since ive been welding i havent really tried changing the cup sizes. always using a #6 or 7 with a 3/32 tungsten. however i never eallly learned the purpose of changing the cup size>? anyone care to chime in and let me know when changing to a smaller or bigger size is needed >? as well as purpose? and does this go same for gas lense usage>

 

i dont know what sizes are needed but you could always get a tig calculator they tell you ,

 

I don't know any specifics but when I'm doing aluminum I switch my cup to a #5 and it works a ton better for me. Sorry i can't be a little more technical this might help.

http://www.ckworldwide.com/tech-6.pdf