I have read both ways, but for piecing and probably quilting, I have read here to put 50 weight thread in bobbin, don't remember exactly why, but more will go onto bobbin, for one thing. Other places I have read where top and bobbin thread must match in weight and "material", i.e., cotton vs. cotton wrapped poly, etc. Opinions?

I use pre-wound bobbins for embroidery machines for piecing. Lots of thread on the bobbin to keep me going.

Short answer is no, they don't have to match.

I usually use a thread made for bobbins, like Decobob or BottomLine, which are 60 weight and my thread of choice in the top.

https://www.superiorthreads.com/bobbin-thread

Watson

Doesn't matter, the machine doesn't care one way or the other. It's our thinking that makes it complicated. I use thin thread in bobbin, at least 60wt. The new thin threads are strong.

Wow, my ignorance on things sewing abounds, even after more than 60 years' experience! I just bought some Aurofil 50 weight cotton for bobbins, so apparently what I have been using is 40 weight ordinary thread? And now I hear 60 weight is even better? Yikes, there's always more to learn (for example, it was only a couple of years ago that I found out there were different size needles. . .). I must be a senior member based on age, not skill!

I am so happy to see the responses to this post. It certainly makes things more clear for me. Thank you.

I piece with 50 wt and most often use the same thread in the bobbin, just because that is the way I always did it. My machine doesn't really care.

I don't pay a lot of attention to that. It seems to work just fine either way. It is a good way to use up odds and ends of thread both on the spool and in bobbins. I often use a bobbin as my top thread on a vertical spool. I figure the more economical I am with thread the more money I have for fabric!

What ever I put in my top, I put in my bobbin. I don't want to have to worry about it. My machine tells me when I'm running low and is easy to change. I try to do extra bobbins when needed but my machine will wind them while its still threaded. I love Aurifil thread, I get more accurate seams using it. I do the same thing when doing embroidery. Its always the same type, depending on how much stabilizer I might be using I may have different colors as long as I'm sure it won't show thru.