The 12 weight wool ( thread) is usually used for wool hand appliqué. It is not made to go through a machine. That doesn’t mean you can’t- if you get a really big needle ( our usual machine needles are for 40,50,60 weight threads- you are trying to put a Much thicker, heavier thread into your needle- you need a needle for 12 weight threads) then you would need to really work at your tension, loosen it so the thread is not being shredded in the tension disks. It probably could be done. You may waste a lot of your thread trying to get everything correct though. It’s made for hand work- we use chenille needles or large embroidery needles when using it.