1963 Vox AC-4 with stripped bolt

[christarak]

I am trying to get to "square one" on this vintage AC4, but I can't even get the chassis out. Some gorilla has stripped the threads on the two bolts that hold the chassis in the cabinet. Turning the nut just spins the bolt in the wooden cab. I am hoping to get two peices of advice:
1. How do I remove the bolt, nut, and chassis?
2. After the repair, how should I reattach the chassis? I can only think of drilling a hole through the top of the cabinet which would mightlily piss off the owner. Wood screws would not support the weight of the chassis with transformers.
Any advice is much appreciated...even warm words of sympathy are good.

(The fault: The amp trips the house circuit breaker on power up with power through bulb current limiter)

[Jon Snell]

Does the chassis have to be removed?
If it trips an earth leakage breaker/trip then it may be something basic, like a silly and dangerous death cap.
If the chassis must be removed, put that to the owner and get permision the attempt a removal of the fixing nuts with a view to total removal and replacement with a cheese headed new screw in a cup through the woodwork and securing the chassis once again.
Be mindful of the covering, it easily rips if you are not carefull.
You cannot drill the old bolt out! you must remove it from the outside.

[Pixel]

Near the end of the bolt put two nuts on the exposed thread and tighten them against each other. Holding those you should be able to turn the other nut.

Reversing this procedure should let you reattach the chassis when the time comes.

[christarak]

Does the chassis have to be removed?
You cannot drill the old bolt out! you must remove it from the outside.

Thanks Jon. I'm not sure what you mean by "remove it from the outside". Do you mean drill through the outside tolex then through the wood and hope to find the top of the bolt? I can't feel the bolt moving through the tolex when I wiggle it from inside.

I will start fault-finding with the chassis in place, but it's quite loose. I might try to secure the chassis using the double-nut method suggested by Pixel.

[seven]

Yeah, JMI and their cab makers did that back then, they recessed the screws and covered over in vynhyde... kind of a pain when threads get bunged up. Pixel's got it.

[christarak]

Near the end of the bolt put two nuts on the exposed thread and tighten them against each other. Holding those you should be able to turn the other nut.

Reversing this procedure should let you reattach the chassis when the time comes.

Thanks for taking the time to offer support, Pixel. I'll give that a go but it looks like monkey-boy crushed the threads with pliers.

[christarak]

Yeah, JMI and their cab makers did that back then, they recessed the screws and covered over in vynhyde.

Thank you Seven

[Chuck H]

...but it looks like monkey-boy crushed the threads with pliers.

Well I do lose patience when someone else does something like this and it falls on me to fix it. What "I" would do is like Pixel said. If the nuts don't hold tight enough and it didn't work I would crush the threads again like monkey boy and turn the nut at the chassis. If the threads are already bunged that's not your fault. I've even taken it so far as to use a Dremel to saw a slot at the end of a bolt so I could hold its rotation with a screw driver. Or file small flats at the end of the bolt so I had something secure to hold with pliers. That said, I've also found myself against a wall for options when nothing works or my ham handed impatience makes things worse than they were already. So try to keep a cool head I guess.

[Mick Bailey]

I would very carefully Dremel through the nut to remove it in two pieces without damage to the bolt. Then remove the chassis and grip the bolt with slim mole-grips or pliers using a strip of copper folded into a U shape to protect the threads. Then run a die down the threads as far as the pliers, then change over to finish off the full length. It's probably a BA thread and a split die can be opened up with a little brass wedge driven in. Not too much or the die will break, but it makes the first-pass easier. If necessary remove the wedge and run the die down again. It should clean up with just finger pressure. I wouldn't remove the bolt - wicking decent superglue around it will lock it into position and a cleaned-up thread will mean the replacement nut will go on easily.

