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| Polyester Thread Information |
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Polyester thread looks, feels, and performs like nylon thread. But, there is one important difference - polyester thread has superior resistance to sunlight (UV), mildew, and abrasion, This makes polyester thread the first choice for sewing, binding or wrapping anything that is consistently used outdoors or in moist areas. For example, you can use either nylon or polyester thread for automobile upholstery. But if your car is a convertible that is frequently driven with the top down, then you should use polyester thread.
Polyester thread has excellent resistance to mildew and aging. Its resistance to sunlight (UV) is superior to nylon. But, there may be some loss of strength with prolonged sunlight exposure. Threads like Tenara™ will do better in the outdoors than polyester, but they cost 5 to 8 times more than polyester, come in a limited number of sizes and colors, and have a plastic look. |
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Polyester is a general purpose thread that does everything well. Like nylon, there are more specialized threads that outperform it in specific areas:
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Strength-- A middleweight (Size 92) polyester thread has a tensile strength of about 15 pounds. At that strength there are very few people who can break it just by pulling. Commonly used threads such as polypropylene, spun polyester, acrylic thread, and cotton have tensile strengths ranging from 4 to 10 pounds. Kevlar is the exception with a 35 pound tensile strength. but, it costs $130.00 a pound compared to $24.00 a pound for polyester.
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Fire retardance-- Polyester thread stands up to heat but is not fire retardant.
It sticks at 440ºF and melts at 483ºF. Use our
fire retardant sewing thread,
Kevlar™, or
Nomex™ when there is a critical need to protect against heat and fire.
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Bleaches and Solvents-- Excellent resistance to bleaches and other oxidizing agents. Generally insoluble except in some pheolic compounds.
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Acids and Alkalis-- Good resistance to most mineral acids. Dissolve with partial decomposition in concentrated solutions of sulphuric acids. Good resistance to weak alkalis. Moderate resistance to strong alkalis at room temperature. Disintegrate in strong alkalis at boil.
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Mildew, Aging, and Abrasion--Not weakened by mildew, excellent resistance to aging and abrasion.
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Elasticity--Polyester thread stretches about 26%. This means that 12 inches of polyester will stretch to 15 inches over time. This is usually good because it lets your seams adjust to movement and changes in temperature. Because polyester stretches, it may not a good choice for projects involving webbing or hanging things.
Kevlar and
waxed thread are better choices.
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| Polyester Thread Uses - Here is a list of items that should be sewn with polyester thread: | | Awnings | Flags | Sails | | Backpacks | Horse tack | Saddles | | Banners (outdoor) | Laundry bags | Spa covers | | Beach chairs and umbrellas | Marine fabrics | Tarpaulins | | Boat covers and upholstery | Motorcycle seats and trim | Tents | | Canopies | Patio furniture | Umbrellas | | Canvas tops and bags | Rain gear | Vent covers | | Car and truck covers | RV covers and upholstery | Windsurfing gear | |
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Polyester Thread Sizes - Size refers to a thread's thickness--not the amount of thread on the spool. As thread size increases it affects the thread's strength, diameter, sewing machine used, Yards per pound, visibility. Here are specifications for four sizes that illustrate this point. |
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Size 33 |
Size 69 |
Size 138 |
Size 346 |
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Tensile strength increases |
3 Lbs |
11 Lbs |
21 Lbs |
53 Lbs |
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Thread diameter increases |
0.0070 In |
0.0107 In |
0.0152 In |
0.0258 |
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Yards per pound decrease |
12,200 Yards |
6,000 Yards |
3,000 Yards |
1,300 Yards |
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Sewing machine requirements increase |
Home |
Home |
Commercial |
Heavy Duty |
| Needle size increases | 12 to 14 | 16 to 18 | 20 to 22 | 26 to 28 |
| Visibility increases | Low | Unobtrusive |
Noticeable | Stands Out |
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Fabric and leather cost much more than thread. This means that you should usually select a thread size that is weaker than the material that you are sewing. Otherwise, you will be left with a great looking seam on a shredded fabric. There are two exceptions: (1) If safety is an issue both the thread and fabric should have the same strength; and (2) If you want stitching to be a focal point (e.g. sports car interiors) use a thread that is heavier than the material.
