The Singer "Featherweight" model 221 is probably one of the most popular and sought after "Vintage" sewing machines in the history of machine sewing. Due to it's light weight, cast aluminum frame, it can be rather fragile. Recently, I had to repair a broken thread spool pin. The original design has the spool pin permanately pressed into the top cap. This one was totally gone. Snapped right off..... I had some new "threaded" pins and found a hex nut to screw on just far enough to provide a lip for gluing.
I had to do some prep work with the dremmel tool grinding wheel so the nut would lay flat against the inside of the top cap. I also had to drill the original pin hole out to a slightly larger diameter.
I used Gorilla Glue. It worked great.
It came out looking as good as new. I can't even tell that it was repaired.