For what it's worth, I was told by an industrial sewing machine guy that the newer machines have internal threading which creates more lint build up inside the machine. Machines that have external threading has less lint build up. The lint over time will cause the tension disc to get a groove in them causing tension problems. That is why it's important to have the internal threading machines serviced frequently to remove the lint from the tension discs that the sewer cannot see. So the less linty thread you can use for the newer machines the better.