I use a 600 almost daily, runs like a John Deere tractor. Bought it used from thrift shop for about $30 about 10 years ago--best money I have ever spent. Hubs takes it outside to clean and oil about every 6 months--love my machine ! Yes, no plastic gears on machine. You might try to remove all the bobbin area, clean, and make a few adjustments. also I find some of the bobbins to be troublesome. Before I load bobbin I take it apart and the screw it back together but not very tight.