80% lower

What is everyone using to finish their lower units? I'm asking for a friend...
He is knowledgeable in basic machine skills and able to afford decent equipment. He would be willing to purchase the necessary equipment to do a good job and not ruin his lower. What would those with real experience recommend for doing a good job?

I didn't know what to tell him.

 

I presume you're referring to an aluminum AR lower. . . I'd anodize it. With that done, you can either move on with life, or consider the anodizing the world's best base coat for make-up. . . I mean space age paint.

 

Or are you saying the last 20% of work? The best option is a mill, digital readout, and all the required tooling.

 

He has a polymer receiver .

 

The jig that comes with it, a drill press or one of the routers set up for 80% receivers, and the necessary drill bits and mills.

Aluminum lowers are better, and not any harder to work with.

 

He has a drill press but he's concerned that it will be accurate enough to do a good job.

 

With polymer, he could easily place indents by hand to start the bit into.

 

The first problem he will find with the drill press is the chuck will fall out if he tries to put side pressure on it while trying to cut. This can be averted by putting super glue on the taper & pushing the quill down into a piece of wood to force the chuck up into the taper. For aluminum lowers I use an 1/4" end mill but for plastic you could probably use a router cutter for wood.
I use a cheap X Y vice mounted on a small drill press. The press is so small I had to put the vice on at a 45 degree angle.
Notice the red arrow I ground the threads off of this rod to use two nuts so I can have a way to lock the quill in the down position to do cutting passes.


This SubMoa jig uses the hardened steel top plate to let the smooth part of the cutter to ride against that gives a smooth cut, but you have to stay off of it for the first few passes so you don't cut the plate. I would suggest you start with a 3/8" through hole in the area that the trigger goes, this will allow you to reposition the cutter for each pass.

 

I have followed the 80% market since it’s inception, and started using 7 years ago-right about when manufacturers started using 7075-T6 Billet Aluminum. I don’t use the 6061 or Polymer AR lowers, but that is simply my conviction. I use my Mill & Carbide bits then I then sand the machined surfaces. Anodizing isn’t very difficult if you so choose. I also do my own Cerakote.

Remember, it really doesn’t matter how “nice” the machining is. The holes are the important part. I use high end drills, undersized and reamers for a perfect fit.

 

Anderson's metal jig is quality. The included drill bits are absolute junk though.

As said, the trigger pin and safety hole are the most important. They need to be drilled from both sides, or you risk the drill bit wandering off course. This will cause it to be a paperweight. Dont ask how i know.

 

The trouble with using a drill press (depending on mounting method) is the chuck will fall out when side milling.
A mill drill is the least in the choice of milling options.

 

Also, NEVER Climb Mill on a less than rigid machine. If he doesnt know what that is, i suggest doing some learning first.

Putting a side load on a standard drill press causes heat to build, and the spindle to expand, dropping the drill chuck.

 

Like I said in an earlier post I bought a cheap drill press just to glue the chuck in the taper to stop the chuck from falling out.
I have done a few other alterations to make milling in the drill press easier.

 

Not a bad idea. Not proper, but sometimes you gotta work with what you got, eh?

I had a cross slide vise for my DP. It was a piece of junk! It was a cheapie though. When insurance replaced my burned lathe, i opted for one with a mill head on it too. Not as nice as a bridgeport, but it works pretty well.

 

A guy I know very well messed around with the cheaper jigs but finally broke down and bought the 5D Tactical router jig about three years ago. He uses his Dewalt trim router with the unit and has had excellent results. The bit has lasted all this time and the finished products have worked perfectly - both poly and aluminum. The jig and system is (almost) idiot proof. It's the way to go if you don't have a real mill.

 

Ding-ding-ding!!
I think we have a winner!
I will tell my friend .. to check out 5D tactical!
I know he ordered a PSA m4 kit today!

 

Tell your friend to get a large can of WD-40 and a shop apron. I was told it can get a bit messy.

 

It’s messy no matter what. I use cutting fluid the entire time when doing them