I am using 100% cotton Gutterman thread and it keeps breaking - is it the tension on my machine, poor quality thread or stale thread??? I use Gutterman all the time for piecing and never have any problems until this colour!

I've run across thread before that was like dry rot and broke easy....could be the problem.

I find on my machine its the tension. Sometimes its a different weight, your machine is off slightly.. if you switch the thread and try a new one on a sample piece of fabric are youhaving the same trouble? if so its tension usually. also even the same thread comes in different weights .. is the bobbin thread the same as the top thread?

Could be the needle. I have had it be something as stupid as the size of thread in the bobbin. Tension. Bad thread. The possibilities are endless.

I once put a new needle in backwards, yep, backwards....and the thread was new, the tension was ok, but I couldn't go a dozen stitches and the thread would break. Look at the thread.....is it frayed at the breaking point? If so, I would think it is the needle causing the problem.

Well I have sewn continuously for the past 2 hours and it hasnt broken again - I was thinking it may have been the thread - stale at the start of the reel...

If you have used this thread with no problems before I would guess it is the spool of thread.

I can't think of the name now but i have a little bottle of liquid that i put on a spool of thread if it's rather dry. sewers ease or something like that. helps.

Could be tension, could be that you need a new needle, could be the thread, could be too much lint around the bobbin carrier. Does that help? :D :D

The process of elimination LMBO I have found bad spots in a spool... I have taken off several yards, retried and it worked great :D:D:D
I am glad that whatever the reason was, you are happily sewing again :D:D:D