Speaking from experience the other day. My friend bought an old singer to be repaired. She had attached two very old wooden spools of thread. As I was trying to make the machine sew these threads frayed, shredded and broke. Eventually got the machine working, all settings were wrong and the needle not in the machine correctly. She had lent it to a non sewer who obviously fiddled. I would definitely through or keep for display but not use an old thread.