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Selecting the Right Thread For Your Project

Selecting the Right Thread For Your Project

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Selecting the Right Thread For Your Project

If you’ve been to a fabric and sewing shop lately, you’ve probably noticed there are a lot of different threads out there. The choices can be overwhelming, especially if you are just getting started as a sewer.  So here’s a quick guide to selecting the right thread for your sewing project.

Thread Gauge

General use threads come in a variety of different colors and fibers.  Within each of these categories, you will find threads of different gauges. When selecting the thread for your project, it is important to select the gauge that fits the task.

How to Find the Gauge

Spools of thread display the weight and ply count on the end label.  The two numbers will be written as a ratio.  So for instance, a 30 weight thread with three strands twisted together will be labeled as 30/3. Many American manufacturers only label their threads with the weight, so you may not always be able to determine the thread’s ply. The thread’s “weight” is actually its linear density or the length of thread in kilometers required to weigh one kilogram.  Thus, the more length it takes to reach 1 kilogram in weight, the finer the thread.

This means that when you are reading the thread’s label, a higher weight number means a fine, thin thread. In general, you will use 30 weight or higher for machine sewing.  A 20 weight thread would be used for thick fabrics, such as denim or upholstery.

Alternate Gauges

Other common measurements used for thread include the Tex (T), which indicates the weight in grams of 1,000 meters of thread. When this measurement is used, a higher tex means a thicker thread.  So its numbers have the opposite of the American style weight measurement.

The two other measurements you may see for thread gauge are the Denier Count, labeled Td or d, and commercial sizes, labeled with a V.  Like the tex, deniers increase with the thickness of the thread.  Nylon fabrics are sometimes described in terms of the denier weight of the threads used in their weave.  Commercial size thread is most often used for heavy weight fabrics and upholstery.  Outdoor and marine threads are often described using commercial size.

The commercial weight is actually the denier weight divided by 10.  So, a 300 denier thread is the same weight as a V-30 thread.

Plies and Twist

The plies of a thread indicate the number of strands twisted together to create a single thread.  Plying single strands of fiber together gives the final thread added strength, similar to using multiple strands of twine to create a strong rope.  Most threads use three or two plies to create the final thread. Some thread labels may indicate the twist, or how tightly the strands are wound together.  A tight twist will be smoother and stronger than a low twist thread.

Fiber Content

Thread can come in any number of single fibers and fiber combinations from the simple cotton to the man-made metallic.  The fiber of a thread is the actual material used to make it.  Cotton is the most typically used natural fiber. While commonly selected synthetic fibers include nylon and polyester.

Natural Fibers

Natural fibers will vary in length and quality depending on their source. For instance, a low-quality cotton will have short fibers that appear as fuzz along the threads length.  When longer cotton fibers are twisted tougher, there are few of these ends appearing.  Quality silk fibers are long unbroken strands of natural filament unwound from the silk worm’s cocoon. A lesser quality silk will make use the of broken fibers.

Most cotton threads available now are mercerized.  That means the threads have been chemically treated add smoothness and shine.  Mercerized cotton is stronger but loses most of its natural stretch during the mercerization process.  Your mercerized cotton thread will be strong and heat resistant, but not offer much ‘give’ to your garment’s seams.

Synthetic Fibers

Man-made fibers are produced using a chemical process.  Viscous liquid is extruded and stretched to create long strands.  The fibers are thus long and consistent in size.  Multiple strands are twisted together to make the synthetic thread.  The quality of man-made fibers is dependent upon the quality of the materials and processes used to make the fiber.

Among the synthetic threads, polyester is most suitable for a range of fabrics.  Polyester retains some stretch and works well with knit fabrics.  A blend of cotton and polyester will offer the stretch of the synthetic and the strength of the cotton.

Nylon threads serve a limited purpose as they tend to be heat sensitive and become brittle over time.  Nylon can be used to produce a clear thread, so it is sometimes selected despite its limitations when invisible thread is needed.


  • You shouldn’t use thread thicker than V-69, or a weight of 14 on most home sewing machines. If you are using a particularly lightweight machine, you should check the manufacturer’s specifications with regard to the threads that may be safely used.
  • Whenever you switch thread weights, you may also need to switch the tension on your sewing machine or use a different needle. For instance, the Coat and Clark website recommends that you use a machine needle size 16-18 and lengthen your stitches if you are sewing with their 12 weight outdoor upholstery thread.
  • If you are just getting started machine sewing, I recommend that you buy a medium weight (50) thread for all your projects so you don’t have to worry about needle size or tension. Of course, you may need to make adjustments to suit your fabric.
  • Look for a thread that has a nice twist. A low twist thread is more suitable for hand-stitching.  If you tug on the thread and it comes apart, it is not going to hold up for your machine. Single ply threads may be very fine, but they may also snap easily depending on the fiber used.  Save these specialty threads for special projects.
  • When choosing a fiber for your thread, it is best to try to match your fabric. Different fibers behave differently when exposed to heat and moisture and have different strengths.  A well-matched thread and fabric will help reduce the chances of your fabric puckering or your thread fraying over time.

Select a thread color that is just slightly darker than your fabric and enjoy your new hobby.

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