My machinist buddy recently broke a couple teeth off the back gear in his smaller lathe. It is cast iron. He is not a welder, but asked me if I had ever welded cast iron. The only time was on a Ford steering box, and I used a MIG, with much success. Same wire as we used to weld steel sheetmetal. I think I probably lucked out on the Ford box because Henry used a lot of steel in his iron, and that might have made it easier to weld. Now this gear doesn't look like any kind of nodular iron. It has a really rough and grainy surface where the teeth were. It's a 1980's Enco (China made) lathe. Can anybody give any recommendations on doin the welding with a MIG? I'd probably clean the hell out of it to remove oils, heat the whole gear with a torch flame, weld the teeth in a few passes, then let it cool very slowly with maybe a soft flame waved over it now and then. On the steering box I peened the weld right after the pass, but I don't think we want to go pounding on these gear teeth and risk nicking the good ones. He will hand grind the teeth back to shape using blueing to verify the contact pattern. Or, is using a TIG even possible? He said they had used some special sticks when welding a broken keyway on a crank that let them machine easily. Maybe scraping the coating off those rods and trying to TIG with them would work? Anyway, I'd love to hear some opinions from guys who have done this before. Or even guys who might have old Enco parts lathes sitting in the back of the shop.
The last time I had cast iron welded, if you were to call it that, it was done with brass. After I had gotten the part back I realized that I could have done it myself as it had been done with a torch.
I like to use a TIG machine on cast iron. I would go with a 2% Thorium tungsten. Shielding gas of 75% Argon and 25% CO2. I have had good luck with Blue Demon ERNI55 welding wire. Pre heat it to about 600 degrees and when you are done with your weld let it cool very slowly. Welding teeth on a gear is a real challenge.
When you said the year and country of origin,,,,,I felt bad for thr guy . If it looks like cheap iron,,,it probably is . You are right,,,,,,Ford used some high grade iron in a lot of his pieces . A lot of the old manufacturers used high nickel iron,,,,and other ingredients too . Just think about the old flathead cranks,,,,,cast steel yes,,,,, but,,,,,extremely strong . I wish your friend luck with his lathe gear,,,,,,but I can’t imagine how it broke,,,,unless it was just getting ready to fail anyway,,,,you know,,,,weak iron ? Like has been said,,,,,,,probably have good luck with brazing it back up,,,,and smoothing it back in ? Tommy
On my southbend lathe i brazed where the old teeth were then filed the teeth into the brass been like that for 26 years jimmie
DITTO I repaired the back gear on my lathe by brazing up the broken tooth with an acetylene torch and hand filing the tooth profile and it has lasted for decades. Full disclosure: When operating in back gear I now take smaller cuts out of fear of breaking the back gear again, but nope. I also have TIG and MIG capabilities. If I were to try TIG I'd use nickel rod, preheat and cool slowly.
Brazing would be the first choice but if you do want to try welding it use nickel rod with a stick welder, preheat and cool slowly. I have also seen gears repaired by finding another gear with similar sized teeth and cutting out a section of maybe 4 or 5 teeth, then welding in that whole piece instead of trying to do an individual tooth.
Most of those lathes came out of the same factories, if he can cross it to a Grizzly model he may be able to get parts. I've got a HF lathe and was able to use parts from them on mine.... It might also be worth checking with McMaster-Carr as they sell a pretty big selection of gears.
The others have said what I was going to, i.e. use braze to build up the teeth. I was also going to say that the load on the back gears is very light, as they are only used to turn the lead screw, not the spindle. But then I'd like to know what caused the teeth to break. Was it a heavy cut in the lathe, or was the gear dropped or suffered other non-operational damage? Even so, braze is probably as strong as crappy cast iron. Crazy Steve has good advice for finding a replacement. Even a gear "blank" that had the right tooth count and diameter, etc. if available could be finish machined to suit.
Ni-cad rod. Good info here. https://www.lincolnelectric.com/en-...-detail.aspx?utm_referrer=direct/not+provided
The best method for you will be the one you have had the most success with. If you are good with brass or bronze, you don't want to be fooling with TIG or MIG. If you use bronze, and it is plenty strong for that job, try Eutectic 16FC rod. It is flux coated and flows very easily. It is very strong, we use it on flathead valve stems to lengthen them. We TIG weld most cast iron, like making a model A block into 4 intake ports or moving flathead V8 ports all to the top deck. We use ER70 1/16th rod. Preheat to 300, weld 1/2 inch and peen either by hand or with air chisel turned down, keep the weld area warm till done. Put blanket over the work to cool.. One thing though, if you have never done this, YOU NEED TO PRACTICE BEFORE DOING THE GEAR ITSELF. If you can TIG a row of dimes on steel, you will pick this up quick.
