Hi Guys, can anyone help with info on timing pulley dimensions? I need to make some 3mm pitch pulleys and the maths is driving me nuts! If you multiply the number of teeth of your pulley by 3 (pitch) you get the circumference and from there you can calculate the diameter. So far so good. When you cut the pulley the pitch is too coarse. Not good! I have some commercially made pulleys and measured them and the diameter of a 13 tooth comes out at 11.6 mm and the calculated diam is about .8 mm bigger. This is unfortunately not a constant and will increase with larger pulleys.(i think!)
Any suggestions
Les

Hi Overloaded, Many thanks for your info, it has sorted out my frustrations no end.
best regards
Les