Hi- I just got a CB3200 last week. I'm not trying to use it for leather - it's for nylon webbing for parachute harnesses. Using #346 nylon thread (5-cord) with a #26 or #27 needle. Although it seemed fine when I tried it out at the dealer (with some other kind of thread in the bobbin), it doesn't seem to want to get the thread lock up off the bottom. I maxed out the upper tension. I am going to try bringing it back to the dealer to see if he can figure it out.