01-08-2023, 11:21 AM
Is your leadscrew metric or imperial? 
I found this on the lathes.co.uk website. Not sure if it's applicable to your version of the lathe.
"Screwcutting was taken care of by a 4 t.p.i. 7/8" in diameter leadscrew driven from an enclosed, splash-lubricated gearbox operated by two dials and capable of generating 30 pitches from 10 to 76 t.p.i. and 30 sliding feeds from 0.001" to 0.0076" per revolution of the spindle. While the sales literature claimed that additional changewheels of 30t, 60t, 60t, 110t and 120t were provided with each machine to extend the threading range from 2.5 to 75 t.p.i. (and the feeds from 0.001" to 0.030"), an examination of machines in use appear to indicate that the original gear train (for a gearbox-equipped lathe) used a 30t drive gear, 110t idle gear and a 120t gear on the gearbox input shaft. Stored outboard of the idler gear and gearbox input shaft were gears of 45t and 50t - but with no sign of the 60t gear. At extra cost an additional nine (unspecified) changewheels were available to generate metric pitches from 0.20 to 8.0 mm pitch (these likely to have included a 127t or 63t.)"
Ed
I found this on the lathes.co.uk website. Not sure if it's applicable to your version of the lathe.
"Screwcutting was taken care of by a 4 t.p.i. 7/8" in diameter leadscrew driven from an enclosed, splash-lubricated gearbox operated by two dials and capable of generating 30 pitches from 10 to 76 t.p.i. and 30 sliding feeds from 0.001" to 0.0076" per revolution of the spindle. While the sales literature claimed that additional changewheels of 30t, 60t, 60t, 110t and 120t were provided with each machine to extend the threading range from 2.5 to 75 t.p.i. (and the feeds from 0.001" to 0.030"), an examination of machines in use appear to indicate that the original gear train (for a gearbox-equipped lathe) used a 30t drive gear, 110t idle gear and a 120t gear on the gearbox input shaft. Stored outboard of the idler gear and gearbox input shaft were gears of 45t and 50t - but with no sign of the 60t gear. At extra cost an additional nine (unspecified) changewheels were available to generate metric pitches from 0.20 to 8.0 mm pitch (these likely to have included a 127t or 63t.)"
Ed