I have a Singer bobbin winder. I have a lot of problems with it . It sometimes winds too loosely or winds at bottom and not at top, so it's uneven. I don't like it at all. I wasted $30.00 at Joanne's.

We have to watch how ours threads. I usually keep the little scissors handy to guide the thread so it fills the bobbin evenly. I have to do that one many of our machines so that's no big deal to me.
The bobbin winder is still a lot more convenient than the machine.

Joe