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80% Lower milling

Old 03-09-2014, 03:53 PM
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80% Lower milling

I've disassembled and reassembled LOTS of AR pattern rifles, so I'm familiar with them, and comfortable doing light smithing work on MY assorted firearms. I'm not interested in the debate or legality of 80% lowers. But, I'd like to hear on a, say, 10 banana scale, how labor intensive cutting an 80% lower to completion is, from anybody here that's done it. I like to "roll my own", so costs aside, how long did it take you, and what was your method? I don't need pictures, I understand that you likely want to keep your business yours. Anybody?
Old 03-09-2014, 04:36 PM
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I haven't done it myself but I've heard it takes around 20-30 mins on a CNC.
It can be done with a drill press or better an end mill. Do you have a jig for your 80 and what route are you taking for machining?

From what I've seen, I don't feel it's "labor intensive" at all.
I consider labor intensive digging holes in the ground, not measuring a piece of metal and maneuvering the arm of a drill press of the like.


Old 03-09-2014, 05:03 PM
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Don't waste your investment hacking it out on a drill press even with the jig 7075 is too tough for a drill press to do a goo job on unless you absolutely have NO other options
Old 03-09-2014, 05:06 PM
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Colfax tactical has really good links to instructions and prints
Old 03-09-2014, 06:14 PM
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Well, the one I was eyeballing came with jig(s) specifically designed for the drill press method. I don't really feel like paying to use a mill, and I have no CNC access. We have an old end mill at work, but it's locked up at night, there's only two old farts that know how to run it. Somehow, I think asking them to instruct me thru it wouldn't happen. Not at work. I do have access to a pretty good drill press, so I was exploring that route. I know it ain't a cheap lesson to learn, but worst case, it'll be a $150 dollar lesson. I know. You just told me not to do a hack job on a press, right? Thanks for the name drop to related companies. I'm still seeing if its something I'm up to doing.
Old 03-09-2014, 06:24 PM
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The problem is that drill presses aren't made to side load so you can only drill with them. You try to side load with an end mill and you will take out the chuck! That means your lower will not only look like crap when it is done but the tolerances won't even be close. The fire control pocket doesn't have to be that accurate but the rear portion where the upper meets the lower is about .005 tolerance fit and location to the take down pins. It is much better done on a mill but I am a machinist that's what I do for a living. I am lucky enough to even have a Bridgeport of my own.
Old 03-09-2014, 07:01 PM
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I don't know why I stuck "end" in there. It's just a really old mill. All the plates on it are in Italian and German. Eet ees oooold. But it sits in the shop, behind locked doors, due to employees thieving from the stock of drills, taps, and other non-cheap tooling. Which sucks. Only two guys know how to run it, and my employer isn't the openly firearm friendly type. So it's pretty much out.
The lower I was looking at came with the jigs/templates to drill about 12-13 pilot holes, the firing group pin holes, then another template to drill out the pilots to achieve rough inner dimensions. Overlapping hole method. Another to drill the rear notch out. And lastly, a template to mill it out, or to guide for hand finishing. (I'm a sucker for hand finishing, especially metal). I think it might be an interesting project, but it would be nice to be a first time go. No rush on my end to finish it. I can pick it up and sit on it until I'm better set up to cut it.
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