of 1.5 inch round stock and milled .125 off a section of it. This gave me a flat area to screw the lower to, and, it also centers the buffer hole (which is .625 above flat) when bolted together. Still have to center it side to side, but, that is pretty simple.

 Next, I needed a way to clamp the lower to the fixture. I fashioned a plug that will fit in the roughed out magazine well. For the next lower, I will use the same fixture, but, I will drill and counterbore through it and tap mating holes in the solid pocket area of the lower.

I drilled the holes to match those in the fixture. I bolted everything together, then, removing one bolt at a time, I used an end mill to make a flat so the bolt would tighten down straight, instead of angled, so it is nice and solid. Repeated for all three holes.

Ready for lathe. Like I said, she ain't pretty, but it is solid. Much more rigid than I thought it would be. I milled a couple flats on the side to put a brace on each side if needed. The flats are the same exact width of the outer surface of the lower. For now, I don't think I will need them, but if need be, they are there. I have some 1/8 flat stock I can easily make clamps with.
Here it is mounted in the lathe. It clears the bed easily. It is very rigid. I indicated the face true and centered the hole side to side, then, tightened everything down. One more check to make sure nothing moved.
I couldn't resist trying it out. Too late to finish the hole, but, I had to know if it was going to work. Once I got the hole trued up that I drilled in there (The drill kicked the piece to the side a bit and the hole was way off) when it was in the mill, it cut clean with no chatter. That is, until you hit the area where the threads are only on one side as it ramps down. It pushes off a bit here. It works out though. I am careful and slow the feed down (I kick the feed lever out and feed really slowly by hand) in this area as it lopes through the ramp. It forms an undercut on that side from the slight kick. Hard to describe, but I will take a picture of it when done. I hope I can figure out where I put my good boring bar. I have a threading insert in it, and it is the perfect size for this job. Thick enough to be rigid, but small enough to fit. Thought I had it in my Gerstner box. I have a few more places to look. I would like to finish the buffer area tomorrow. I am off again this weekend, if they don't change their mind. Hopefully my end mill arrives and I can finish the magazine pocket. Then I can blue it and assemble it. I still need to engrave it as well. Haven't figured what all to put on it yet. Been getting ideas online. Lots of recommendations of putting a serial number on it. One guy had a decent idea. He engraves his NRA member # followed by what number receiver he is on. That way, if law enforcement looks at the gun, you don't get grief for no serial #. Using a number you can remember helps if you need to report it stolen, so the NRA # is on your card, and unlike your social security #, you don't really care if someone sees it.

No comments:

Post a Comment