Stuck Bolts in Dissimilar Metal

[Shark Bait]

I have somewhat of a unique situation I need some help with. My (soon to be ex-) wife's longarm sewing table is aluminum beams and legs that are bolted together with steel Allen head bolts. We need to take it apart because, with the divorce, we are selling the house and moving. For lack of a better term, the bolts are "captured". They are inserted through the inner wall of the beam and bolt into threaded holes in the legs. The only way to tighten or loosen the bolts is to feed the Allen wrench through the hole in the outer wall of the beam. 4.5mm seems to be the right size for the Allen bolt heads. For the bolts we can get the wrench in to, we can loosen the bolts some, but then they bind like a rusty bolt. Sounds familiar? LOL. Some of the bolts we can't even get the wrench on the head. We think maybe the holes in the legs weren't quite true when they were drilled and tapped, just enough to prevent the wrench from inserting into the hole on the top of the bolts. They could be a different size hole in the head, but that's doubtful. There is at least 1 bolt like that on 3 of the legs. I put some PB Blaster on them, which didn't help right away. I'll be back over there in a couple of days to work on it again. We've sort of settled on drilling the heads off through the holes in the beams. We need to do this because the beams are 12 feet long and we need to take this thing apart to get it out of the basement. At some point in time she will want to re-assemble the table or sell it, So it would be nice to be able to remove all the bolts. Does anyone have any ideas? Or do any of you think you could fix this? I am hoping to avoid drilling them all the way out and re-tapping because there is only so much room in these beams. Might have to do some extra work to use different sized bolts. Maybe another piece of metal could be welded to the bolt heads. Then would heat work in this case to try and back them out? Any help would be appreciated.

 

[Corbet]

First report back after you see what the PB does. I’m guessing that will free them up. If not please take some photos of the bolts/legs. I’d also take some SAE Allen keys in case they are not actually metric. Based on your verbal description would cutting or modifying an Allen key help with access?

The next time the table gets assembled I’d use grease or anti-seize on these bolts.

 

[DaveInDenver]

What @Corbet says. Dissimilar metals in a humid environment like a basement is textbook galvanic corrosion. When this happens on bicycles, usually a seat post will corrode itself into a steel frame for example, the outcome is usually to sacrifice the aluminum to save the steel.

 

[BritKLR]

Here's one from the "Stitch Bitch".......I've assembled and disassembled countless sewing machine tables but I'm not familiar with what you're describing. Is it a quilting table? If so, google the type of sewing/table and there will be a Forum that supports it and post your question there. I suspect someone else has had to deal with a similar problem

Goodluck!

 

[Shark Bait]

Thanks, guys. The ones we can get the Allen wrench into are definitely 4.5mm. So, they all should be. Yes. If cut a longer 4.5 Allen wrench and put it in a drill I could try that, now that the PB Blaster has been sitting on it. Might even run over there today and/or tomorrow and spray some more on it. It IS a quilting table. I can't remember the make, but I will find out. That's a good idea to check their forums. I will get some pictures. If I can get some of them out then it will be less work later extracting headless bolts.

 

[Inukshuk]

If you decide to drill, try easy-outs first? On an electric drill or 3/8 low-torque impact drill? They might grab that allen head and do the trick

 

[Shark Bait]

If you decide to drill, try easy-outs first? On an electric drill or 3/8 low-torque impact drill? They might grab that allen head and do the trick

Yeah. It is a really tight space. I would not be able to get anything much bigger than 1/4 inch through the hole to the bolt head.

 

[Pz10420]

If you have a set of torx bits I would take them with you as well. Quite often they can be tapped into a crappy allen head drive and will grab better than the allen keys. A 4.5mm allen head is reallllly uncommon.

 

[Shark Bait]

Here is what I am dealing with. I seem to be able to get the Allen wrench in the top bolts on 3 of the legs. I can start the bolt out, but the top of the beam pushes away from the leg. I suppose I could smack the top of the beam with a BFH and try to get it back flush with the leg. Maybe that is why those are binding. I tried drilling one bolt head. Maybe my drill bit is dull, IDK. What makes it tough is, you can't see the bolt head. Wonder if heating the area with a torch would help. I'm going to search for a repair shop and see if I can find anyone with experience. I found this video, and it is rather hilarious. The guy gets to the spot we did and has the same problem. Fast forward to about 25:00 minutes.
View: https://www.youtube.com/watch?v=ibVz1-mkVg4
All of a sudden the table is completely apart and he grumbles about having to wrestle with it a little. LOL

 

[DaveInDenver]

That's known as T-slot struts but they're not using the various hardware, which is the real genius of the stuff. The joint is kind of awkward.

Kind of looks to me like if you strip that bolt it won't matter. Maybe you could just slide an insert in here.



Or maybe orient the corner the way the t-slot is supposed to work with the corner angles? That might not be possible depending on how they cut the struts, though.