I've repaired more than a few cast iron things for people over the years and its just never been a "mistake" to go with Bronze Brazing. Any kind of arc welding on the other hand well, let's just say I mostly ended up wishing I'd of never tried it.

 

Hi farmersamm. The suggestion to use low fuming bronze sounds like just what I need. I was hoping to weld it, but it's looking too tricky. I have an oxy fuel torch and a tig welder, so this should be good.

 

Hi hobbytime. Yes. I was actually using tightening when I encountered the problem. I think that this weld is just beyond.y skill level.

 

I replaced a missing cast iron tooth on a big music box spring-motor using regular old 70s mig. Ground it back to shape with a thin cutting wheel. It's been working for about 10 years now. Just do dabs and build up and you won't heat the cast iron up much at all.

 

Doug,

Thanks, that is what I was curious of, if it was possible to build up rod on the missing tooth to not overheat it.

I have a similar job to take care of at some point.

I guess it couldn't hurt to pre-heat cast iron first, that was what I was curious to understand?

Alan

 

This is dating me but I have done bull gears on two lathes in the 1970's. I torch brazed making it easy to machine after and the lathes were still running in a school shop when I left. A good brazing alloy will match the strength of grey cast iron and has the bonus of being easily machinable. Dealing with the heat affected zone when machining cast iron repaired with weld is not pleasant.

 

That LFB (low fuming bronze) rod used for "braze welding" (like in that video) does its thing up around 1600 F.

 

You're right, I got my numbers mixed up. Ought to know, been using the daylights out of the stuff lately. http://www.harrisproductsgroup.com/...sgroup.com/en/Products/Alloys/Welding/Copper-Alloy/Low-Fuming-Bronze-15-FC.aspx

Important thing is, that it's below the melting point of steel/iron. And it comes with its own safety valve.....................When the metal is getting too hot, the stuff won't flow, and starts popping. Lets you know that it might be time to go have a cigarette, and cool your heels for a bit.

It's been the go-to on my lathe restoration. I'm able to join materials without fear of burning through thin sections, build up wear surfaces, and join dissimilar metals with ease.

So far, I've had no problems with undue distortion from the heat. It seems way more forgiving than welding. As long as you control cooling, there have been no cracking issues either. I'm becoming a real fan

 

Sammm nailed it

 

https://www.youtube.com/watch?v=bZ7vxFfG3S4

 

Bronze buildup is common, then recutting the profile. Thing about brazing is that it's less shock to the cast iron. Flows out, and bonds, at about 800 degrees. You don't have near the cracking issues you could have by trying to weld it.

Preheat the area around the broken tooth to about 500, then start brazing. When done, wrap the gear in welding blankets to allow it to cool slowly. You can also post heat to cool it down gradually before wrapping it.

Barring all that, you might be able to find a stock gear from Boston gear,, or one on Fleabay, and remachine to fit your application.

PS.......I remove stuck chuck by wedging a bar in the chuck jaws, and unlocking all the gear train, then gently rotating the chuck and bar against a block of wood on the bed. The inertia, and soft thump on the block, will generally spin 'er off.

 

Might be a long shot, but what type lathe, or size gear? I have gears from a 16" south bend cone head.

Steve.

Sent from my SM-J700P using Tapatalk

 

That's what I'd do. The old machine tool community are pretty cool and hobby machining forums have a lot of info. Also check Ebay.

Inconel 600 wire was used (probably not quite the correct filler).

Everything about repairing old gear teeth was known before anyone reading this was born. You might ask Abom or Keith Fenner on Youtube how they do it. There's no point in experimenting on parts you want to save.

I'd also consider Crown Alloys cast iron MIG wire. aametalmaster's posts gave me the idea to turn my machinist bros onto it as they repair a lot of ancient cast iron meat processing equipment. They bought a roll, welded some test pieces then applied "scientific sledge hammer" testing. Now it's their go-to cast iron repair.

 

do you have access to tig? if so try 309 rod, over build the tooth then machine to shape..

 

The key phrase being, "machine to shape". That stuff is HARD. A dremel/rotary-tool could assist if a mill wasn't available. Gears are not easy to cut, those type of involute gears are not straight forward to do on any mill. This is probably the reason the OP is trying to repair one.

For the application the OP mentioned in this thread, it seems the biggest danger will be having the cast iron crack. Even when pre-heating, cast iron is known to crack. Some people will say it's only a matter of time.

Is it possible to use tig with extreme pulsing to keep the heat down and not have to pre-heat, or would it most likely need to be pre-heated? IOW, can you use short bursts of high amps, with long latency in between in order to heat a small area you could build up some rod on, until the tooth was larger than full shape (i.e., to machine/shape tooth).

EDIT: Seems the best way would be to take the cast iron to about 1200-1400 degrees, slowly, before starting to tig, is that right? (or would you go higher?)

I have brazed one tooth in the past and filed it, came out ok, nothing to write home about...but that was before I had access to tig.

Alan