I'm having problems with my sewing machine. I'm trying to hem up some jeans for my shorty-short daughter, but I can't seem to get the tension right. I'm using a jeans needle and some heavy weight thread. For some reason, I keep getting locks on the underside. My machine manual tells me this is because there isn't enough tension on the spool, but I have the knob turned all the way up on 9 and it's still happening. I even tried adjusting the tension on the bobbin, but that didn't do anything for the problem. I've run the spool thread under the bobbin tension thingy (if you use a machine, you know what I'm talking about) that is next to the slot for the thread, but that only worked temporarily. I'm stumped. Anyone got any ideas?