I think the bernina gears are nylon, I work at a St Vincents thrift shp, I clean up the machines I am not a tech but they come in dirty and the bobbin sometimes needs the screw loosend or tightened,Many of the problems are with the plastic gears,or just plain need a small amount of oil,the manuals tell you where and how much to oil. After 25 years when the warrenty is up some of the machines quit working because the plastic gears break, I have never had a Bernina and very few Huskys or Vickings come in at any age, BUT I get many of the walmart singers and brothers, cheap plastic machines don't last long , :thumbup: