Repairing a machined aluminum upper

QYV

QYV

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Does anyone know what can be done to repair nicks and gouges in machined aluminum? The piece in question in the new upper for my XCR, which I got replaced on warranty by RobArm, which was subsequently damaged in transit by the CBSA. The damage is twofold: gouges/nicks in the outside, not to deep but a far cry from brand new condition and scrapes/cuts on the inside of the receiver from some kind of damage to the bolt carrier and ejector. The bolt carrier was literally stuck inside the receiver when I received it.

The CBSA is "investigating" the incident and seeing as replacement is not an option I need a repair estimate.
 
If you want it to look like NEW again, i think you'll have to completely strip the anodising off, and re-anodise it.... Not really easy or cheap. For deep gouges, you CAN weld aluminum, but its difficult, and you need to know an experianced welder to do it.

I havn't really done any refinishing, but it may be a hundred or a couple hundred bucks to have it re anodised, mabey more (it depends on who you get to do it)


If the CBSA damaged it, they should pay for the complete replacement or refinish of the upper (I would email RobArm and see how much they would charge for a refinish, to get a good estimate) or possibly email a refinisher.

If there is physical damage in to te rifle, then theres no way around it, it needs to be replaced, and since CBSA did the damage, they'll need to replace it!


I dont know how it'll work out, hopefully theres guys here who will be able to help you with how much refinishing should be.
 
(Ronin) said:
If it's 7075 like the lower is,forget welding.
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Yeah, the different grades all react differently. I've never had to have anything made of aluminum welded, but i heard it could be done...


In any case, the OP really shouldn't have had the problem in the first place :mad:

I guess thats why I always read people saying to package stuff up so overkill...
 
6061 welds just fine. A little trickier than mild steel but easy enough with a bit of practice.

7075 is not easy. Most welding shops will just tell you to F--- off.
 
Thanks for the input guys. I knew Al is tough to weld (my wife is a welder), I'll find out what kind of Al it is, though that may be proprietary information. What about the implication of welding it? Will it be brittle and/or weak in the welded area? Will it need to be heat treated again? Could it potential warp? What about dent/gouges that are to small to weld? Seems to me that there are a lot of things that could go wrong.

Believe me I wish I could just replace it, but no US export permit means replacement ain't an option. The only reason I got this new one was because it was a warranty replacement, so nothing 'new' crossed the border.
 
I would think the same rule would hold, nothing new is crossing the border. Since CBSA is responsible you should be able to send the existing upper back and receive a new one - there is no increase in the number of uppers in Canada - and CBSA should pay the bill both for shipping and for the upper which they destroyed.
 
QYV said:
What about the implication of welding it? Will it be brittle and/or weak in the welded area? Will it need to be heat treated again? Could it potential warp? What about dent/gouges that are to small to weld? Seems to me that there are a lot of things that could go wrong.
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The thing will be a bit of a dog's breakfast after welding. The weld deposit itself will have a slightly aged, as-cast structure (medium-high strength), the base metal immediately beside the fusion line will be wrought solution annealed (low strength), and the base metal a few millimeters away from the fusion line will be over-aged (med-low strength).

The best route for welding of any age-hardened aluminum is to solution anneal the whole part, make the repairs, then solution anneal again, then age harden. It goes without saying that this is also the most expensive way to do it.

If the nicks were small enough to be cosmetic only, you could probably repair it without worry, because the rest of the receiver will be strong enough to bear the load of a few weak points. But if the welds are deep and extensive, I think you have to go the route above.

My worry is that you say the bolt was actually trapped inside the receiver. If the receiver has been crushed to squeeze the bolt, then any attempt to force the receiver out into shape again is going to initiate cracking that will render your receiver useless.

To me, CBSA absolutely has to own up to destruction of this potentially irreplaceable item.
 
BattleRife said:
The thing will be a bit of a dog's breakfast after welding. The weld deposit itself will have a slightly aged, as-cast structure (medium-high strength), the base metal immediately beside the fusion line will be wrought solution annealed (low strength), and the base metal a few millimeters away from the fusion line will be over-aged (med-low strength).

The best route for welding of any age-hardened aluminum is to solution anneal the whole part, make the repairs, then solution anneal again, then age harden. It goes without saying that this is also the most expensive way to do it.

If the nicks were small enough to be cosmetic only, you could probably repair it without worry, because the rest of the receiver will be strong enough to bear the load of a few weak points. But if the welds are deep and extensive, I think you have to go the route above.
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Most of the marks are quite small. RA's recommendation was just to anodize over them not to weld, probably for a lot of the reasons you state above.

BattleRife said:
My worry is that you say the bolt was actually trapped inside the receiver. If the receiver has been crushed to squeeze the bolt, then any attempt to force the receiver out into shape again is going to initiate cracking that will render your receiver useless.

To me, CBSA absolutely has to own up to destruction of this potentially irreplaceable item.
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Agreed, I am not sure what the did to damage the inside, but it looks like it took enough of a hit to jam the ejector against the bolt carrier. After getting the it apart I was able to adjust the ejector so that it "runs". But between the scaring on the inside of the receiver and it ejecting in the wrong direction, there is definitely still something out of whack.
 
If you need a welder who can make really fine repair welds in aluminum ask around at automotive wheel repair shops. Some of those guys can work f#$%in' magic.
 
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