SB 9" left-hand leadscrew?

Its possible we have one. We have a 9" South Bend w/ changegears in the back shop at Tuckahoe. It came in as a project lathe and is nearly together. One of our members contributed a leadscrew he bought from Plaza Machinery, which was reputed to be for a SB 9.

The pitch and various diameters are good, though the left-hand leadscrew support needed to be counterbored to fit. We got the toolpost mounted today and set up the gearing for 8tpi but experienced threading troubles. As we dug into the leadscrew and halfnuts, Dick figured the leadscrew was left-handed. We checked it against a couple bolts, and the leadscrew of the Flather next to the SB. It is indeed left-hand, and is definitely a leadscrew and it definitely fits the SB (modulo the counterboring above).

Which leaves us wondering, "What the Heck?" It also means we have to find another leadscrew, hopefully one w/ right hand threads.

So Dick and I were wondering if SB did in fact supply left-hand screws in some cases & we got lucky, or is it more likely this is something from some another sort of machine entirely but happens to be close enough to a SB version to be mistaken for it.

Thanks,

Greg

Greg,

Here's your answer:
The SBL Workshop - 9" Workshop information
Take a look at the first section, regarding the "405 with bench drive". I also took a cursory look at several catalogs on Steve's site, same era, but didn't find mention of the left handed lead screw.

Paul

left hand lead screw on a workshop lathe

Hi

The very first workshop lathe was built in 1934 and part of 35. These very early 9 inch lathes had a left hand lead screw thread. They also did not have a shifter to reveres the lead screw rather you had to add a fourth gear to the banjo. These were known as the catalog 05 lathes most of them were the 405 version with the rear horizontal drive. With the introduction of the catalog number 415 in late 1935 SB switched to a normal right hand lead screw and added the shifter to the head stock. The right and left hand lead screws will interchange as will the half nuts so its possible to have a miss matched set.

Turk

leadscrew

I can turn your halfnuts into a normal right hand thread if you like. Reworking the leadscrew is also possible. Give me a call or text at 913 636 6107. Thanks Mike

@Dennis- many thanks. This is definitely a Frankenlathe, so a mismatch is probably the culprit. Not sure if we want to retrofit a right-hand leadscrew (would involve cutting and turning down for the shorter bed), or try to find some left-hand halfnuts- the extant halfnuts are almost entirely worn out anyhow...

So does anyone have a set of left hand half-nuts they'd be inclined to sell?

Greg

Greg Menke said:

@Dennis- many thanks. This is definitely a Frankenlathe, so a mismatch is probably the culprit. Not sure if we want to retrofit a right-hand leadscrew (would involve cutting and turning down for the shorter bed), or try to find some left-hand halfnuts- the extant halfnuts are almost entirely worn out anyhow...

So does anyone have a set of left hand half-nuts they'd be inclined to sell?

Greg

Click to expand...

It would probably be cheaper to get a RH leadscrew. I have one set of LH half-nuts left...$250
Ted