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Discussion Starter · #1 ·
A couple questions; I have a few milled kits, at least one or two are getting sent to Turbo for his excellent work. I'd like to tackle one myself, either a semi BREN or semi SG43 build possibly, just so I can say I accomplished it. So here's the deal:

1) Equipment: I currently have a Lincoln 140C 120V MIG, and am upgrading to a Lincoln 180 230V MIG in the very near future. I use 25/75 shielding gas, and the 180 is rated at "1/2 inch mild steel". Is this adequate for re-welding a build?

2) Process: The torch cuts left swaths of material missing from the receiver, around 1/6 of an inch or so. Correct me if I'm wrong, but I would imagine the process goes something like this: Clean up the chunks so that all the slag is removed from the internals so that the parts will be free to move. Make multiple weld passes on the torch cuts to re-build the areas that are missing. Grind and file them to fit up cleanly, especially internally. Fit a jig to the parts to hold them in proper relation to each other and keep them from warping from the heat during the re-joining process. Re-weld. Grind and file the welds on the outside to match the lines of the original.

Something like this?


If so, is it best to use .25, .30, or .35 wire to build up the areas that the torch cut out? If using a good jig, should I still use some Hylo Cool or some such to help with the heat? I assume there is no way to weld the internal seams due to the tight space, so building up the cuts, and grinding/filing it internally prior to re welding is the only way right? The semi blocking bar and mods to the working parts can be done prior to re-welding of course. What else should I consider in this? Thanks!
 

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Discussion Starter · #3 ·
So if the gap is less than 1/4 inch, I dont need to build it up prior to rewelding and clean up the inside? Can this be done after rewelding with a dremel tool provided there is clearance? Also will the MIG 140C handle this or should I wait till I have my 180?
 

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whenever i get to my semi RPD kit i have two sets of RPD recivers sitting around... i'm thinking of cleaning up the cuts on one and using the other set of bits to offset and fill in the gaps where applicable... depends how wide the torch cuts are.. and after that, welding it all together with whatever semi mods being welded in too...
 

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This type of work where you have no fitup, or very poor fitup is where those that can develope a feel for the flow of the metal set themselves apart. Some practice on scrap of the same gauge thickness will give you a chance to try different technique, and remember to breath and relax.
 

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Your welder power is fine paritcularily with good technique and prep. .030 wire size is good all the way around. I find my weld materiel is quite a bit harder than the stubs or barrels I have welded. you need to be fairly experienced at welding gaps. Some receivers torch cuts are worse than others and you may need filler material. Each receiver you repair will need diffrent technique to repair it, depending on lots of variables. I find a needle scaler works pretty awesome for slag removal. I need to finish up my amd 65 then its off to something more complicated, ppsh or dp28 we will what I start on!
 

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floridadon said:
This type of work where you have no fitup, or very poor fitup is where those that can develope a feel for the flow of the metal set themselves apart. Some practice on scrap of the same gauge thickness will give you a chance to try different technique, and remember to breath and relax.

+1

Definitely practice with some scrap, this'll help you figure out settings especially for cold-starts. Small wire will help, lots easier to manipulate but don't go overboard with the gap size.

t
 

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Use copper (flashing or take a 1" copper pipe coupling from the hardware store, cut it open and hammer it flat!) backers to help hold the weld/filler in the weld. Makes final clean-up and grinding MUCH faster. Also acts as a heat sink. Your parts WILL warp and move unless you bolt them down and secure them rock solid to some form of a jig. Weld SMALL sections about 1/2 or less at a time, then move to the opposite side and weld. That way you don't build up enough heat to cause major warping in any one area. Go SLOW
 
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