Welding a nut on to a rounded bolt - problem

[jammy_basturd]

Got a socket head bolt sitting in a recess in a brake caliper (its one of the mounting bolts). Tried to weld a nut on to the bolt several times (the first time filled the 'socket' in the bolt with weld, so now I'm effectively welding the nut on to weld). But everytime the nut just comes straight off, seemingly the weld just isn't getting any penetration at all.

Any ideas of what the problem might be? The actual welding process seems to go fine, a good noise, good constant weld, etc. I am thinking that possibly the earth isn't quite good enough, or maybe because I'm welding inside the nut, something funny is happening with the gas?

I'm leaving it about 10-15 minutes to cool, long enough?

Its a 150T Mig welder btw.

 

[Mattl]

You will need both parts to be as clean as possible and crank the power right up and blast it. Should be good to go as soon as its cooled from the red hot stage, no real need to wait 15 mins. Make sure you aim the torch at a decent angle to ensure good penetration of both parts.

 

[Porschemaniac]

I had this problem many years ago, trying to get a broken exhaust stud out of an old NSR125 (I did say it was some time ago!!!)

What I (eventually) found was that whilst I was getting OK penetration on the head of the bolt, the same was not true for the nut. Conseqeuntly, the 'weld' gave up easily when you applied even the smallest amount of weld.

At the time, I was using a SIP Handymate 90 amp gassless. I found that the solution was to up the power (to full whack on this welder) and try using a slightly longer length of wire from the torch - to allow the shallowest angle possible - to try and get some penetration on the nut. Being gassless, there was no issue with the wire extending beyond a gas shorud!

It did work, but it was a PITA to do.

Presumably the bolt is siezed? Any chance of drilling and getting a good easy-out in there?

Cheers,

Ian.

 

[wyn]

Sometimes welding a washer on first helps as you can then be sure you have welded it to the bolt. Then stick the nut to the washer inside and out.
Maybe don't let it cool as long.

 

[^neo^]

is it a VW by any chance?

 

[jammy_basturd]

Its on a TVR.

I don't have great access really, its on the back caliper, so I can't turn the hub to get better access either.

I don't have room to weld the nut on the outside, so its has to be on the inside. The lack of access and welding the inside of the nut also means I'm welding pretty much at 90 degrees!

Will try whacking up the power (almost there already now), and welding a bit further away.

I don't think the bolt is seized, think its just been rounded after been undone/done up a few times with ill-fitting tools. Only just have access to weld, so I don't think drilling is an option. Will give it a go again tomorrow, think I'll try and improve the earth too. If all else fails I'll whack out the grinder and go through the spacer block.

 

[alistairlee]

You could try and hammer on a smaller socket metric for imperial or vice-versa.
Failing that a small chisel and hammer and tap it round?

Regards
Al

 

[gordon stephenson]

Sometimes welding a washer on first helps as you can then be sure you have welded it to the bolt. Then stick the nut to the washer inside and out.
Maybe don't let it cool as long.

Exect as I described to someone in a thread a few weeks ago. Had many a success story using this method.
Cheers Gordon.

 

[^neo^]

Is it the caliper slider bolt, or the carrier bolt?
If it's the slider bolt, in the past i have cut the ears off the pads so they fall out, removed the disc, and then slid the caliper off the slider. Then you're left with the bolts stuck in the carrier, but at least you can get to them to work on!
This may even work if it is the carrier bolts, as when the disc is off you should be able to drill them out from the front

 

[kiall1987]

Clean it really good weld the nut on at higher amp than you would normally would , then allow to cool from glowing red then strike it square on with a punch and give it a go then

 

[jammy_basturd]

It's an alloy caliper that's radially mounted.

Tried again tonight, cleaned up the earth, managed to pull all the old weld out and then weld in a bolt which seemed to have welded a whole lot better. Then the head snapped off the bolt. So welded a big thick washer on to the end of the snapped bolt (now I could weld clear off the recess in the caliper), then welded a nut to the end of that. The bolt snapped again.

At this point I decided just to grind through the spacer and bolt shank behind the caliper body. Not much room so could only use the grinder for half of it, and after that had to use a hacksaw, but it all came free in the end. Don't think the caliper bolt was seized either, since the bolt head came out of the caliper fine, and the remnants of the bolt came out of the hub relatively easy with some mole grips.

Anyway, thanks for all your help.