I've been told to use metal bobbins in my vintage machines that have metal bobbin cases and the plastic in newer machines with plastic cases. Basically use what was supposed to go in there when they were made.

I do only use the metal bobbins in my vintage machines, but am seeing more and more vintage machines sold with plastic bobbins in them. I'm just wondering why? I've been told using the plastic in metal cases can affect tension and cause problems. With both plastic and metal still so readily available, why would someone put plastic bobbins in these old machines?

Knowledge? They probably don't know, don't understand and most importantly don't care. :)

I am not sure, maybe with all of the prewounds available?
I prefer the metal and wish the new machines still used them :D:D:D

Some of my old machines don't seem to care what kind of bobbins I put into them.

I can even use the very cheap pre-wound plastic bobbins in my 15's - though the machines do seem like the heavy solid metal bobbins best of all.

When the plastic bobbins came out in the 60's, they were sold as replacements for the metal ones. I used them in my grandmother's 401 and they worked just fine, so I never gave it another thought.

Since I started collecting vintage machines a few years ago, I've had a couple of slants that didn't like the plastic bobbins, but the rest haven't seemed to know the difference.

I wouldn't try the reverse, though - I wouldn't use a metal bobbin in a modern machine designed for plastic bobbins.

I agree!

I'm guessing that part of the reason is that the plastic bobbins are much more readily available in places like Wal-Mart which would be where a person would most likely go first to find replacement bobbins.

Even as an experienced seamstress I did not initially recognize the differences between the various bobbins and attempted to use wrong ones on one of my machines and did not realize that was part of the cause of the birdnests I experienced with it. Need to go back and figure out which bobbin really was meant for that machine and see if that will make it work right. Also need a bobbin cover for it. The random piece of clear plastic does not substitute very well there either.

The plastic bobbins were manufactured and sold as replacements for the class 66 bobbins in the 60's.

Clearly the Singer Company thought they would be all right.

And they're still being sold as class 66 bobbins.

If there were something wrong with using them on a machine made for class 66 bobbins, wouldn't Singer have re-classed the plastic ones or maybe put a disclaimer on their current packaging by now? "Not to be used in machines made prior to 1960" or something like that?

For best results use the bobbins that the manufacture of you machine recommends. If they are for vintage machines then you may have to contact manufacturer or check on line for correct ones. I tried using #15 in my singer but #15j was recommended and it seemed to fix fine but was actually a bit smaller and would jump out of the case causing problems.

They probably are using what they have on hand. I agree, metal in metal, plastic in plastic

I really wish bobbins had some sort of labeling on them so I would know which one is which.