Bobbin Thread Breaking
 

I am quilting on a Little Gracie Frame with a Janome 1600 PDB. I think it's a B, lol. It quilted fine to do the one border. Ran out of bobbin thread. Replaced it, now it will only quilt for a few seconds and the bobbin thread breaks. Changed bobbins, same thing. Oiled, cleaned etc. same thing. So I adjusted my tension on the bobbin case, it became really loose. As I was pulling while it was loose, the thread tightened up and broke. Tried again, it was supper loose, pulled about a yard out and it got real tight and broke. What causes this? Do these cases go bad?

Check very carefully to see if you have a bit of thread caught in the bobbin case or in the area where the case goes. Also be sure the bobbin is not filled over its capacity.

Did you try re-threading your whole machine? Sometimes that helps.

Try with a different spool of thread too? Might be a bad section of the spool?

I am actually sitting here in the l.r. With the bobbin and bobbin case in my hand. It is no where near my machine. So it isn't the machine. The metal thing the bobbin goes in, is what I am calling the case, not sure of that is right or not. The bobbin is over half way empty because I keep pulling and breaking the thread. It is weird.

Change the needle, look for heavy lint or thread in the bobbin case or bobbin area, rethread the bobbin and machine with a different thread, adjust tension on the bobbin case. Hope this helps

if its a metal bobbin it could be warped. almost sounds like its snagging on something in the case.

Yes. What you have in your hand is called the bobbin case. There's a spring that the thread goes under. Check this area for lint. When the thread breaks, what exactly happens? Pull the thread until it starts to get tight, but before it breaks and see if you can figure out exactly what is catching the thread. Does it look like the thread just gets caught under the spring? Another thing that snaps the thread is backlash. The thread gets wrapped around the spindle in the bobbin case.

This is when a bright light and strong magnifying glass are must haves.

Have you tried a completely different bobbin? I have one metal bobbin that looks exactly like all the rest, and my machine does not like it, it makes a horrible noise. I have a friend who dropped one of her bobbins and must have put in a microscopic dent in it somewhere.