# Has anyone here machined a new backgear for their Southbend?



## JBuckley13f (Dec 12, 2017)

Hey guys, I've got a southbend 9in model C workshop lathe. My backgear is missing two teeth. I've been trying to decide how to go about fixing it. I know it can be brazed, but I was just wondering if anyone has just made a whole new backgear for their lathe.

Thanks Jim


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## benmychree (Dec 12, 2017)

Which gear is broken?  If it is the bull gear, I'd look for a used part, if the cone pulley gear or the smaller of the two quill gears, I'd make new ones and fit them in place of the original; I recently replaced the cone pulley gear on a 9" Monarch lathe by machining the old gear off and making a new gear to press on and keyed it in place with pins running parallel with the axis, in effect a round key, or keys.
I do not have a lot a faith in brazing up broken teeth, too much chance of one coming loose and jamming up the gears possibly causing major damage.


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## JBuckley13f (Dec 12, 2017)

Its the small gear on the front. Ya maybe Ill go the route of machining off the old gear and press/pin on a new one.


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## benmychree (Dec 12, 2017)

Since this gear is running against the cast iron bull gear, it could be made of steel, so it's ID could be larger than if made of iron, for consideration of strength.


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## JBuckley13f (Dec 13, 2017)

Thanks for all your input. I'll see what I can come up with and post some updates when I tackle this.


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## Cgantner5150 (Jan 11, 2018)

I had a missing tooth on my small back gear. I drilled and inserted hot rolled rod into the holes and tig welded with stainless filler. Let it cool overnight in a bucket of kitty litter. Then filed to shape. Working like a champ.
Before shaping


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## JBuckley13f (Jan 11, 2018)

How is it working out for ya? I've decided to go the route of machining the old gear off and making a new one. Then press/pin/epoxy it on. I figured I could use the practice, its been a long time since I've made a gear. I've got the old gear machined off and my new piece made just need to cut the teeth into it.


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## Cgantner5150 (Jan 11, 2018)

She’s working like a champ. Was using it to make a large steel cannon for New Years Eve. 
I now have a Bridgeport I restored, but have yet to make gears.
Just refurbed an 8” Yuasa Super-Dex so I see some gears in my future.


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## JBuckley13f (Jan 12, 2018)

Awesome! My father-in-law and his brother keep saying we need to make a cannon. I wish I had a Bridgeport, my mill is tiny a little sieg x-1. It's by no means my first choice for a mill but I bought it about 15 yrs ago and didn't really put much thought into it. It hadn't been touched for a good 10 yrs while I was in the army and at school. I just recently tore it down and started to make it "usable" again.


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## benmychree (Jan 12, 2018)

I just replaced the back gear on the spindle cone pulley on my 9" Monarch lathe from (probably) the 1920s; I machined the old gear off, to a diameter that would allow sufficient wall thickness to lightly press on a new gear; I made the new gear of cast iron because I wanted it to run quietly, and avoid steel for that reason; I cut the teeth on the new gear, pressed it on, then drilled and tapped three holes parallel to the centerline on the interface of the old and new gear diameters, 1/4-20 tpi. and then screwed in pieces of bolts with Loctite and cut them off flush with the gear.  Allen head setscrews could also be used to key the old and new parts together in the same manner.   The same approach could be used for the backshaft gear in the project described above, but the teeth could be cut after the blank has been pressed on and keyed; I could not do that, because the cone pulley flange is larger than the gear diameter.


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