gear rebuild

[keithh999]

i have a 1939 SB lathe with one broken/missing tooth in the back gear...what would be the best method of rebuilding this tooth?? I have info on brazing or tig welding or mig welding a new tooth and shaping to fit... anyone have their personal preference and method?? am leaning toward mig welding with solid wire and shaping from that but i would like other opinions. thanks

[mike-hr]

I have a 1924 SB that has a missing tooth on the forward/backward carriage feed lever. My lathe may be older style than yours, it has a whole mess of different gears in a separate box and I change them around manually according to the chart on the cover. Anyway, I was getting something done at the local waterjet shop, and mentioned this broken gear to him. He said he has software to waterjet cut straight gears, given all the measurements.. Might be worth seeking your local waterjet shop out. I'm sold on his work, the tolerances the waterjet keeps are pretty amazing.

[IronWolf]

this is not my favorite way to fix a gear tooth but it works ! take's time !
you need to hand file to from or use air tools to get you close then hand file
with Tig you have more control on what youre doing this job can't be done half
way you need to ck gear mesh over and OVER ! DO IT RIGHT you DON"T want
to DO it over !!! take youre time
with MIG you have less control over heat & build up of metal

KEEP IT CLEAN LOL

[R Funk]

Are you certain it is steel?

Many lathe gears were cast iron in which case it must be brazed. TIG would just destroy the gear.

[Phil Patrick]

I have repaired alot of gears on old machines that needed dental work. I dont know how big the gear or the tooth is, but, on bigger teeth, I have drilled and popped steel pins into the broken area, then filled up with brazing material.
You have to take your time, both building up then the final fit of the tooth. A trick you can use is once you are pretty much done, cover the new tooth in dykem or machinist blue, install it in the lathe and SLOWLY BY HAND, run it over a bunch of times. Try to "feel" for binding as the new tooth meshes. Take the gear back out and inspect the dyed area. If you have a big high spot somewhere on it, the dykem will wear of quicker there. Then adjust as you see fit.

Good Luck

Phil

[flat creek]

I have repaired several gears on old lathes by grinding the broken area flat . Then I drill and ream ,then install dowell pins of proper size to match the tooth profile. Then use a die grinder to cut profile. Hopes this helps?

[keithh999]

heres the new backgear gear....just have to assemble the unit so i can fine tune the mesh but its purty durned close now