I have 8.
It all started with one I bought in the mid 80's, mechanical, and as I requested at the time, no computer.
They don't make parts for this machine anymore, so as I find one cheap, I buy it for parts, and for my daughter if her cheapo Singer dies
All the ones I have bought use the same bobbin, same feet, same foot pedal, so I do change them periodically to keep their innerds moving