I started a quilting project (currently a UFO) right when I got my new sewing machine and I don't recall if I used my old machine or my new machine on the project. After pulling out the project, I see that I have a full bobbin left. A comparison of machine bobbins looks the same but I know one is for a Kenmore and the other for a Brother.

If I accidently use the bobbin for the old machine in my new machine, what will happen?

It probably won't stitch correctly.

Kat

I have swapped bobbins before and they ended up being the same bobbin size (standard). But if its not the right one its just not going to sew right, might not even fit in the bobbin case.

Maybe they use the same bobbin?

To avoid possible problems just wind the full bobbin onto a bobbin that you know goes into your machine.

mltquilt

My machines can't all take the same bobbins.
I have ended up with awful stitches when I have switched them. :D:D:D

some bobbins are interchangeable some are not- you can put it in the machine and carefully lower your needle and see if it hits the bobbin or not- if not then stitch a test piece. we have a box of bobbins that work in 4 different brand machines interchangably- and then i have my viking that only accepts a viking bobbin- period...
doesn't hurt to try as long as you do it carefully.

ditto to the above ... not all are the same.

And you will find some that look alike ... and there is an ever-so-slight difference between the two.

Rather than having a problem, why don't you transfer the thread from that bobbin onto one you know is the right one for your machine. I'd sooner do that.... than to create a problem by not doing so.

I have a Singer, a Brother and my new Janome. All three take different bobbins. The Singer looks different than the other two, but the Brother and Janome look alike. I haven't tried to see if they will work. I am afraid I'd ruin my machines.

Both my Janome 6600p and Brother Disney take the same bobbins so I do not have a problem with them.