Weld Questions On My Receiver

[Bil]

That could work,if you are pleased with the alignment.I did one like this,but when I attached the front I noticed a 'sweep' to the gun not readily noticable on just the rear section.I hadn't completely finished the rear welds so could fix it.But you look like you are being more careful than I was at first! ---bil

[Gorbachov]

I like that comparison of being able to hold the piece by hand and checking the alignment by rotating it like a chicken on a spit. Great analogy! I was able to get the rear section set up for welding last weekend and have attached a picture.

You'll see I've got a .02" copper sleeve I made that's held in place by the copper straps that tightly surround the inside of the cut, but my TIG welding buddy tells me it's way too thin and the heat from the welder will blow right through it.

I’m thinking of machining a solid copper block to fit tight inside the receiver that I’ll make in two pieces screwed together so I can remove it. This will be a permanent fixture I could hopefully reuse on my next build. Any thought on this?

The variable speed control on my mini mill/drill machine went out a couple weeks ago so I went down to Harbor Freight and bought a multi-machine combination mill/lathe that I’ve attached pictures of and I’m thinking I’ll break it in on the block.

[gdmoore28]

The variable speed control on my mini mill/drill machine went out a couple weeks ago so I went down to Harbor Freight and bought a multi-machine combination mill/lathe that I’ve attached pictures of and I’m thinking I’ll break it in on the block.

Rear Receiver Section II.jpg

Hi Gorby,
I've put aside enough cash to buy one of the HF Mill/Drill setups like you have to equip my new shop. I'd be very interested in your opinion on the machine, and the various attachments you will be using in your SA build. I have zero experience with a mill, so your exepriences and suggestions would be most appreciated.

Will be following your build with great interest.

GeeDeeEmm

[Gorbachov]

GeeDeeEmm:

Like you I’m a real novice when it comes to using a mill or metal lathe. I’ve always been interested in learning how to use them and just for fun several years ago I took an evening six week machine tool course at a local junior college. Having never used what I learned I’m not 100% sure it’s all going to come back to me. I think the biggest learning curve is going to be figuring out what tooling I’m going to need.

Harbor Freight has a multiple piece set of end mills that range in size from about .060" to .500” that come in a really nice wood box and sell for $75 which I’m going to pick up tomorrow. I'm also going to buy a good selection of ball end mills, probably through one of my tool catalogs, because Harbor Freight doesn’t have them. I’m not as up to speed on the necessary lathe tools I’m going to need, but I’ll figure that out as I attempt different projects.

The machine I bought is made by Central Machinery and called a “Multipurpose Machine” Model #5980. It was a floor display at Harbor Freight and I don’t see this particular one listed in their online product offering, which leads me to think it may have been replaced by a newer model listed as ITEM 46199-6VGA. The quality is what is to be expected of a Chinese made piece of equipment, which is lacking some in fit and finish.

So far the only real issue I have with it is the milling machine head does not have a primary vertical adjustment and no way of bringing the chuck close to the work area, as the work table is fixed vertically and designed to hold the tool post for the lathe and only adjusts 0/90 degrees horizontally. There is a fine adjustment on the spindle with about 6” of vertical travel that has a graduating indicator in .005” increments and this may be all I need.

The other feature that will take some getting used to is not having a variable speed adjustment that operates by turning a knob, which my mini mill/drill machine did have. Both the speed adjustments on the mill and the lathe are done by changing the location of the drive belt on the pulleys, similar to what you’d have on a drill press. I can live with this, but it was nice to be able to dial in just the right speed with a knob without fooling with belts.

Gorbachov (aka Jerry)

[Gorbachov]

I finally got around to welding up the section of the receiver behind the trunnion as you can see by the attached pictures and I’m pretty happy with the way it turned out. All the surfaces are really flush with each other and I don’t see any warpage or misalignment of the two sections.

Now that I have this section done I’m going to reference the alignment of the other sections off this piece, but I’d like to understand one measurement before I go any further. Does the back edge of the small rear piece measure 3” from dead center of the rear rivet hole of the rail?

There are good pictures in the stickys of the other dimensions and I think I’m good to go on those. I do have aother question though and that is whether it’s just as critical to back up the other welds with copper as I did this 1st weld? If you all could help me on this I’d really appreciate it.

[gdmoore28]

Looks good, Jerry --

Hope you make a habit of keeping us posted with good pics and text. It's been a while since somebody has done this, so it would be nice to follow along again. Gives us all a chance to feel "in" on your build.

GeeDeeEmm

[Bil]

I have 2.85 on two receivers,one being a BRP repro.An easier way of making sure is to put the camming piece on your receiver front,it looks like you have enough to do that.Then install the topcover and check for fit.This should give you an idea of the length and also straightness.I run pieces of steel and copper to clamp to.It is also important to make sure the rear piece is square to the rest of the receiver,both up and down,and side to side.Being off here results in the buffer being out of line,and problems with the spring.It isn't as hard as it may sound.Your job looks good so far-nice work!.And I would use the copper on the welds,it helps keep them from 'sagging',and makes it easier to clean up afterwards.It is not as important on the barrel bearing weld if you have the older type de-mil. ---bil

[Gorbachov]

After posting these picture I got to taking a look at the one titled “Welded Rear Receiver 2” and it appeared from the picture that the two sections were not parallel with each other, so I used a straightedge to check this and found that they were in fact off, as you can see in the picture I’ve attached with red lines.

This is very disappointing and I’m going to clean up the welds on the outside and cut them apart again for re-welding. I had mentioned in an earlier post that I was going to machine a copper block to extend through both sections and I didn’t do that and used the copper flat stock as seen in my earlier pictures.

What I don’t understand is the holes in both pieces of flat stock were lined up perfectly with the holes in the rails, which I used as a template and it should have corrected this. I think if I machine a very tight fitting block that extends well into both sections it should keep it very square and I can reuse the block.

I’ve read in some other posts where guys had to cut and re-weld sections so I guess I shouldn’t feel to bad, but the perfectionist in me sure doesn’t like the idea of having to redo things and it’s even more difficult to admit mistakes. I’ve got to remind myself that this isn’t a contest and it’s all just for fun!

I ultimately want to build a second gun and mount them on a twin anti-aircraft pedestal and if this block concept works I should be able to be reused on a second build. I’ll keep you all posted on my re-weld and will hopefully have some good pictures in a few weeks of my block and how the concept works out.

[Bil]

I thought it looked off in pic3,but figured it was the camera angle.When I did mine,I used correr strips ,but I also used 3 1/16 steel flat stock inside.I fit it do cover the entire flat where the rails go-each side is differant.Then I made the copper the same,clamped both in place,and cheched alignment using the rails.Then I drilled through the holes,into the copper and through the flat stock,bolted it inside and welded.The copper alone wouldn,t keep it straight,and the clamps would slip from the heating and cooling.Bolting it held nicely.Also,I didn't get as much welding done before checking,it is easier to cut a few spots than an entire seam.I still had to cut and adjust to get it right.Keep at it,it looks good! ---bil

[TbcSEOD]

Sorry to hear it pulled to the side - my guess is that was the "last side" welded - if so it would stand to reason that to much heat got into the metal and expanded it - once it cooled it "pulled" the other side over.

A few years ago I read a scientific study on welding and the forces that are generated inside the metal and it is on the scale of the forces released in a earthquake (as I recall) its just on a much smaller area.

By chance how long were your "sections of weld" and what kind of amps did you use? The weld looks really great thats why I am asking.

~T

[TbcSEOD]

oh, and if you don't mind me asking what size/type rod did you use for fill?

Thanks,
~T