[How-To] Back gear repair

[Brento]

I do have some silver solder that has the flux coating. But i only have a stick and a half. So i think 3 feet of it.

 

[Manual Mac]

I did not do this repair.
I have had the lathe 40 or so years. Fix was done way before I got it.
i suspect it was done by a machine shop teacher in the 40s to 60s.
probably the two gears were broken off by a student in the school where it lived for many years.
My guess is the broken gears were ground flat at the base, then carefully measured, drilled & tapped for a row of (5) 6-32 screws, then carefully ground to the same profile as the original teeth.
this is not a fast fix but done carefully will work just fine, at least mine has, I’ve done much thread cutting using the back gears.
Good luck with any fix you choose.

 

[deakin]

Do the e bay fix, welding on cast iron will doubtless result in an hard un machinable weld.

that is correct. years past i used to o/a weld exhaust surfaces on cast iron cyl heads. the auto machine people had issues resurfacing that area
(i have since got a machine that surfaces them with no issues but will not cut shapes)

 

[Manual Mac]

this is the 3rd time I’ve recently explained how my back gear was fixed,
do a search on back gears.
personally I would try to fix it like mine was fixed.
What have you got to lose, it is already broken.
i just checked my parts list prices from 6-15-57, back gear Pt.# A536ink2 was 11.75 then.
in 2022 dollars that is $120. A bargain if you could even find a used one.
I’m with bennychree, the eBay fix would be a good fix.
maybe glue it on with locktite, a press fit will probably crack the tiny gear between the teeth.
standard disclaimer, I’m not an engineer, just a retired welder/machinist.

 

[Brento]

I ordered the gear fix on ebay. I will either use the loctite or i will freeze the shaft over night and then heat up the gear and set it in place

 

[ericc]

I do have some silver solder that has the flux coating. But i only have a stick and a half. So i think 3 feet of it.

This is a lot. An inch is a lot. If you are careful, you should be able to do the job with about 1/4" or less, especially if you flatten it a tiny bit. You just want it in the gap. A fillet is not necessary. I just surfed flux coated 56% sticks. Grainger had them for $1582 for a pound. This is a lifetime supply, but it is kind of pricey. The guy cleaning out the lab gave out pieces 1 ft long for free. People were scared of the cadmium, so he gave me a second piece. I've used about 2" in the past 15 years.

 

[DavidR8]

I ordered the gear fix on ebay. I will either use the loctite or i will freeze the shaft over night and then heat up the gear and set it in place

Can you post a link to the eBay kit?

 

[Jim F]

Can you post a link to the eBay kit?

It is in my thread in the SB section.

 

[Brento]

This is a lot. An inch is a lot. If you are careful, you should be able to do the job with about 1/4" or less, especially if you flatten it a tiny bit. You just want it in the gap. A fillet is not necessary. I just surfed flux coated 56% sticks. Grainger had them for $1582 for a pound. This is a lifetime supply, but it is kind of pricey. The guy cleaning out the lab gave out pieces 1 ft long for free. People were scared of the cadmium, so he gave me a second piece. I've used about 2" in the past 15 years.

This is the stuff i have. It is about 6 years old.