set both tensions about same,try a test sew,if the top thread is being pulled through,loosen the bottom or tighten the top,take away from peter to give it paul,and vice versa....
I found this in my old notes and thought it may help others.
How to adjust for correct tension when sewing.
In the picture below you can see how I do this. I simply run a triple stitch up the scrap of sail cloth, with the correct number of layers.
As the stitch runs, I stop and change the tension setting and number the area with a felt pen, according to the tension setting. after checking the stitch, I can then adjust the top or bottom tensions to suit the number of layers that I'm stitching.
This works really well for me on my wife's domestic machine.
I have found the "industrial machines", are no where as critical with their tensions.
This ad on gumtree Western Australia made me laugh as well. An extension.........Up there for thinking.
Only $130.00 as well.
http://www.gumtree.com.au/s-ad/dianella/other-tools-diy/seewing-machine/1039234680