I have been using Aurifil 50wt 2-ply for piecing and love it, but Aurifil is a bit pricey.
Just bought a cone of Threadart bobbin thread 60wt from Amazon, and it's a lot less expensive. It's finer than the Aurifil, but seems plenty strong when I hold it in two hands and try to break it. Was thinking of using this in the bobbin and Aurifil on top. That way the bobbin would hold more thread and not run out as fast, plus it would be cheaper than using all Aurifil. Now I am thinking maybe I should use the bobbin thread on top too and make it *really* cheap!
If I am remembering correctly, some people use So Fine! both top and bobbin for piecing. I'm thinking the Threadart 60wt would be similar.
Any thoughts? Oh, and here is a link to the Threadart stuff I bought:
http://www.amazon.com/Bobbin-Thread-...dp/B0034W118Q/