I use a 40wt (cotton or polyester) in my longarm. Superior Threads website has an excellent thread tutorial.

Have you checked out Superior Threads website?...

http://www.superiorthreads.com/page/330/

All I've used so far is Superior's So Fine #50 on top with Superior's Bottom Line #60 on bobbin. For now am staying with this combination because am just using STD and don't want thread visually jumping out at me. Have some Superior King Tut #40 waiting in the wings...that'll be when I want the thread to do some talking.

I want to thank you all a lot for all the input. I have used signature 40 wt and yli 40 wt. to quilt with and I would like to get something finner I want something that show the quilting but not the thread cause I'm not that good at FMQ, cause sometimes a stich is longer than the other and I don't want that to show. You all have set me stright. on what sige thread to use. I read some were that the 90wt. was good for quilting, but maybe I was wrong.

I use Isacord 40wt poly thread to FMQ or Gutterman machine quilting thread

I use either connecting thread 100% cotton or machine quilting cotton thread, I like the stitches better with the machine quilting thread. I use a DM.

are u hand quilting or machine quilting. makes a difference

I use a lot of Superior 50 wt. For most purposes it's about perfect, and with Bottom Line in the bobbin, it's closer to perfect!! :)

Here is a good article on the different kinds and sizes of threads.
http://sewhappygeek.co.uk/index.php/...anding-thread/

A quilt would surely fall apart using 90 wt. thread! Piecing is typically done with 50 or 60 wt. and quilting with 30, 40, 50 or 60 depending on the look you want.