Sunday, May 13, 2012

It's difficult to make lemonade out of lemons without tools.

I've been busy with handling various life issues lately, but I did manage to slip in some time yesterday to do some machining work on one of my AR lower receiver forgings. I got all the necessary holes drilled, including the buffer tube hole. Originally, I set it up on the mill and got the buffer tube hole lined up and drilled out to 5/8" before taking it to the lathe. A large block of aluminum allowed me to chuck the lower up and get the buffer hole centered before boring the hole out to 1.125" in preparation to cut 1.1875x16 threads. I went ahead and threaded the receiver in the lathe, and it turned out nicely.

Having a lathe around to do this with makes a tough job much easier, but I thought I could make the job even easier and if nothing else, I could have some fun building something.
I priced the taps that are normally used to thread these, and even though I'm planning to build several lowers, I don't want to spend that much money. I finally just ordered a one foot length of 4140 prehard 1.25" solid round stock. I then turned one end to 1.125" and the other end to 1.188". I cut progressive steps in the stock, with each step 1/2" in length and .01" in greater diameter. I left the smaller end blank and then started cutting 16 tpi threads down the length of the stock, stopping when full thread depth had been reached.
I set it up in the mill vice and cut four flutes down the length of the whole thing then cut down 1/8" across four faces so I could use a 1" box wrench on the newly machined tap.

Did it work?
The pics of the second receiver I'm machining speak for themselves. It worked better than I thought it would, and I'm only out about 10 bucks.
There are times that having a mill and lathe come in real handy, and this was one of those times.


  1. Well, you definitely needs a new camera. :) So sapid metalwork, and so little details.

    1. Yeah, I did this post from my phone. The pictures were taken with my phone as well. Neither the pictures or the post came out like it was supposed to.
      I am not happy about it and may fix it later.

  2. If you had the lower on the lathe....why not single point the threads?

    1. Gungineer,

      Thanks for stopping by!
      Read the last sentence of the first paragraph. I did thread the first receiver, the one I had chucked in the 4 jaw, by single pointing it. I threaded a second receiver with the tap.
      I built the tap so I could drill and tap a receiver in the mill OR the lathe, depending on how I felt like doing it.

    2. More tools are always nice.

      It looks like you have a pretty nice jig setup in the lathe, but you have a point. If you have something in the lathe, but the mill is free, now you can use the mill istead of tearing down the lathe setup.

      Now how about showing us how you make a broach for that magwell ;-)

    3. The "jig" is just a piece of 1.25" square 6061 stock with two holes drilled in it.I guess were I to be a bit more ambitious, I would turn it to where the chucked end was round and on center with the buffer tube hole center, and could then be used with the 3 jaw chuck, making the process that much faster (nowhere near as much setup time needed).
      But, I'm just not that ambitious yet. =/

      Ah, the broach. I'm glad you mentioned that. I just happen to have something in the works that might be interesting to you. It is cheap, easy to use, and beats the heck out of using a file to clean up the corners of the mag well. I'll see if I can't get a post up about it soon, albeit with a few more construction pictures.

  3. There is just no substitute for a good mill and lathe. I need something bigger.

    1. Graybeard, I've seen the work you do with your mini mill and other tooling. You have nothing to be ashamed of, as you produce some great work with what you have.
      I've seen experienced gentlemen produce some of the nicest work on old Atlas, Logan, and Clausing equipment that I would have figured was ready for the scrap heap. It's not about how nice, new, or large your tooling is, but how you use it.

    2. Thanks for the kind words, but the work envelope is small. My lathe couldn't spin an entire receiver like you did to thread it.

      I need to build an addition onto my house to make a shop. Then I can get a big lathe and mill. Right now, I barely have the room for my small projects. I suppose I could give up woodworking and reclaim half the shop... nah.

    3. Size is a limiting factor, but in my case, experience is the biggest limiter. I'm not the most experienced machinist, and it has bit me in the tail a few times too many...

      I miss having an actual "shop". It's been a few years since I had that much room. Since I started building, I've only had a 2 car garage. I guess it's a good thing I sold my old CNC plasma machine I built, there's no way I could fit it in my garage with my mill and lathe.
      No sense in giving up the woodworking, that will be a valuable skill (and tooling) to have after the inevitable crash.