I've always used a plastic bobbin for a drop in bobbin. If the machine has a metal bobbin case and usually goes underneith the throat plate I use a spoked metal bobbin.

Does it matter?

ty
simple quilter

Interesting question, I've never used plastic bobbins - I don't know if they make them for my machines

It depends on the machine but yes, it can make a difference.

what i've always been told is you can use a plastic bobbin as a substitute for metal but not metal for plastic. Now i don't know if this is actually true, but it's what i've been told in the past.

All the bobbins I use for a bobbin case are metal. I use plastic for the drop in bobbins.

Whatever bobbin was made for the machine

Our local Janome repairman, an older experienced guy, tells us that plastic bobbins are weighted perfectly for Janomes, where metal are not.

Jan in VA

And not all plastic bobbins work in a Janome ... you need a Janome one.

I just use the bobbins that are made for the machine.

I have two machines, one with a drop in bobbin and one with a front bobbin and they both use plastic.

I was helping a new sewer at quilting one time and she was having a terrible time with her tension and I discovered she was using a mix of bobbins. When she used the bobbins that were meant for her machine she didn't have any problems at all.