So, I've been posting about this on my FB page for a while. Last month we had an incident using a cut-off tool on the lathe getting the holder into the chuck, and well, it took about 5 teeth off in one spot, and 1 more in another. Or maybe that one had been missing, who knows.
In any case, the lathe came to an instant stop and made a hell of a noise. So, dad got the cover pulled off and thats what we found. A long with a small clink, clink, clink, clink which was the little pieces of gear teeth that had been stuck in the grease of the cover falling out onto the shop floor when we took it off and stood it up.
I did a lot of research online about the gear. Southbend Lathe Co. has changed hands in the years past and doesn't stock or have parts like they use to. I found the # for one parts place and as it turns out apparently all the records for any lathes pre 1939 were lost or destroyed. There are no original blue prints left to even re-make this stuff. I scoured ebay, couldn't find anything that was the same size swing as ours. I found plenty of smaller ones but nothing as big as this. Dad was honestly to the point where he thought we were going to have to scrap the thing. He mentioned it a few times even. Having a gear shop in Jacksonville tell us $150 a tooth was really what brought that thought on considering there were no replacements. Honestly the machine is old as sin, completely worn out and probably about .020 out of round tolerance. Its not precision anymore, but it works and does bulk work rough cuts stuff fine still. Plus, its a cool ass piece of machinery. Most everything in the shop is early equipment and I wasn't ready to give up on it. I've always heard "You can't weld cast iron." Well, me being me of course had to call bull-on this and give it a try. Besides it was basically a paper-weight at the moment anyways. I've got the Lincoln welding Handbook, which is sort of the bible for welding information. I read through it and it recommended 99% nickle rod for cast-iron if there was going to be any type of machining available. Everywhere I looked online said something different. Some places said stainless, some said just regular 7018 stick welding rod, all kinds of ridiculous things.
At the end of the day I figured the Lincoln Welding folks probably knew what they were talking about so I went with their recommendation of 99% Nickle rod with a plethora of pre and post heating of the weld piece. Cast iron is very brittle. The heat spreads out the material and makes it expand. As your welding on it you are naturally drawing the metal together, tighter. So heating it helps counter act this. If you dont preheat, it just pulls itself together and it cracks. Badly.
What I had for rod was some 3/32 99% nickle stick welding rods from the local welding supply house. They are about $40 a pound which sucks. I inteded to tig weld this for better heat and puddle control. I knocked the flux off the rods and wire wheeled the little bits off till they were clean. I don't have the picture of it here for some reason, I never took one before I started welding. I degreased, and degreased, and degreased. I then actually hand filed the old broken teeth remnants off (I'm not a fan at all of grinders for work like this or working on thin wall tubing or anything where any level of precision is required). I then pre-heated it to help bake any remaining oil residue out. I didn't make it cherry red or anything, just heated it up good and kept it even to where it was smoking some. I struck up an arc and used up a few and I got pretty much what you see above. Initially I was very worried because the base material was soooooooo porous. When I got a puddle started and you actually seen the base metal under it, it looked like a sponge it was so rough and full of pin holes. It was scary as hell. I figured this filler metal I had was just going to pull right out of the base in one big solid chunk. I finished welding it and by the time I had filled the area where the 6teeth were missing, the top portion of the gear was a dull red. I grabbed the torch and gave it a good post heat to evenly distribute it at the bottom and other places where it wasnt as hot and then left it about 2 hours to cool fully, naturally. No cracks.
After being welded up, It went on the other lathe and very carefully with very light cuts got the outside diameter turned down to approx the same as the remaining good teeth so there wasn't an excess sticking out. It was nerve racking when those first few cuts were being made because I was at this point, from the condition of the base metal I seen when I was welding it, expecting the whole piece to just snag and come flying out at one time. But it didn't. It kept turning off little bits and shavings until it was down to what you see above.
Then we got really lucky. Dad made a contact with a gear shop in Jasper, FL the next town North of here. They did some stuff for him years ago when the transmission on a John Deere combination load backhoe went out. They had moved from their shop here in Live Oak though and we had a hell of a time tracking them down. I took the gear by welded and turned back round with the lathe and let them look at it. Dad and I had figured from the gear pitch gauage we had in the shop that it was a #10 gear pitch, and it was. They had the gear hob to cut the teeth and everything right there. Turns out its a very standard gear pitch used on a lot of stuff. Told me to weld up the other side and bring him $100 with about a weeks worth of time and the would do it up. I got it back today, and I'm really happy. I'd call it perfect, but unfortunately one of the things I encountered welding this trash is that although with some effort the filler metal will stick to it, the base metal "erodes" around it. So no matter how much you build up around it, wherever you stop at, its got little undercut looking edges. And that made the places where I stopped at look a bit ratty, but it is what it is. I got $130 in it and about 45min welding and preheating time, with about another 45min turning down the weld on the other lathe to prep it for the gear hob to cut the new teeth. Jax shop wanted $150 per teeth, 6 teeth missing =$900.
So while I'm building 500R conversions, swing-arms, and whatever else in teh shop, if someone needs some cast iron worked on, let me know :P That $900 repair quote pissed me off just enough to do it myself!
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Originally Posted by 300rman
