Originally Posted by
sewbeadit
When they first came out with the nylon thread they recommended to not use it in the bobbin area because it could damage the machine. Is that not the case now?
It probably depends on the quality of the thread. When it first came out, nylon thread closely resembled fishing line. The type of nylon thread I use (YLI monofilament) is about .003mm diameter and about as fine as a fine strand of hair. I do think there are some sewing machines -- especially those with plastic bobbin cases in addition to plastic bobbins -- that might wear out faster from using a lot of nylon monofilament, but most machines (including vintage) can handle it just fine.