With threads, the larger the number used in reference to size, the smaller the thread. In matching threads to needles, it is good to see what the thread manufacturer recommends. I use 90/14 Topstitch needles for most quilting, except with silk.
My Thread SamplerSILK
Yes, silk! 100 weight silk (I use YLI) is great for mini-micro quilting. Many quilters use this for hand-applique but this thread in all it's colors (and strength) makes great quilting thread too. Silk really sinks into your quilt-top, showing beautiful texture. The drawback is price. It is quite expensive, but well worth it for an heirloom project. With the 100 wt silk, a 60/8 needle is good. If you are using a fine thread, then you probably do not want a large needle hole.
It's not just for bobbins anymore! I really like bobbin thread, it is generally 60 wt, meaning you get more on a bobbin! While there are many brands available, YLI Soft-Touch is what I can get locally. It is a long-staple cotton thread that is also good for piecing (use it in the top & bobbin) if you really want your seams super-flat.
50 WT THREAD
Aurifil Mako is a popular 50/2 cotton thread. I also like Affinity/Exquisite 50/3 cotton, but I believe that has been discontinued. Too bad, as I like using it for piecing and quilting. I do piece with the Aurifil Mako, but I am not fond of it for quilting (unlike many on-line quilters!).
40 WT THREADS
In my tool box, there are currently 6 different 40 wt threads. This is a good thread size (in both cotton and polyester) for quilting. The YLI 40/3 Machine Quilting thread is flawless. I have never had a problem with this thread, no breaks, shreds or knots! I love the Grey-011 and use it 80% of the time for quilting. Both the solid and the variegate colors are vivid, and there are a lot of them! King Tut 40/3 is another favorite of mine, but they are not as common near me, so I buy them when I see them. This thread is also flawless for me. These cotton threads lay on top of the quilt when I use them, but depending on the color, they can either blend in with the fabrics or stand out.
In polyesters I have both Isacord and PolyX 40 wt threads. I love the range of colors and the subtle sheen they provide. Yes, they are generally marketed for embroidery, but they are super strong and quilt beautifully for me. Signature TEX 40 cotton is also in rotation for quilting. I love the color "Pearl" it is a soft gray that blends well with a variety of fabrics. The polyester threads add a luster as these threads are shinier than cotton, but being filament fibers, they do not stand out on top of the fabric. Given this size, you can chose wild colors for quilting to cast the shade of your quilt if desired.
A big difference between the cotton and polyester threads in this size is the amount of thread build up if quilting dense designs or feathers.
And my new addition: 12 WT Sulky
This is a mercerized cotton thread. "Mercerized" means it has gone through a chemical and heat process to make it shinier than normal cotton. The size of this thread also makes the twist of the thread more visible and this yarn emphasizes quilting stitches.
Next up: My Thread Sampler