Polyester Thread Use and Size Guide

Please visit our website for more information on this topic.

Why Polyester? - Polyester thread looks, feels, and sews like nylon. You cannot tell the difference just by looking at it just by looking, and technical specifications like strength and stretch are similar. This means that polyester works just as nylon in most applications including: upholstery, leatherwork, auto interiors, banners and flags, sports gear, dog collars, horse saddles and tack, knife sheaths, gun holsters, fishing lures, and brief cases. So, why use polyester? Polyester does better than nylon when you are sewing things that have prolonged exposure to sunlight, mildew, bleaching, acids, and alkalis. The keyword here is prolonged. Let's say you were sewing a tent; if you plan to leave the tent in the backyard all summer for your children then you should use polyester. If you use the tent for weekend camping trips, then nylon or polyester would work just as well.

Here are examples of things that should be sewn with polyester:

Pool Covers

Tarpaulins

Outdoor Furniture

Banners

Flags

Polyester thread does not provide the ultimate sunlight (UV) resistance. Brands like Sunbrella and Tenara come with replacement guarantees and UV treated nylon and polyester threads will out perform regular polyester. None of this matters if the material sewn is not equally bleach and sunlight resistant. After all, the material makes up at least 90% of the content and cost of the item that is being sewn.

There are times when polyester thread should not be used:

Fire retardant garments and gear - Polyester thread sticks at 440F and melts at 483F. This is too low for any application where thread and material must withstand high temperatures. Use Kevlar, Nomex, and PTFE Fiberglass threads in these situations. Kevlar and Nomex are heat resistant to 700F and do not melt; PTFE fiberglass protects to 1,000F. Critical need for strength - Polyester thread is strong enough for the kinds of applications described so far. But, it is a bad choice for high stress applications such as conveyer belts because it can stretch up to 25% before it breaks. Size-for-size Kevlar Thread is about twice as strong as polyester and nylon. For example, Size 92 polyester has a 14.5 pound tensile strength; Kevlar in that size has a 30 pound tensile strength. Also, Kevlar only stretches 5% before it breaks.

Technically, our polyester thread is called filament polyester. It should not be confused with these other polyester threads:

Polyester Embroidery Thread - Polyester is rapidly replacing rayon as the first choice for embroidery. It is known for high sheen and standing up to washing and bleach. We have many polyester embroidery threads on our Embroidery and Sewing page and feature Robison-Anton Super Brite Polyester in about 400 colors. Spun Polyester - Most of the thread used for sewing garments are spun polyesters sold under names like Perma Core and Maxi Lock. They are strong and look an feel like cotton because they are hair thin polyester filaments wrapped in cotton. We have Robison-Anton Spun Polyester 700-yard mini spools for $1.50 and a Spun Polyester Grab Bag of partial spools for $2 a pound. Factoid - Telling The Difference - Reading the label is always the best way to tell if a thread is nylon or polyester. If there is no label, you can tell by burning the thread in a safe, well ventilated area. Nylon thread (left) burns cleanly and leaves a gray ash. Polyester thread (right) burns brighter, has a foul odor that should not be breathed, and leaves a gooey plastic-like ball. Polyester Thread Size / Thickness - Polyester thread comes in eleven sizes or thicknesses that range from hair-thin with a 1.5 pound tensile strength to 1 millimeter thick with a 98 pound strength.   Our Polyester Thread Uses / Size Ranges gives recommendations for about 30 typical polyester thread sewing applications. Polyester thread thickness affects almost everything. As thread size increases:
Thread diameter increases - Thread is spongy and thickness cannot be measured with calipers. Instead, thread sizes refer to the weight of a given length of thread. For example 1,000 meters a Size 69 / Tex 70 weighs 70 grams. Also, the tightness of a thread's twist and the bonding (coating) used affect thickness. Having said this, U.S. military specifications for polyester thread include diameters. We include this information on the Polyester Specifications chart. Thread and seam strength increase - Seam strength is misunderstood when it comes to clothing and lightweight gear. A light-middleweight thread Size 69 / Tex 70 has an 11 pound tensile strength that most people cannot break by pulling. Also, the material sewn costs much more than the thread used to sew it. In most cases (parachutes excepted) it is better for the thread to break have the material fray. Thread size matters most when it comes to covers and enclosures. In these cases seam stress increases as the area enclosed and tension caused by stretching materials over frames. This means that thread size needs it increase to handle the stress. The tents on the right illustrate this point. The camping tent would use a sizes between 46 and 92; the shelter tent would use thread in the size 207 to 554 range. Stitch visibility increases - This can be either good or bad depending on how you want your work to look. When you use a thread Size 138 / Tex 135 or higher the stitches become noticeable; at Size 277 / Tex 270 they become a focal point as shown on the right. Also, thread colors that contrast with the material and stitch size increase visibility. Finally, uniform stitching is critical because any mistakes really stand out.

