Welding G-clamp

[Turbo]

I got this clamp as part of a job lot but the thread boss has a crack in it.

The crack goes all way through to the inside but there is still part of the boss on the left not cracked yet. The clamp is a record 121-3" made from drop forged steel.

So any ideas what to do with this?

I have mig and mma with 6013 and dissimilar/special metals rods available. I was thinking of doing a few runs of dissimilar rod along the crack to stop the crack opening up.

I don't have a suitable tap to clean up the threads so I have to be careful not to penetrate too far. The outside dia of the thread is 0.490" and it's very slightly finer than 12 tpi according to my ww thread pitch gauge but a 1/2" ww tap wont fit. Any idea what the thread is?

 

[doubleboost]

It has a good chance to be a "acme" thread
Put a good reinforcing run of dissimilar metal over the crack
Strange for a steel forging to crack like that

 

[brightspark]

abuse more than likely

 

[Bill Edwards]

As doubleboost says really - good chance it'll be acme thread, and build it up with dissimilar rod. Though I have done that kind of job with MIG as well, but dissimilar is probably the correct choice.
Rather than risk burning through, put plenty of runs on top - looks probably don't matter here, and strength does.
And like brightspark says, probably caused by abuse!

 

[Turbo]

Thanks for the advice guys.

If it is an acme thread it's not a standard one. 1/2" acme thread is 10tpi not 12tpi.

Anyway, I'll post a pic if the results.

 

[Turbo]

Got the clamp welded using a 2.5mm dissimilar metals rod.

After some tidying with the grinder it turned out ok. Clamp is being painted now, soon be as good as new.

 

[Kent]

Just be careful what you do with it now

 

[wheresmejumper]

I would have left the reinforcement of the bead there,not grind it all off

 

[Sarto]

Hi.
Easy question: whydo you prefer dissimilar metal rods, if in the end it is steel?

SARTo

 

[sardine]

The problem I find with old G clamps is the pad on the end of the screw is often missing. If I had a lathe it would be a simple job to make them, but I don't. ( yet )

 

[Pete.]

Does the screw still run through the forging? It's not uncommon for welding like that to tighten up the thread.

 

[Kent]

The problem I find with old G clamps is the pad on the end of the screw is often missing. If I had a lathe it would be a simple job to make them, but I don't. ( yet )

I like to have a few with the foot missing. Sometimes it's a pain in itself others a bonus

 

[Richard.]

I would have left the reinforcement of the bead there,not grind it all off

I would of done the same thing. The added reinforcement ain't gonna look as nice as a nicely blended item but it's a G clamp and a little extra weld metal may prove to add a little extra strength in this case.

 

[Turbo]

I would have left the reinforcement of the bead there,not grind it all off

I built up several beads across the cracked area as it wasn't a straight crack. Even though I ground off the top of the beads the bulk of the bead is still there and the clamp boss is significantly thicker where the crack was.

Does the screw still run through the forging? It's not uncommon for welding like that to tighten up the thread.

The screw is a loose fit in the forging and there was never any fear of it tightening up after welding.

 

[ross1993]

Hi.
Easy question: whydo you prefer dissimilar metal rods, if in the end it is steel?

SARTo

can anybody explain this to me too ?

 

[Bill Edwards]

Hi.
Easy question: whydo you prefer dissimilar metal rods, if in the end it is steel?

SARTo

can anybody explain this to me too ?

Although the metal will be more or less steel, it's impossible to know the exact composition of it and it may not take to welding very well.
A dissimilar rod is the perfect choice where the steel may not be good to weld, or when you don't know the composition of it. They're also very, very strong.

 

[Turbo]

A dissimilar rod is the perfect choice where the steel may not be good to weld, or when you don't know the composition of it. They're also very, very strong.

As he said.

They've got to be the easiest rod I've ever used for welding, it's a pity they're so expensive. I've also used them for cast iron, so they're very versatile and useful to keep in the cupboard. They also form quite a hard compound after welding so you need to take care if you need to drill or machine afterwards.

 

[ross1993]

Say I had to weld s g clamp like the beginning of this thread , would i use 308 or 312 ? Or does it not matter

 

[Kent]

I have never used dis-similar rods on such a thing but have done plenty with low hydrogen or 6013 and std mig wire
Some such tools are still in service 30 yrs on
A new g clamp isn't mega bucks so it's pretty much minium time min cost or a trip to the scrap bin
I shouldn't then use such s thing in a situation it might add to the risks. Just not worth it

 

[ross1993]

in my position id have bought a new g clamp , i dont have the money for rods like that . just wondered why people seemed to use them on things other than dissimilar welds