Assume the tension has been set perfectly in the usual places, the right size needle is used for the fabric, everything is threaded properly, and all is well in machine land. I know machine repairmen have always gone to a little screw that is recessed in the body of the machine. It sits all alone. They give it a quarter turn sometimes or a half, and the problems are gone. I'm talking about problems of the bobbin stitch not matching the top stitch by either being too loose and knotting or by breaking due to too much tension. Can you help me? I would like to permanently get my machine working smoothly so I can sew without aggrivation. I just want to sew a half hour project in less than 12 hours. YA KNOW? I have 40 years experience so it's not like I don't know how to adjust it in the usual way and perform the maintnence I need to perform. I am very good with my end of the deal. I use good thread, good fabric, good needles, but I seem to have bad karma.