Both are industrial model but the 31-15 i believe is a drop or single feed machine and the 111w models (not all but some) are compound feed machines (walking dog). Basically one feeds fabric just using the bottom plate moving the teeth, the other moves using a walking motion of the foot as well as the bottom teeth. Triple feed does both plus the needle moves with one of the dogs. My understanding is the 111ws are the OGs and everyone else copied this style of machine.
looks like the 111w can take some heavier thread as well? Not sure on the lift of the 111w. You’ll find guys on leather forums talking about the 111w because they can do thick material.
mom personally looking for a 111w or 211 unless someone has a good reason to change my mind. Hopefully we can both learn together.
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