FrankenPfaff breaking thread
 

I have the most janky quilting rig ever. My new-to-me machine is an old industrial Pfaff 463, but modified for free motion quilting. No feed dogs, and a motor bolted onto the back with a dimmer switch (not kidding) for speed control. We have been calling her Ermingerd, the FrankenPfaff.

Anyway - she makes a seriously beautiful stitch, but I'm trying my first quilt on her, and she keeps breaking thread. After re-threading, correcting upper tension issues (just guessing it's my 3 year old who cranked the dial up to 100 - there's no stop, of course...) and changing needles, I have been able to quilt at very low speed for about a minute before the thread breaks. So now I'm wondering how much of it is the thread. I'm using Robison Anton rayon embroidery thread that's forever old. I'm just guessing I bought it about 12 years ago? (Sheesh. THAT dates me, I think...) Also had some issues winding the bobbin, and it might be too loose on the spindle - not sure if that could be causing trouble as well. But when I pull the bobbin thread it seems to move freely with reasonable "drag".

Any ideas?

Rayon thread break easy. It very well could be the thread. Trying using sewing thread instead of embroidery thread.

You could try a different machine if you have something to choose from. Like nabobw says, rayon tend to break more easily, but you should be able to stitch with it. Be very fuzzy about needle (large enough or just a bit larger than strictly necessary). I have managed to free motion and top stitch on an vintage singer with shiny rayon thread, it's a very basic straight stitcher (201), and I imagine any machine should be up to it.

OK, tried a different thread and it seemed to work fine. (Although I left the rayon in the bobbin. Wonder why it's fine there but breaks in the upper?)

I'm sorry, I have no help for you but just had to open a thread with "FrankenPfaff" in the title :D

The upper thread endures a lot more "abuse" going through it's path than the bottom. It goes through a lot of guides, gets rubbed and tugged at with the takeup lever, and goes through the fabric several times before it finally forms a stitch. The bobbin thread has it much easier - very short path, no friction except in the tension assembly, no passing through the fabric. That's why if thread is breaking, it's pretty much always the top thread.

Rayon thread is notoriously weak thread and shouldn't be used for quilting. Laying the completed quilt on a bed and sitting on it is enough stress to break the thread.

The rayon in your bobbin isn't breaking when quilting because there is no where near the stress on it as is on the top thread but it can easily break once the quilt is completed and slightest bit of stress is put on the quilt, even the weight of washing it. I would strongly recommend you replace the bobbin thread with either cotton or polyester thread. It would be a shame to have all the work in a completed quilt only to have the quilting threads break from normal use.

Also, I am wondering if you have the top thread sitting vertical or horizontal? Or do you have it on a thread stand behind your machine? Superior Threads has a video and explanation why you use one direction over the other. Depending of the type of thread on the spool determines the way it should be on the machine. I use rayon for my embroidery machine and it has to be on the horizontal thread holder.

I agree with switching out the bobbin thread too. Rayon is too weak for quilting.