How to weld or repair this critter?

I would braze this.

Being it's under stress you would probably be better off if you drilled both pieces for a set of loose press fit steel pins. V the edges some and weld it after the pins are in. The pins will transfer the stress across the joint while the weld holds the parts together. Same idea as Re-Bar in concrete.

I suspect that the broken bit should attach to the outside radius of the half moon shape on the main casting? There appears to be a broken surface there, but it is so clean that it could be a failed weld or braze? It almost looks like the remains of an unfused root between two bevels? It is a strange fracture? How could it have been caused?

Any weld type repair will require bevelling the small broken bit. If you use an OA torch to rough in the bevel then you will have a good test of the type of cast material you are working with, if it burns then it is cast steel but if it just melts and blows away then it is cast iron.

If it is a good quality cast steel then you can repair with steel weld material but if there is any doubt then brass would be my choice, YMMV.

In any case, I would want to disassemble the large casting and use standard preheat and controlled cooldown combined with peening to remove stresses from shrinkage of the weld or braze material. Use an oxidizing flame to burn off the carbon junk that the grinder disk will have smeared on the surface, then use added flux designed for brazing cast iron and do not rely on coated rods for flux.

Good luck, YMMV

Similar concept to what SteveW suggested. Drill it for a pin on both sides and JB weld the whole deal back together. If you coat the pin and the parts and then slide it together with a slight coating on the face of the casting, you will barely be able to tell the fix has been made and it will be plenty strong enough. The pin will be taking the majority of the bending stress on the joint, and the faces will be mostly in tension to separate at the fusion line.

To drill it, super glue the pieces back together and drill through them both for a loose fit of whatever your pin is.

BTDT, worked great.

JW

I kind of prefer the pin and epoxy method.

Welding will probably fail as the weld is cooling.

Brazing would work fine if you were able to furnace braze the sucker and slowly allow it to cool back down, but torch brazing would be a real bitch to try and have it cool slowly and evenly.

Ok..why braze rather than tig?

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary that Roosevelt would be remembered as a great president, "maybe even alongside Washington and Lincoln," opining that Roosevelt "had every quality that morons esteem in their heroes.""

I was originally thinking about a couple dowel pins..but the length and size prevents me from holding the parts in a drill press or mill.

Any suggestions?

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary that Roosevelt would be remembered as a great president, "maybe even alongside Washington and Lincoln," opining that Roosevelt "had every quality that morons esteem in their heroes.""

I think someone tried adjusting the engagement screw improperly and ran it for a period of time in stress..and it finally snapped. Its a clear, clean sheer.

Ok.

Ok

Ok again..so far you make a great deal of sense. Ive got cast iron flux in the welding cabinet. Ill wait for more suggestions and if there are none..try your method.

Thanks!

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary that Roosevelt would be remembered as a great president, "maybe even alongside Washington and Lincoln," opining that Roosevelt "had every quality that morons esteem in their heroes.""

You've got a right angle head :)

Can't clamp it to the bed of the mill somehow?

JW

How about this?: Design a new part that can be bolted onto the old assembly. -Measure everything carefully. -Mill the casting off to a nice, reproducable mating surface. -Make a new part that you can bolt into place to the new surface. Maybe you can even improve upon the original design to make it stronger.

I know several people who have welded cast iron, including me. Out of this dozen or so folks, I'd only let 2 of them within 10 feet of your project (and neither one of them is me).

One of the two recently told me that he just found a "new" cast iron flux that made cast iron welding a real treat.

Pete Stanaitis

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Gunner Asch wrote:

My personal approach would be to disassemble the thing, insert a couple of small dowels for alignment, bevel the edges, heat both parts to 400C/750F, arc weld using 98% nickel rods, peening the weld for each pass, then cool gently.

The presence of a foundry nearby might encourage me to glue the bits together, plug the holes, spray several coats of high build primer/spray bondo over it to give a shrinkage allowance. Then get the "pattern" cast and re-machine.

The reason I'd use the Ni rods is that I've got them. Anything you've got has an advantage over anything you ain't got.

Regards Mark Rand RTFM

You need pre & post heat for *brazing*? Are you sure?

I don't know, but I want to learn, Bob

On a similar rotary table?

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary that Roosevelt would be remembered as a great president, "maybe even alongside Washington and Lincoln," opining that Roosevelt "had every quality that morons esteem in their heroes.""

Ive got a Gorton Mastermill...bigger head than the Bridgeport..the head wont fit.

Gonna be hard. I can do it though.

Gunner

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary that Roosevelt would be remembered as a great president, "maybe even alongside Washington and Lincoln," opining that Roosevelt "had every quality that morons esteem in their heroes.""

Ive got Ni rods as well as Ni tig material, along with silicon bronze, phosphor bronze etc etc.

Gunner

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary that Roosevelt would be remembered as a great president, "maybe even alongside Washington and Lincoln," opining that Roosevelt "had every quality that morons esteem in their heroes.""

My first thought is to drill the center or mill two or three slots around the perimeter on both halves, and put a dowel pin or a few HRS keys between the pieces to hold alignment, then use standard cast iron welding methods - preheat it in an oven or forge and weld it up with Nickel Rod.

Disclaimer: Don't put too much weight on my observations, I've never done anything of the sort. (Never tried stick welding, or worked on busted CI.) I'm just looking at it as a practical excercise.

My Reasoning: You could mill a flat there and make a whole new arm out of steel stock with that setscrew on the end - but you have also totally trashed the piece. And that fork on the end of the busted off chunk looks like it engages that sear for alignment and anti-rotation, and that might be a bear to recreate.

You always need to work on the problem with "the most important tool on your truck" before touching this with any hand or machine tools. It's about 4 pounds, wet, wrinkly, grey and squishy soft... ;-)

Start by setting the bone and trying it again before you amputate the whole limb and fit for a prosthesis.

If you try a simple weld job (or key/dowel and weld) and the weld doesn't hold, you haven't screwed it up too bad and can get more invasive when you develop and try a Plan B.

If you get invasive right off the bat, lop off the whole thing and make a new arm, and that doesn't work, then you are well and truly screwed.

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I've had good luck and no ... uh, very few failures using "railroad rod" and Ferro-flux with oxyacetylene. I think railroad rod was basically just cast iron rod but I can't attest to the metallurgy. I don't know how it got its name. This was a while ago. The cast iron never quite puddles with this technique. It just gets sort of mushy and you then mush in some filler rod. If the cast iron isn't white cast iron, it works great. If it's white cast iron then welding is impossible but I strongly doubt that anything from Troike would be white cast iron.

Unfortunately, the current generation in the welding stores have no idea what I'm talking about and certainly have none of either the rod or flux in stock.

So, today I'd probably braze or braze-weld it with nickle-bronze and O/A. I have TIG but I prefer O/A with cast iron. If done well the strength of such a joint can exceed that of the parent metal.

As for preheat and postheat, it can't hurt. For postheat (slow cooling) I'd just have a bag or bucket of dry vermiculite or pearlite handy (garden store) to cover it while it cools.

I've read about peening while the weldment cools but I've never done it. That might be more for arc welding. I don't think arc (including TIG) welding is the best approach with cast iron. Its advantage is speed, and temperature gradients are exactly what cause cast iron weldments to crack, not always at the weld site.

Seems like the consensus is becoming OA brazing. Im strongly leaning that way.

Thanks Don

Gunner

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary that Roosevelt would be remembered as a great president, "maybe even alongside Washington and Lincoln," opining that Roosevelt "had every quality that morons esteem in their heroes.""