Actually, I use 100% cotton thread to set the tensions at work. The tensions (upper and lower) are made to be adjusted. There's really no such thing as "auto tension." It's just a setting on your upper tension. The tensions that actually are controlled by the machine, just take your control away. Here's a link to how to set your tensions...
http://shesasewingmachinemechanic.bl...o-balance.html (Which will probably be deleted, because I'm not allowed to help people through my own blog. But if someone else posted my link, it would be alright. I'm not selling anything on my blog, so I don't get it.)