Only I could do this...

[n9viw]

Not only do I manage to find the single rarest spindle nose thread in history (SB 10R, 1-7/8"x8), but I also managed to find the OTHER rarest item in history... a back plate in 1-7/8"x8... LEFT-HAND THREAD.

Does anyone have any idea what machine this would even go to?

I wrote back to Jason at Lost Creek to see if I could return this, but I don't know what their return policy on used stuff is. I may have to find an application for it, then market it to that narrow subset while I continue to look for a plate for this goofy lathe.

 

[MyLilMule]

1-7/8x8 (right handed, that is) is a very common spindle nose thread. Usef on many South Bend Lathe models. I would guess hundreds of thousands of them were made. My 1942 13" uses that thread.

 

[n9viw]

Then we're in the same boat. In my web and paper product manual searches, I've been led to believe it is far outshone by more common spindle sizes such as 1-1/2"x8 and the 10L's 2-1/4"x8. Yes, 1-7/8"x8 does exist, however hard to find extant examples may be. But left-hand? I haven't even found an application for that, in lathe or mill.

 

[MyLilMule]

Yeah, the left handed is weird. Especially since you'd have to run the lathe in reverse to keep it from spinning off. I wonder if it was made for a tail stock or something.

As far as 1-7/8 x 8, there are plenty of those to be found. You can even by partially machined back plates in that pitch. I have one I meant to use on a 10" 4-jaw, but never got around to it.

 

[CJ5Dave]

Still rarer is my Sebastian lathe. 2 1/8 x 8 TPI. Not sold in stores.

 

[francist]

Any chance it’s a faceplate and not a backing plate? If so, a larger woodturning lathe that has outboard spindle capacity will have left hand threads there but standard right hand on the inboard side.

 

[n9viw]

Any chance it’s a faceplate and not a backing plate? If so, a larger woodturning lathe that has outboard spindle capacity will have left hand threads there but standard right hand on the inboard side.

No, it's definitely a back plate. 4 countersunk holes for a chuck. 3-13/16" O.D., if I recall correctly.

 

[n9viw]

Yeah, the left handed is weird. Especially since you'd have to run the lathe in reverse to keep it from spinning off. I wonder if it was made for a tail stock or something.

As far as 1-7/8 x 8, there are plenty of those to be found. You can even by partially machined back plates in that pitch. I have one I meant to use on a 10" 4-jaw, but never got around to it.

I'd love to see the ones you've found! So far, I have found exactly one. On ebay, it comes with an R8 collet chuck. $225. The same company used to have one that came with a 3-jaw scroll chuck, but they're out of stock and have been for a while, and no idea when they'll get more. Chinese, but ain't they all anymore.

I think I'll do like the savvy boys do and make one. I don't know how to thread, so I'll weld a McMaster nut to a slab of HRS and carve my own. I have access to a mill at work, I'll gouge out some slots and make a 4-jaw of sorts, that'll at least get me started.

 

[matthewsx]

I had a machine with an orphaned spindle nose but it wasn’t as simple as being threaded with a strange thread.

I eventually found the specs for it and figured out how to adapt a different standard taper. But, that machine (Bolton) had bigger problems and I got rid of it.

If I were in your shoes I’d ask if any of our members would be willing to bore and thread another adapter to match your spindle. Should be fairly straightforward to take a 1 1/2” adapter and make it into what you need. Even have them do a few which you can then finish for whatever chucks you need.

John

 

[n9viw]

I was actually thinking of getting a few of those McMaster nuts. In my mind, once I made a chuck of sorts from one, I would practice threading scrap metal. Once I got the hang of it, I would thread on one of those nuts, turn down the shoulders, and size and thread it to 2-1/4x8, so I could use the 10L plates and chucks.

Yes, I could just swap out to a 10L spindle and headstock. There's one on ebay right now for $450, which I don't have. I couldn't think of any application for which I would need that extra 3/8", so I figured I'd use what I have.