Have you ever seen a 1-7/16 x 8 thread??

Terrywerm

Terrywerm

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Someone I know told me of a lathe with a threaded spindle with a 1-7/16 x 8 thread. I don't know what brand the lathe is, and have not yet seen it for myself. I suspect that it is actually 1-1/2 x 8 but someone measured the OD incorrectly.

Has anyone else ever seen a 1-7/16 x 8 thread??
 
Very strange. Rare as hen's teeth and I'm amazed bill tracked down a production tap.
 
Okay, we know the thread exists, which really is no great surprise, so maybe I should rephrase the question. Has anyone else ever seen or know of a lathe manufactured with a 1-7/16 x 8 thread on the spindle?
 
Don't rule out metric with a TPI pitch. One of my Jet lathes is 1 1/2" x8tpi and the other is 60mm x 8TPI. Apparently there is not a course enough metric standard thread for a spindle so they were doing them up weird. Just thought I'd mention it. maybe 36mmx8tpi.

Really I don't even know if that is a size that was used as I have never heard of a lathe using it (or 1 7/16" x8) but then again I never heard of 60mmx8tpi until I owned a lathe using it.

Steve
 
Threads can be virtually anything you want, so it's certainly not impossible for it to be a 1 7/16" - 8. Until you measure the PD though, you can't be certain. The major diameter can be worn down, or simply cut undersized by accident. In order to precisely identify the thread, all the major elements must be accurately measured. That means the major and minor diameters, the lead (or pitch), the flank angles, root radius, crest radius (or flat in either case). It could be Metric, for all we know at this point.

Is this lathe accessible for measurements, or is this an academic question?
 
Thanks for the replies, fellas.

Tony, the question is purely academic, but I thought it a good idea to bring it up in case anyone else has ever seen this.

I was told of a lathe that supposedly has that size thread on the spindle, and was asked if I thought that a backplate for a chuck with a 1-1/2 x 8 would work on it, as the owner is interested in purchasing a new chuck for it. I do not know the owner, but Russ (a friend of mine) does. My thought was that if the actual diameter is 1-7/16 a backplate for 1-1/2 x 8 might work, depending on the register diameter. I told Russ to tell his friend to measure the register step and see what diameter it is, then decide from there. He may have to purchase a blank backplate, then bore and thread it to fit.
 
Terry, I'd be very cautious about using a standard 1 1/2" back plate until I could be sure about the thread. If it is indeed a 1 7/16 thread, you would lose a significant amount of surface contact on the thread flanks, although you are correct in saying that a properly fitted register would center things up. It would be, IMO, too weak to use.

If the owner has the capability, I'd want to know at least an over wire measurement. We could get a better feel, at least, for the likely candidates.
 
When I first read the post I thought you said 1 7/8"-8. Old Southbends 10R with a 1" spindle had that size. It a little hard to find cause the heavy 10L is more common with the bigger sbore kellybore kelly
 
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