Schaublin 102vm gearing for metric threada

[swehollow]

Hi folks. I'm trying to set up my 102vm to cut metric thread 1,25. I don't understand the gear chart since they say F is the lead screw and in several of the metric pitches there is no gear connected to the leadscrew! Then how is the leadscrew supposed to turn.. . I'm missing something, please help.

 

[dnp]

I have the same lathe. The last gear shown in the table goes on the leadscrew. In the case of 1.25, the 90 tooth gear.
This can be verified by the formula A times C divided by B times D is the same ratio as 1.25 divided by 4.
50X45=2250
80X90=7200
2250/7200=.3125
1.25/4=.3125

 

[Charles_nl]

Hi folks. I'm trying to set up my 102vm to cut metric thread 1,25. I don't understand the gear chart since they say F is the lead screw and in several of the metric pitches there is no gear connected to the leadscrew! Then how is the leadscrew supposed to turn.. . I'm missing something, please help.
View attachment 256013

But you are absolutely right and I never noticed this silly text and indeed also the formula. As dnp said the last gear goes on the lead screw. But in the case of only 3 gears used (the pitches from 1.5 - 6 mm) the formula should be a/d (because c is just an idler and its size is immaterial - actually the formula is a/c * c/d)