Size Guide--Use this Size Guide to identify the thread size that best meets your needs: |
| Size | Description | |
Size 15 / 23 | Ultra lightweight polyester thread used for bobbins, and sewing garments, flags, and banners. Tensile strength is 1.5 pounds for Size 15 and 2.0 pounds for size 23. Expect 30,000 Yards per pound for Size 15 and 21,000 pounds for Size 23. Inconspicuous stitching. Use with either a home or commercial sewing machine. Use a size 10 or 12 needle. | |
Size 33 | Lightweight polyester thread used for bobbins, and sewing garments, flags, banners, patio furniture, and lightweight sails and tents. Tensile strength is 3 pounds. Expect 12,200 Yards per pound. Inconspicuous stitching. Use with either a home or commercial sewing machine. Use a size 12 or 14 needle. | |
Size 46 | Lightweight polyester thread used for sewing garments, flags, banners, patio furniture, and sails and tents. Tensile strength is 7 pounds. Expect 9,500 Yards per pound. Inconspicuous stitching. Use with either a home or commercial sewing machine. Use a size 14 or 16 needle. | |
Size 69 | Light-middleweight polyester thread used for sewing awnings , banners, flags, patio furniture, sails and tents. Tensile strength is 11 pounds. Expect 6,000 Yards per pound. Noticeable stitching. Use with either a home or commercial sewing machine. This is the heaviest size that most home sewing machines can use. Use a size 16 or 18 needle. | |
Size 92 | Middleweight polyester thread used for sewing awnings, boat covers, auto interiors, banners, flags, patio furniture, sails and tents. Tensile strength is 15 pounds. Expect 4,500 Yards per pound. Noticeable stitching. Normally requires a commercial sewing machine. Use a size 18 or 20 needle. | |
Size 138 | Heavy middleweight polyester thread used for sewing awnings, boat covers, pool covers, auto interiors, banners, flags, patio furniture, sails and tents. Tensile strength is 21 pounds. Expect 3,000 Yards per pound. Noticeable stitching. Requires a commercial sewing machine. Use a size 20 or 22 needle. | |
Size 207 | Heavyweight polyester thread used for sewing awnings, upholstery, boat covers, pool covers, auto interiors, sails, and tents. Tensile strength is 31 pounds. Expect 2,100 Yards per pound. Stitching highly visible. Requires a commercial sewing machine. Use a size 22 or 24 needle. | |
Size 277 | Heavyweight polyester thread used for sewing awnings, upholstery, canvas, boat covers, pool covers, auto interiors, sails, and tents. Also, re-enforcing fabric and belts. Tensile strength is 44 pounds. Expect 1,500 Yards per pound. Stitching stands out. Requires a commercial sewing machine. Use a size 24 or 26 needle. | |
Size 346 | Heavyweight polyester thread used for sewing awnings, upholstery, canvas, shoe leather, boat covers, pool covers, auto interiors, sails, and tents. Also, re-enforcing fabric and belts. Tensile strength is 53 pounds. Expect 1,300 Yards per pound. Stitching stands out. Requires a commercial sewing machine. Use a size 24 or 26 needle. | |
Size 415 | Ultra heavyweight polyester thread used for sewing awnings, canvas, heavy-duty upholstery, shoe leather, auto interiors, large sails, outdoor carpeting, and large tents. Also, re-enforcing fabric and belts. Tensile strength is 73 pounds. Expect 1,000 Yards per pound. Stitching highly visible. Requires a heavy duty commercial sewing machine. Use a size 26 or 28 needle. | |
Size 554 | Ultra heavyweight polyester thread used for sewing awnings, canvas, boot leather, large sails, outdoor carpeting, and large tents. Also, re-enforcing fabric and belts. Tensile strength is 98 pounds. Expect 630 Yards per pound. Stitching highly visible. Requires a heavy duty commercial sewing machine. Use a size 28 or 30 needle. | |
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Polyester Thread Terms - Our product pages use technical terms to describe our thread. Here is a description of these terms and how they should affect your buying decisions. |
| Bonded | When thread passes through a sewing machine needle the friction creates heat and may cause the thread to fray. A bonded thread has a coating that reduces friction. Bonding is helpful if you are doing high speed sewing with thread size 46 and higher. It does not matter if you are doing hand sewing. |
