Are these prewound bobbins?
 

These came in a bunch of stuff from a sewing machine drawer. I have never seen anything like this but I wonder if these are prewound bobbins. The bobbin seems to be a rigid type of cardboard.

yes they are

They are, but I would test them for thread strength and make sure the spool is still viable. Cardboard can dry out just like paper and become brittle.

I usually buy the plastic prewounds, but when there's a great deal on the paper ones, they often include instructions to tear away the top cover. I guess it is to see how much thread remains. It has worked fr me.

I take the paper/cardboard sides off pre wounds. It's there to keep the bobbins from getting misshapen, not needed in the bobbin case. But it's okay to leave it on if it doesn't cause a problem.

I never thought of taking the paper off the pre wounds bobbins. Does it not mess up the thread? I would think the thread would unwind on the sides. Learn something new all the time on this board.

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*** They look like the bobbins that are used in a sewing room and the thread is usually heavier.
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I never heard to take the sides off either. So far (knock on wood) I haven't had a problem with them in the long arm OR embroidery machine. I really do learn something new here everyday

Why not just rewind them onto your own bobbins if you are unsure of the 'viability' of the bobbins?? :rolleyes:

Superior has excellent educational articles about thread and bobbins.
A few facts about pre wounds:
http://www.superiorthreads.com/educa...acts-and-faqs/

And there is a top and bottom side of prewound bobbins.