I piece with thin thread in top and bobbin. I like a size 70 or 80 in the bobbin and size 50 2 ply in the top. I usually use poly for for the bobbin, don't care if it is poly or cotton for the top. If I use a size 50 3 ply for the top, I use the thinnest thread I can find for the bobbin. I have Aurifil size 80 which is excellent and so is Invisfill. Connecting Threads Pro on the cone is size 70. For machine quilting I use whatever I like and just be sure the needle is the correct size for the type of thread.