| Soft | A soft thread does not have a coating that reduces sewing machine friction. This is desirable if you are using thread with glue (e.g. fly-tying) because bonding interferes with some adhesives. |
| Monocord | Most of our thread is made by twisting two or more plies to achieve the desired size. A monocord thread has a single ply that is extruded to the desired size. Monocord thread has a smooth, shiny look and feel that is similar to monofilament fishing line. The smoothness reduces friction just like bonding does |
| Non-wicking | This thread has a finish that resists liquids flowing through seams. There is a trade-off--some non-wicking finishes weaken abrasion resistance. You can minimize this problem by only using this thread when you sew high tension seams. |
| Right Twist | Sewing machines designed for the U.S. assume that thread has a left twist. If you use a right twist thread in these machines it will unravel. Right twist thread is just fine for hand sewing, reinforcing, or any project that does not require machine sewing. Also, there are some dual-head machines that require right twist thread. |
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Mil Spec Polyester Thread--Some of our nylon thread is identified as Mil Spec. This means that the thread is made in the U.S. and that the manufacturer provides paperwork (called CERTS) that certifies that it conforms to MIL-DTL-32072 (formerly VT-285F). This certification is required when thread is used on government contracts. We stock Mil Spec polyester thread in military colors such as Olive Drab, Coyote, and Shade 1600 and can special order it in almost any color and size. Special orders have a four to six week lead time, a 23 pound minimum order, and a $2.00 a pound up-charge.
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Provide CERTS retroactively for thread that does not have the manufacturers paperwork or has not been identified as Mil Spec on our site.
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Give CERTS for regular two and four ounce "Juniors" that we wind in-house because we cannot identify these spools to a batch/lot. On request, we can do a special order wind where we identify the Juniors to a manufacturer's batch/lot and issue CERTS. There is a $2.00 a spool up-charge for this service.
Manufacturers have quality control programs to test their thread before it ships. In most cases regular thread is the same as Mil Spec thread. It just does not have the CERTS. Our American & Efird, Eddington, Service Thread, and Coats products are made in the U.S. Linhanyl thread is made in Brazil.
There are many other types of certifications for nylon thread that we do not support. For example, none of our thread is certified for parachutes or medical use and we do not offer certifications for aviation and automobile manufacturers. |
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Polyester Thread Specifications |
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Sizes |
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Commercial |
15 |
33 |
46 |
69 |
92 |
138 |
207 |
277 |
346 |
415 |
554 |
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Tex |
16 |
30 |
40 |
70 |
90 |
135 |
210 |
270 |
350 |
410 |
600 |
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Government |
00 |
AA |
B |
E |
F |
FF |
3-Cord |
4-Cord |
5-Cord |
6-Cord |
8-Cord |
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U.S. |
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Tensile Strength (Pounds) |
1.5 |
3 |
7 |
11 |
15 |
21 |
31 |
44 |
53 |
73 |
98 |
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Yards-Per-Pound |
30,000 |
12,200 |
9,500 |
6,000 |
4,000 |
3.000 |
2.100 |
1.500 |
1.300 |
1.000 |
630 |
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Diameter (Inches) |
0.0047 |
0.0070 |
0.0080 |
0.0107 |
0.0124 |
0.0152 |
0.0186 |
0.0231 |
0.0258 |
0.0283 |
0.0330 |
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Metric |
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Tensile Strength (Kilograms) |
0.7 |
1.4 |
3.1 |
5.0 |
6.8 |
9.5 |
14.0 |
20.0 |
24.1 |
33.2 |
44.5 |
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Diameter (Millimeters) |
0.1194 |
0.1778 |
0.2032 |
0.2718 |
0.3150 |
0.3861 |
0.4724 |
0.5867 |
0.6553 |
0.7188 |
0.8382 |
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