[Chuck H]

I would very carefully Dremel through the nut to remove it in two pieces without damage to the bolt. Then remove the chassis and grip the bolt with slim mole-grips or pliers using a strip of copper folded into a U shape to protect the threads. Then run a die down the threads as far as the pliers, then change over to finish off the full length. It's probably a BA thread and a split die can be opened up with a little brass wedge driven in. Not too much or the die will break, but it makes the first-pass easier. If necessary remove the wedge and run the die down again. It should clean up with just finger pressure. I wouldn't remove the bolt - wicking decent superglue around it will lock it into position and a cleaned-up thread will mean the replacement nut will go on easily.

Well this is certainly a Mick fix. Nothing but class here. And certainly the BEST way to do it. Mick is a guy that's fixed a lot of different stuff and I always learn something reading his posts. So taking a tip from this I have an idea for a stripped down version that should work fine and might be easier to do for someone that may not own every tool known to man

Since the thread is plenty long for the application I would skip the step of trying to cut the nut with a Dremel. Mostly because I don't know of a Dremel attachment that could do such a job without damaging either the bolt or the chassis. So instead I would crimp some ViceGrip type pliers on the end of the bolt to hold it while loostening the nut. Use a Dremel to cut off the very end of the bolt that you crushed with the ViceGrip. Remove the chassis and restore the remaining threads as best you can using a die as Mick suggested. If you don't have a die rig or one that fits well in the tight space you could use a higher grade nut turned over the bolt to reshape the threads. The harder steel nut should be able to do this and you have to be careful not to cross thread (I actually have done this and it works). Then correct the stripping at the cabinet with super glue as Mick suggested (brilliant!). And you should be good to go with a bolt sticking down about 1/8" shorter than it was.

[Pixel]

Compared to the other hardware in there the bolt in question just looks out of place. Maybe the gorilla put the wrong mounting hardware in.

Once you get the chassis out if the tolex is cooperative you could peel it back a little and see what you are dealing with there.

[christarak]

I would very carefully Dremel through the nut to remove it in two pieces without damage to the bolt. Then remove the chassis and grip the bolt with slim mole-grips or pliers using a strip of copper folded into a U shape to protect the threads. Then run a die down the threads as far as the pliers, then change over to finish off the full length. It's probably a BA thread and a split die can be opened up with a little brass wedge driven in.

Wow. That's way more class than I have Mick. I can foresee myself being rushed to the operating theatre to have a dremel bit removed from my eye and a split die splitting my cheek open. I like the superglue die method enough to head down to the hardware store this morning.

[christarak]

I would crimp some ViceGrip type pliers on the end of the bolt to hold it while loosening the nut. Use a Dremel to cut off the very end of the bolt that you crushed with the ViceGrip. Remove the chassis and restore the remaining threads as best you can using a die as Mick suggested. If you don't have a die rig or one that fits well in the tight space you could use a higher grade nut turned over the bolt to reshape the threads. The harder steel nut should be able to do this and you have to be careful not to cross thread (I actually have done this and it works). Then correct the stripping at the cabinet with super glue as Mick suggested (brilliant!). And you should be good to go with a bolt sticking down about 1/8" shorter than it was.

I agree that Mick's suggestion would be better, but I don't have the skillset to tackle that. I suspect gorilla Tech before me has tried a similar approach because the other stripped mounting bolt is shorter than the one I photographed. It's a trip to the hardware store for me. Thank you Chuck. Thanks Mick.

[Jon Snell]

The original fixings are BA sized and it looks like a UNF nut has been forced on to the stud.
Hold the end of the stud (not the woodwork end) with a pair of grips/pliers and slacken the nut as far as you can towards the pliers.
Cut the stud with a Dremel or small hacksaw up against the nut. That will leave you enough thread to fix a new nut on when putting the chassis back in.
If the nut won't budge, use a Dremel to cut through the nut, at an angle and split the nut.

[Chuck H]

The original fixings are BA sized and it looks like a UNF nut has been forced on to the stud.

Wow lets hope not! But close up the threads do look pretty beat. Only christarak will know for sure after attempting to remove that nut. But if the threads can't be saved there's not much choice but to try and peel back the covering (vinyl? Tolex?). That or dig the screw through the wood and do an epoxy repair with a new screw in place.