I have what is probably a really silly question, but I guess if you don't know..... I want to get new needles for my machine (brother) and need to know what size all of you use for piecing and quilting. Is the size needed based on thread size? or based on purpose like fmq or piecing? Is there one size that works for everything?

Check out Superior Threads website. They have an in depth tute on needles and threads.

Choose the thread size for the effect you want or to suit the purpose of the stitches, and then match the needle size to the thread size.

For piecing, many people like to use finer threads - 50 or 60 or even 70 wt, so they will need a smaller needle - size 12, 11, 10 or 9.

For quilting, you might want to use a 30 wt thread - a size 16 or 18 needle. Or an even larger thread, which will need an even larger needle.

Too large a needle for the thread and the needle may not be able to create a thread loop for the hook to catch - skipped stitches.

Too small a needle for the thread and the thread will shred or break.

You may need to try a few different needle sizes to find the one that gives you the perfect stitch for that combination of threads, fabrics and stitching. :)

Per tech where I bought machines I use a 12 to piece and a 16 (poly) or 18 (cotton) to FMQ

I buy Schmetz needles and buy specific ones for denim, quilting, embroidery, sharps and then universal for everything else. I tend to use 12 for piecing.

good topic, I was wondering the same thing.
I want to get one of those double needle things, the one that has the double needle, single shaft. (twin needle I think it is called)

Don't you have to match the thread and needle to the fabric?

Sort of. The regular weight sewing/piecing thread can handle a range of needle sizes. Cotton fabric is also very forgiving and can handle a variety of needle sizes. It gets tricky when you use thicker thread or specialty thread or fancy fabric.

I usually piece with (what I happen to have in the machine, cough cough) 75 or 80. For quilting I use a 80 or 90. Often I use the same thread (weight, not color) for the piecing and quilting.