Saw this a couple days back if you have the time he welds cast iron with a torch and cast iron ROD. Don't know where he got it but it works. https://bangshift.com/bangshiftxl/r...-from-the-1870s-is-an-amazing-amount-of-work/
I am familiar with TIG on mild and forged steel, and am not really too bad at it. Not always a row of dimes, but I understand the principle and can make a strong weld. Just never done it on anything cast. I have never brazed though, so that would be all new to me. I may see if I can get some of that rod that Pete used and try some practice TIG on iron. I'm sure I can find an old engine block to practice on. Please keep the advice coming.
The sheilding gas I have is 100% argon. Woodiewagon recommends a mixed gas. Will my argon work OK, or that dependent on the rod you use? Pretty sure I have some 2% thoriated tungstens.
Assuming he still has the teeth and they fit into place nicely I would look at silver soldering using a torch. Use Harris Safety-Silv 56 or similar. It is essentially a brazing process, bit is very high strength. Back in the days of machinist having to make their own cutters it was used to attach all sorts of stuff to other stuff. You will want to bake the oils out if the casting and use a stainless brush to hopefully knock out and surface carbon. Heat, flux, and clean until you think you have it. Clamp lightly together and hopefully it will flow into the joint. If it won't flow it you may need to relieve some areas for it to flow into, but leave enough casting to hold it in its original position. If I remember correctly it likes maybe a few thousands worth of a gap to flow into.
My small lathe had a missing tooth on the back gear, I took it to a machinist who made a new tooth, drilled and pinned it in place then looks like added braze to it, I assume with a torch. That was 25 years ago. I don’t use the back gear very much so unsure how it would hold up to daily use.
He doesn't have the teeth anymore. He broke these two off by locking the back gear into the normal drive gears to unthread the chuck. Says he's done it a million times before, but it had been on a few years since the last time he removed it. We were discussing a different way to lock the main shaft for removing the chuck next time, after this is all fixed. He said basically he only uses the back gear for threading operations. So if the new teeth were slightly less than original strength they would probably still be ok.
asian iron is gonna be oil soaked and generally dirty beyond belief.... baking some of that out before a fix is attempted should help regardless of your approach to fixing it. you ain't got the original teeth and thats ok , it's a pain in the ass to fix that way. Building up with brass and filing to fit is time consuming and tedious but it'll work. As far as what braze to use in terms of compatibility....good luck ,cause it's a crapshoot, but it's the world we live in.
Preheat and post heat when welding cast iron are extremely important to whether it works or not. And sometimes even when you do everything right it can still fail. But considering it's broken teeth, the worst result is it's still broken when you're done. Be sure to preheat to 500-600 degrees, and have a welding blanket handy to wrap it in as quickly as possible when you're done to avoid it cooling too quickly. If you have to stop during the welding, have a torch handy to direct heat on it to maintain the temperature while you've stopped. I had a BBC years ago that when magnafluxed showed a tiny crack less than 1/2" long on the bottom of one cylinder bore. Machine shop sent it to a weld shop specializing in welding cast, and they took all the proper precautions. Since this was a year correct 402 BBC I wanted to keep it numbers matching. But once it was successfully welded they wrapped it up, and returned it to the oven to slowly let it cool. As it was in the oven cooling the shop said they heard a loud bang, so they opened the oven to check it. The weld was fine, but the block had cracked across the lifter galley making it into two V4's!! Ended up having to find another 402 BBC bare block, which had already been bored .030", and have it bored another .030" to .060" and send my pistons back to exchange for the larger size....and no numbers matching, but at least the same year.
Might want to consider Tig "brazing". That way you have better control of the heat and don't have to melt the parent metal........though you probably need to file it a little so there is a place for the braze to attach and hold. Then just file the excess braze off.
crow cast welding in Hudson Wisconsin will put it in an oven, and spray weld it all back up to size, and you or he will cut the teeth back in it. probably not cheap, but done forever. google it up, very interesting place
Another thought that may work without welding, look for a gear the same size. Tooth count as well. Machine it out and machine off the teeth of the gear and make a press fit. Of course try to repair what he has first, just tossing out another option.
This is an article in Hemmings Motor News https://www.hemmings.com/stories/20...aily&utm_medium=email&utm_campaign=2021-02-24
I would stick weld it. There is a lot of fool proof cast rod these days. Or you can always go to the old standby Ni-Rod (nickel). Preheat to about *400 degrees and weld little short bits at a time. Then peen the hell out of it. That always has worked for me. *@400 degrees spit or a little water will roll into a bead and skitter off.
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