The HIGHER the thread weight the THINNER the thread, and vice versa. A higher thread weight has a finer gauge. A higher PLY number means more strands of thread are twisted together so the thread is stronger. A general purpose medium weight thread is 40wt or 50wt.
A 30 weight thread is heavier than a 50 weight because it is denser and takes only 30 kilometers to equal one kilogram compared to 50. – The fraction on the thread spool tells you the weight and the number of plies or strands twisted together (for instance, 60/2 is 60 weight thread with 2 plies).
When discussing weight of thread, the smaller the number, the thicker the thread. The weight is determined by how many meters of thread it takes for a skein to weigh one kilogram. In this case, the 40 wt thread is slightly thicker (heavier) than the 50 wt thread.
cotton thread for quilting projects. Higher quality 50 wt. threads offer a nice thin thread that won't add a lot of bulk to seams when piecing a quilt. They are also ideal for machine quilting, appliqué, hand piecing, and hand appliqué.
A thread is labeled 40 wt. when 40 kilometers of that thread weighs 1 kilogram. A 30 wt. thread is heavier because it takes only 30 kilometers of thread to weigh one kilogram.
It works great for top-stitching as it is a more noticeable stitch. This thick thread covers large areas faster with less stitches than a 40 weight thread. It therefore requires a larger needle and more machine tension. Use 30 weight for decorative stitches or to completely fill in your embroidery designs.
40wt is a thread that is significantly heavier than 60wt, and noticeably heavier than the 50wt. While it is always good to have different size threads on hand, just in case, I don't usually sew on heavy fabrics, but I do consider the 40wt thread essential for my sewing stash.
50wt Aurifil thread can be used for machine piecing, hand piecing, machine applique, hand needle turned applique, fine needlework, foundation piecing, miniature patchwork, detailed quilting, bobbin lace making, and machine embroidery.
These are the types of threads that you will most frequently find, most often 40 or 50wt. They can be used for most construction, quilting, machine embroidery, sergers, and general purpose sewing. Medium weight threads can be made from all types of materials including cotton, polyester, rayon, and even metallic.
Needle size is determined by the weight of the thread.
It is helpful to remember that a 50 weight thread should be paired with a size 80/12 needle. (80 is the European size, while 12 is the American needle numbering system.)
Gutermann Cotton Sewing Thread is a fine 50 weight cotton thread but strong with a silky finish for users who prefer to sew with cotton.
Sew-all Thread is designed to handle all demands. A fine 50 weight cotton thread but strong with a silky finish for those who prefer to sew with cotton. Suitable for hand or machine sewing, Gutermann Cotton Thread is a 100% longstaple mercerized cotton sewing thread.
The three most common sizes of thread in the U.S. are 30, 40, and 50 wt. (For comparison, all-purpose thread is usually 40 wt.) It's best to know your project and possible strain on the seams before choosing a thread.
Thread Weight
Heavier weight threads are more noticeable when they are used for quilting. A 40 weight thread is a popular choice for quilting while 30 weight threads are more visible. Lighter 50 weight threads usually blend into the fabric.
With a high strength to weight ratio, nylon is one of the strongest threads available, making it a great choice for stitching upholstery, leather, and vinyl. This bonded 3-ply nylon thread has been specially treated to decrease friction while sewing at high speeds, resulting in smooth stitches.
In the world of thread, higher numbers mean thinner thread. So 80 wt. is thinner than 50 wt. (which is the most common sewing thread). You might think that thin thread would be weak, but Aurifil 80 wt. is thin and strong!
Kimono Silk
100 wt./2-ply filament silk thread. Designed for quilting, applique, and binding. Kimono Silk is incredibly smooth and strong, especially considering its fine diameter. A favorite for binding quilts, by hand or machine.
Perfect for use as hand sewing thread, or quilting thread!
40 weight thread can be used for free-motion techniques, appliqué, garment construction, quilting, tacking…the list goes on! 40 weight thread can also be used in partnership with other threads.
Tex 70 is the heaviest commercial size recommended for home sewing machines. Heavier threads make your stitching more visible. The thread size measures the thread's thickness. If another weight is given for thread (like ounces), it refers to the amount of thread on the spool.
Thicker thread should require more tension to avoid puckering lightweight fabrics, but this is often just what you need to avoid issues. A heavier thread in the top and bottom will increase both tensions, and you'll probably need to set a lighter tension to accommodate heavyweight fabrics.
Kevlar® is one of the thinnest, strongest threads available on the market today. Because it's so thin, you can easily sew things together using Kevlar® thread without causing any damage or ripping apart your fabric.