Answering question for 1/4" Plug - Straight, Used with F-Cap on Fender amps

Product:
1/4" Plug - Straight, Used with F-Cap on Fender amps

Question:
I've had trouble soldering speaker wires onto this plug (I've ruined a couple so far) The shaft is not integral to the bell portion (you can spin it) If I use enough heat on the bell to solder the black wire it melts the plastic insulation and the shaft gets loose and makes intermittent connection to ground. Is there a trick to this?