Why Is My Thread Tangling Like That? Choosing the Right Thread for Your Vintage Sewing Machine
Do you end up with a tangled mess of thread under your spool when you sew with your vintage sewing machine? This may be because of the type of thread you're using and the kind of spool pin your vintage machine has.
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Stacked vs. Cross Wound Thread
You may need to use stacked thread rather than cross wound thread. I'm using variegated thread so you can see the difference more clearly. The spool on the left is stacked. The thread is wound onto the spool in parallel rows--each row stacked on top of the next. The thread on the right is cross wound. It's wound onto the spool in a crisscross pattern, overlapping itself. Heirloom Creations has a good overview of the differences between these two kinds of thread
Vertical vs. Horizontal Spool Pins
Stacked thread should be used on a vertical spool pin, which is what most vintage sewing machines have. Cross wound thread should be used on a horizontal spool pin, which is what most modern machines have. This has to do with how the spool unfurls while sewing. The stacked thread will turn to allow more thread to travel to the needle, while the cross wound thread doesn't turn--the thread is just drawn off the spool without turning it. My modern Singer 7256 Fashion Mate has both kinds of spool pins.
Solutions for Vintage Sewing Machines
However, when you put your cross wound thread on a vertical spool pin, the machine has to turn the spool to unfurl the thread, and it can tangle underneath the spool. This tangle can cause the thread to draw taught, which can snap your needle as it tries to pull more thread but can't.
You can use a spool cap, thread stand, or spool pin adaptor to make it easier to use cross wound thread on a vertical spool pin, or you can just buy stacked thread for your vintage machine. Coats and Clark Dual Duty Thread is a good choice for all purpose stacked thread (the variegated thread below is Coats and Clark Dual Duty). Gutermann thread tends to be cross wound, so stay away from it for your vintage machine, unless you plan to use a spool pin, etc. Unfortunately, I've found that Gutermann is too tall to allow for a spool cap on most vintage sewing machines.