I want to learn how to thread so I thought I'd head out to the garage and practice. I have metric and imperial gears for my lathe. The imperial are installed. I thought it was as easy as matching the pitch to the numbers on my lathe. I.E. 26TPI you set to 1 & II on the gear knobs. I noticed all these other letter and number combos that I do not understand. I'm continuing to search but in the meantime thought I'd post here. My assumption is that they are gear positions and teeth numbers. My motor also has a two position drive pulley. Here are the pics. Thanks for any help.