The hook washer as it’s called in the parts book, is the large flat washer that sits under the hook, it has like a finn that extend at 90 degrees upward just below the point of the hook.
i can’t figure out what it’s function is, but the needle is rubbing on it, and I don’t think it supposed to be this way. I’m an automotive mechanic by trade, I have no previous experience in sewing machine.
when sewing multiple layers of upholstery leather, it all goes well for about 12 inches, then my string frays and breaks. (135 thread, 160 needle, 5 stitches per inch, pressure is ok)