Cari-in-Oly,
Thank's for the 401 assembly chart. I added it to my fix-it folder.
.................................................. ....
My wife has dozens and dozens of cone thread of many different kinds. Mostly serger thread, but some other types too. I use it a lot. And to date I've not had any of it twist and bind up the machine.
We have a 401 and I have used the cone thread on it a lot. So I'm going to be the one that says that the problem is probably not the thread or the way it spirals off the cone, but most likely a top tension or thread path issue.
I'm going to show some pics of our 401 and the cone thread set up I use.
Here is the set up I used on the 401 and many of our other machines with zero twisting of the thread:
The thread comes off the spool up through the hook at the top, through the spiral spring at the top of the widget then through the normal thread guides and tension. Works perfectly. No twisting or binding of any kind. I've have used this method to quilt several quilts and from start to finish of the bobbin there's been no twisting.
Here's a pic of my multiple thread set up:
This is threaded exactly as above only with three lines of thread from cones.
The spring at the top of the widget actually twisted the three threads into a
spiral and it fed through the guides and tension perfectly. No binding at all.
It the above pics I was using the patterns to decorate some of the squares I used in my All Machines Denim quilt. If the thread coming off the cones would cause a problem, it would have. But it didn't.
This is why I said it's probably a tension problem. Miriam and some of the
other posters have alluded to this as well.
Now here is another thing I found on our 401a. The top tension would not hold it's setting. I kept having to adjust it until it quilt adjusting. So at that point I took it out of the machine for a complete tear down and cleaning. When I did this I found a bunch of metal filings in the set screw hole between the set screw and the tension body.
What this was doing was jamming the top tension set screw to the point it couldn't hold the tension assembly in place. So as we were sewing the top tension was working it's way out of the machine body.
Once the metal fragments was removed and the tension cleaned and adjusted this machine has worked perfectly.
Just some ideas, but I'd start with the tension and thread paths were that my machine.
Joe