13" Manual Change Gears

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HondaDave

Plastic

Joined

Aug 20, 2018

• Aug 20, 2018

• #1

Good evening. I recently inherited my father's 1943 13" SB lathe. It was in his shop for about 40 years and I'm now looking forward to getting it cleaned up and having it in my shop. I've found that the 80t idler on the gear change set has a broken tooth. The gears are 16dp and 14.5pa. Martin Sprocket stocks a 80t spur gear I could bore and bush, but they are only 1/2" on the face while the SB is 5/8. Any thoughts on whether that would be a problem?

Any one know of an 80t gear looking for a home or have any other suggestions?

Thanks!

 

J

johansen

Stainless

Joined

Aug 16, 2014

Location

silverdale wa

• Aug 20, 2018

• #2

Iirc 5/8" wide 16 dp is good to 200 pounds load on the tooth before the cast iron will fail due to fatigue stress, on the order of 400 to 600 pounds before it breaks off.

That's far in excess of the forces needed for threading. So no problem with a half inch gear..

If you dont have a drill press you can chuck up a #21 drill bit in your lathe and clamp the gear to your tool post to drill the broken tooth for 3 or 4 #10 screws, locktite them in place and file them to get an appropriate tooth profile.

 

H

HondaDave

Plastic

Joined

Aug 20, 2018

• Aug 21, 2018

• #3

Thanks! I hadn't considered repairing the gear. I have a Bridgeport, would it be appropriate to cut a slot where the tooth (teeth, adjacent tooth is also damaged) Is and braze or silver solder in a blank for a tooth?

 

J

johansen

Stainless

Joined

Aug 16, 2014

Location

silverdale wa

• Aug 21, 2018

• #4

Yeah people do that all the time. 80T is pretty close to a rack, you can just cut straight sided teeth, then file them a bit.

 

I

iwananew10K

Diamond

Joined

Sep 12, 2010

Location

moscow,ohio

• Aug 21, 2018

• #5

my memory might be screwy, but *seems* like '43 would certainly be the older style gearbox...AKA "single tumbler" gearbox.....I don't think that uses a 80T idler???

 

H

HondaDave

Plastic

Joined

Aug 20, 2018

• Aug 22, 2018

• #6

Unfortunately it is a manual change, no gearbox. I am on the look-out for a gearbox and a lead screw so I can upgrade though

 

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k3vyl

Stainless

Joined

Feb 13, 2008

Location

newark DE USA

• Aug 22, 2018

• #7

That is a very desirable lathe for a personal shop. The threads that can be made with that machine are numerous if you use compounding of the gears. I looked for one for a few years and ended up with a single lever machine of about the same vintage.Hang on to that machine it will do well by you.

 

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HondaDave

Plastic

Joined

Aug 20, 2018

• Sep 3, 2018

• #8

Just a quick update. I was inspired with the idea of fixing my damaged gear. After looking at it closer it had a half a dozen teeth damaged besides the one broken off. A YouTube video showed a repair process that ground off the damaged teeth, filled the area with brass and then recut the teeth. I don't have a dividing head so I made a 3/8 thick plate with an arbor on it to mount in the vise on my mill, cut a tool for a boaring head that closely approximated the tooth profile, and cut the new teeth. I'm sure its not perfect but it does run quiet plus, I saved $100 that I can put towards a dividing head and a set of gear cutters.

 

I

iwananew10K

Diamond

Joined

Sep 12, 2010

Location

moscow,ohio

• Sep 3, 2018

• #9

Got a pic of the lathe?
Never saw a change gear 13 of that vintage, thus the interest.

 

H

HondaDave

Plastic

Joined

Aug 20, 2018

• Sep 4, 2018

• #10

This is it. Slowly but surely getting it cleaned up.