The gear pressure angle is 14 1/2 degrees. All the South Bends had 14 1/2 except the Turnados, and the 12"(from the 70's), and of coarse the imports.
Ted Pflugner
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the standard stud gear for the 13" with a single tumbler gearbox is 18 tooth. Other stud gears can be used to produce threads that are not on the standard index plate
Ted Pflugner
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There were two versions of the single tumbler set up. Early ones had the slide gear and would cut 2 to 112 TPI
Later ones also had the slide gear,but would now cut 4 to 224. Plainly the stud gear was made with half the teeth used before.
If your box data tag says 4 to 224 and you have a 36 tooth stud, it is set up like the early versions - it will cut some threads that are not even on your tag.
When using the feed, the finest feed on the early version was .003 IPR. The early tag made no mention of feeds, just threads. The later version (that is marked 4 - 224) has the related feeds marked on the tag, and the finest feed is .0015 IPR.
We assume you are familiar enough with the lathe to realize that when feeding, you use the apron gearing and feed clutch knob and NOT THE HALF NUTS AND LEAD SCREW If you neglect this important detail, the very finest "feed" available with the 36 tooth stud will be .0089 IPR if you are trying to "feed" with the half nuts.
John Oder
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