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Discussion Starter · #1 ·
I picked up two screw built recievers yesterday from as buddy of mine who was was going to trash them. The trunnion holes seem ok but the rails were screwed in. Screws and rails ar still intact.
My question is , can i spot weld these rails, then remove the screws and plug weld those hole without causing any distortion to the rails or the reciever? Should i remove the rails first and then plug weld and then spot weld the rails. Seems like a dumb question but I dont know if Plug welding will harden the metal and make it harder to spot weld.
 

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I would skip the spot welding. I assume there are least 2 screws per rail. Clamp one of the rails, remove one of the screws and plug weld from the outside. Remove the other screw on the rail and repeat. If the weld is proud on the outside, dress it down with a file.
 

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Discussion Starter · #3 ·
Sounds like a plan ! Thanks. Wasn't thinking that way but is more doable as it does both things at the same time. Fills the hole and secures the rail at the same time.
 

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You might want to use a aluminum or steel bar the inside width of the receiver (in the receiver) to prevent it from warping when welding up the holes.....
 

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When you go to plug weld them in, use a brass or copper backer. DO NOT put steel behind where you are welding.
elaboration , knowing why to do or not to do something goes a long way
 

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If you put steel behind where you are plug welding it would get welded as well. By using a copper or brass backer it will keep the weld from over penetrating and help prevent burning holes in the sheet metal. Not to mention, it acts as a heat sink. The backer also helps keep cleanup grinding on the inside to a minimum.
 

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If you put steel behind where you are plug welding it would get welded as well. By using a copper or brass backer it will keep the weld from over penetrating and help prevent burning holes in the sheet metal. Not to mention, it acts as a heat sink. The backer also helps keep cleanup grinding on the inside to a minimum.
What I failed to mention with using steel heat sink, is that the areas behind the holes to be welded needed to be relieved to prevent the receiver from being welded to the steel heat sink. A heat sink is necessary to prevent the warping of the receiver.
 

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Ive done this several times, on receivers 1.5mm & 1mm thick.
The trick is to cut & fit a small 3mm thick pure copper plate into the inside of the receiver.
Small squares plates of a few inches can be bought online for around $10. and you can reuse it several times.
1 cut plate will fit both sides normally. I found 3mm thick plate to be perfect. Dont use old pennies, they are not actually pure copper and not flat..jus sayn..
Clamp the plate into the receiver opposite of the hole.
I then take extra pr of welding gloves and slide or wrap 1 glove on each end of the receiver, exposing only the hole that needs welded up. The gloves just stop splatter over other areas.
I set this entire contraption in a vice, level it, then ground to the vice or expose a part of the top rail between gloves.
I then start my weld on an edge of the hole and drag it immediately to center, allowing it to pool up evenly. As it pools up, I will increase my feed standoff (pull back but continue to feed), until I finally can cut out. You want a real solid, centered pool of weld, so you dont have to go back and refill. Settings are pretty critical, typically I go for a faster feed, but a lower voltage setting than normal, YMMV, so is practice on scrap metal of similar thickness to dial it in.
What you will end up with a beautiful circular fill similar to a flattened rosebud with just a slight mushroom top. Distortion heat wont travel too far outside the immediate area as you can see and receiver is dead flat on the inside, if you do this right.
Allow the whole receiver to cool down to ambient, then do another hole, in series.
The excess on the outside of the receiver can then be ground down, until you can blend with a flap wheel, finally a hand file.
Yoda
310633
 

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If you put steel behind where you are plug welding it would get welded as well. By using a copper or brass backer it will keep the weld from over penetrating and help prevent burning holes in the sheet metal. Not to mention, it acts as a heat sink. The backer also helps keep cleanup grinding on the inside to a minimum.
thank you , im not a welder so i was curious
 

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Discussion Starter · #12 ·
Something i failed to notice was that the screws on the right hand side of one of these recievers the screw heads are ground flat to the receiver. To accommodate the safety lever i suppose.
I think I'm just going to remove the existing rails, plug weld with a copper backing and add new rails. That way I know the alignment is good. And if I fubar it, nothings lost but my time. I'm going to try and work on it today. Keep ya'll posted.
 
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