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Spot Welding Machine for question about welding aluminum bungs on pontoon boats

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Welding Automation for question about welding aluminum bungs on pontoon boats

Welding Automation for question about welding aluminum bungs on pontoon boats

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Platform Spot Welding Machine for question about welding aluminum bungs on pontoon boats

question about welding aluminum bungs on pontoon boats


Tue, 31 Aug 2021 15:36:30 GMT
Hi all,I recently welded a set of 1/2" bungs on a pair of aluminum pontoons.  I also welded a third one on a pontoon at the same time the only difference being that I didn't have a plug for that one so I welded it without a plug.  The first pair I welded in place with the plugs in place,  hand tight.Anyway,  I got a call from the client that the ones with the plugs were frozen solid in place as if they had been welded.  The one without the plug was fine when a plug was put into it.  These are aluminum plugs and bungs that I got from McMaster-Carr and they were designed to be welded on.Did welding these in place with the plugs in them, cause them to seize up?  I have encountered this with stainless nuts and bolts over the years and have since learned that if I weld stainless nuts and bolts in place, to separate them immediately before they cool down so as to prevent them from seizing up.  Same with aluminum?I am going to the client's place tomorrow morning to drill out and retap the holes in the bungs.  Needless to say, I am somewhat embarrassed.Thanks for your opinions,Tony
Reply:So tomorrow you are going to go tap your customers bung holes?  I can understand why you might be embarrassed, to admit this publicly. But then this is the internet and people post  up all sorts of strange things...  Sorry I couldn't resist...The bung shrank when welded.  1/2" NPT threads are tapered. So if the hole shrinks, it won't effect the fit like it would with a standard straight thread. That's why the one that wasn't installed still "fit". The hole got smaller, but the tapered thread still went in easy and sealed. The other ones became an interference fit just like as if you'd shrank a bearing on a shaft..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Originally Posted by DSWSo tomorrow you are going to go tap your customers bung holes?  I can understand why you might be embarrassed, to admit this publicly. But then this is the internet and people post  up all sorts of strange things...  Sorry I couldn't resist....
Reply:Originally Posted by therreraHi all,I recently welded a set of 1/2" bungs on a pair of aluminum pontoons.  I also welded a third one on a pontoon at the same time the only difference being that I didn't have a plug for that one so I welded it without a plug.  The first pair I welded in place with the plugs in place,  hand tight.Anyway,  I got a call from the client that the ones with the plugs were frozen solid in place as if they had been welded.  The one without the plug was fine when a plug was put into it.  These are aluminum plugs and bungs that I got from McMaster-Carr and they were designed to be welded on.Did welding these in place with the plugs in them, cause them to seize up?  I have encountered this with stainless nuts and bolts over the years and have since learned that if I weld stainless nuts and bolts in place, to separate them immediately before they cool down so as to prevent them from seizing up.  Same with aluminum?I am going to the client's place tomorrow morning to drill out and retap the holes in the bungs.  Needless to say, I am somewhat embarrassed.Thanks for your opinions,Tony
Reply:I've had good luck with putting a steel bolt, with a heavy coating of anti-seize, in the fitting before welding it in place.  Never had a problem with the fittings distorting, or with removing the bolt after welding.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:I strongly suggest installing stainless steel plugs ...  preferably with a hex head.  If you have any corrosion, the aluminum plugs will need drilled out again.  Even stainless might be difficult to remove, and a hex head will not round off/out as easily as a hex socket.Dynasty 300DXSmith He/Ar gas mixerMM350PHobart Handler 120Smith LW7, MW5, AW1A
Reply:Before I drilled out anything I'd first try to heat the bung. A little Kroil wouldn't hurt either.
Reply:If the plugs were overly tighten they could seize up and you cant remove them.
Reply:Hi all,I hadn't received notice that there were more replies.  I came on to post another request for help and decided to check this thread.  I appreciate the advice and will incorporate it into my routine when welding these things in place again.I found out exactly what Dave P was saying after I tapped the new threads I saw they looked all galled up.  I put more oil on the tap and ran it through again and they smoothed out.  I will go with the steel or stainless steel plug approach and anti-sieze as a preventive measure in the future.It never occurred to me to heat the damn things before drilling them out.   I should have at least tried before going through the drill and tap routine.I will be posting a new thread under mechanical / auto body repair for a new project that I have taken on involving thin sheet metal and forming.Thanks guys,TonyLast edited by therrera; 02-22-2013 at 09:20 PM.Reason: for more clarity..

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