If you have a Sears close by go get a great Kenmore machine right now! There are many versions to choose from. The monthly payments for Sears are very inexpensive. I got to sew on the top of the line Kenmore and it sews great. It will be my next new machine if I need to get one. I have a Janome and I use all kinds of threads, no problem. If the bottom tension is messing up it's the top tension that is out of sorts. Be sure the bobbin thread is winding off the bobbin in the right direction too.