Rusnok repair/ material specs for welding

ddayan · Jul 3, 2020

Hello,

I have a Rusnok head with a cracked over arm clamp. The welder told me the part needs to be heat treated before it can be repaired. He mentioned the heat treatment is very specific to the material.

He also said cast iron is not worth trying to weld.

Any thoughts on what this part is made of? or maybe any helpful tips for heat treatments?

The thought also crossed my mind that heat treating may affect the tolerances of the machined side?

Limy Sami · Jul 3, 2020

I'll stay out of the welding debate, BUT

Before you let a welder anywhere near it, make an accurate as possible drawing of it, .....because after welder's buggered it up, getting accurate dims to make a replacement is nigh impossible.

mjk · Jul 3, 2020

"The thought also crossed my mind that heat treating may affect the tolerances of the machined side?"
YUP

2nd on creating a drawing.
If the heat treatment doesn't distort it the welding will

gbent · Jul 3, 2020

Looks to me like its already been welded, and it didn't work. If it was mine, I'd look hard at it before welding. I'd also figure the bore would need to be rebored.

Rob F. · Jul 3, 2020

I think the welder should have said it needs to pre-heated prior to welding it. The only hope of a weld repair working is the whole thing is preheated then welded and then the whole thing is then put back in the oven to cool down slowly. Were it mine I might be tempted to braze the broken piece back on and while at it braze a steel band to the outside that matches the shape.
Maybe easier to make a new one from a steel weldment though. Can you get heavy tube to make it from?

eKretz · Jul 3, 2020

Maybe the welder did say that and OP misunderstood. It is weldable, but it may distort like crazy. I recently welded an unobtainium cast iron wheel hub for a guy... After welding, a lot of the surfaces near the welded area had to be remachined.

For successful welding, cast iron absolutely needs to be preheated to 450°+ and held there during welding. Nickel rod works well. Welds need to be peened and then the whole thing needs to be slow cooled. Missing any of these steps could result in cracks after the part cools.

ddayan · Jul 6, 2020

It looks like the part was drilled and tapped through the center of the coupling on the broken side to compensate. I think i might get a 2 inch steel tube to use and drill a hole to fit it?

Limy Sami · Jul 6, 2020

ddayan said:
It looks like the part was drilled and tapped through the center of the coupling on the broken side to compensate. I think i might get a 2 inch steel tube to use and drill a hole to fit it?

Please stop and think about the entire job, in short, unless the two holes, (one - the overarm, the other the spindle, ) are at EXACTLY the correct centres, both in the same plane, and to the correct size, the part will not only be useless, but should it somehow fit the machine - is very likely to cause a lot of damage.
.

magneticanomaly · Jul 6, 2020

Welding of cast iron has been discussed to death here. Spend a couple of hours reading threads. It can be done very successfully, with joint prep, preheat, slow cool, 99% or 55% Nickel rod, SMAW: or braze-welding with oxyacetylene torch.

Your part is pretty simple. If preheat is limited to the area near the break, and kept under 1000deg F, I doubt it will distort enough to be a problem, however you may need to scrape the bore to get it to go back on the overarm. Just do not remove metal from the side of the bore opposite the split, and you will not change the critical center-distance.

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Rusnok repair/ material specs for welding

ddayan

Plastic

Limy Sami

Diamond

mjk

Titanium

gbent

Diamond

Rob F.

Diamond

eKretz

Diamond; Mod Squad

ddayan

Plastic

Limy Sami

Diamond

magneticanomaly

Titanium

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