Piero
Member
- Messages
- 1,396
- Location
- Uk
Hi Guys
I am trying to work out the formula for cutting a metric thread on my imperial Colchester Bantam Mk1
I have a manual for my model and it does give a formula
BUT its very unclear as to what and where certen values come from.
I have added two photos from said manual, and if we take the simpluar first Example for cutting a 26 tpi it gives the awnsers as needing a 42t driver and a 39 driven,
I can follow the 7 x 12 as 12 being the value for lever position 1=12 and I follow the 3 x 1 as lever position A=1 and 26 is tpi but how then do they get 14 and 13 and then to make 42 and 39
to make things more complicated, look at metric thread pitches (see second pic)
can anyone spread some light ????
I would ideally like to master the convertion, but for now I am trying to cut a 5mm metric pitch thread on my imperial lathe with screw cutting gearbox
I am trying to work out the formula for cutting a metric thread on my imperial Colchester Bantam Mk1
I have a manual for my model and it does give a formula
BUT its very unclear as to what and where certen values come from.
I have added two photos from said manual, and if we take the simpluar first Example for cutting a 26 tpi it gives the awnsers as needing a 42t driver and a 39 driven,
I can follow the 7 x 12 as 12 being the value for lever position 1=12 and I follow the 3 x 1 as lever position A=1 and 26 is tpi but how then do they get 14 and 13 and then to make 42 and 39
to make things more complicated, look at metric thread pitches (see second pic)
can anyone spread some light ????
I would ideally like to master the convertion, but for now I am trying to cut a 5mm metric pitch thread on my imperial lathe with screw cutting gearbox