Needle size increases - A thicker thread requires a larger needle. Our Needle and Thread Size Chart and the Polyester Thread Specifications give the range of needle sizes used with each thread size. We give ranges because the physical thickness of thread varies by size. Generally, it is best to use the smallest needle size that has a large enough eye for the thread. Material thickness increases - Like thread, fabric and leather thickness cannot be measured with calipers. Instead, it is measured by how much a yard of material weighs in ounces. Here is a table that shows how the range of polyester thread sizes used increases as material thickness increases. Note that leather uses thicker thread sizes because it is denser than fabric. Fabric Ounces Per Yard Thread Size Range Leather Ounces Per Yard Thread Size Range 2 to 6 Ounces 15 to 33 1 to 8 Ounces 46 to 207 6 to 8 Ounces 33 to 47 8 to 12 Ounces 138 to 277 8 to 10 Ounces 46 to 69 12 to 16 Ounces 138 to 346 10 to 12 Ounces 69 to 92 Multiple Layers 207 to 346 12 to 14 Ounces 92 to 207     Sewing machine requirements increase - Sewing machines work by punching holes in material and forcing thread through the hole to make the stitch. A thicker thread requires a larger hole and a larger hole requires a more powerful machine. Home machines (flat shank needles) usually can handle polyester thread up to Size 69 / Tex 70, commercial machines can handle thread up to Size 207 / Tex 210, and heavy duty (walking foot) machines are needed for sizes 277 / Tex 270 and up. Yards per pound decreases - Polyester thread is sold by spool weight -- not the length of thread on the spool. For example, a Size 46 / Tex 45 polyester yields about 10,000 yards per pound; Size 207 / Tex 210 yields about 2,100 yards per pound. Polyester Thread Size Descriptions - Here are brief descriptions of the eleven polyester thread sizes that we stock. See our Polyester Thread Uses / Size Ranges page for size recommendations about specific thread uses, and our  Polyester Thread Specifications page for technical details.     Size 15 / Tex 16 / Govt. 00 Ultra thin thread that is mainly used for light sewing and to embroider leather and fabric.

Size 33 / Tex 35 / Govt. AA

Lightweight thread that is used for sewing garments and very thin leather such as purses and wallets.

Size 46 / Tex 45 / Govt. B

Lightweight thread used for sewing lightweight outdoor gear (e.g. tents), thin leather, and light outdoor garments.

Size 69 / Tex 70 / Govt. E

Most popular size, best color selection. Great for lightweight and middleweight sewing. Use for outdoor furniture, leather, gear, garments, upholstery, drapes. Largest size for most home sewing machines.

Size 92 / Tex 90 / Govt. F

Middleweight thread that is used for tents, furniture upholstery, auto upholstery, dog beds and collars, sails, and sand bags.

Size 138 / Tex 135 / Govt. FF

Middleweight thread that is sometimes used for heavier weight sewing because stitches are noticeable. Typical uses include auto upholstery and convertible tops, awnings, party tents, pool covers, tarpaulins, and sails.

Size 207 / Tex 210 / Govt. 3-Cord

Heavyweight thread. Typical uses include auto upholstery, furniture upholstery, boat covers, awnings, tarpaulins, and saddles and horse tack.

Size 277 / Tex 277 / Govt. 4-Cord

Heavyweight thread used for hand and machine sewing. Typical uses include horse saddles and tack, knife sheaths, holsters, tarpaulins, banners, boat and pool covers. Its stitches are a focal point.

Size 346 / Tex 350 / Govt. 5-Cord

Heavyweight thread used for hand and machine sewing. Typical uses include canvas tarpaulins, saddles, horse tack, shoe repair, conveyer belts, holsters, and sheaths. Its stitches are a focal point.

Size 415 / Tex 410 / Govt. 6-Cord

Heavyweight thread used for hand and machine sewing. It is also a survival pack staple. Typical uses include canvas tarpaulins, saddles, horse tack, shoe repair, conveyor belts, holsters, and sheaths. Its stitches are a focal point.

Size 554 / Tex 600 / Govt. 8-Cord

Our heaviest thread with a 1 mm diameter. It is used for very heavy duty hand and machine sewing and for tying, binding, and hanging. Stitches are a focal point. How to Buy Polyester Thread - Here are six things you should know when buying polyester thread:

• Putups - Putup refers to the amount of thread on a spool. Commercial sewers generally by polyester thread by the pound; hobbyists and casual sewers can save with our two and four ounce spools.
• Color - Polyester thread comes in many colors. Our color images work well in most cases. But, thread samples may be needed for precise matches.
• Bonded or Soft? - Most polyester thread has a coating (or bonding) for smoother sewing and less fraying.
• Monocord -

   Regular polyester thread has two or more plies that are twisted together and bonded. Monocord polyester thread is made from hair-thin filaments that are bonded together in a single ply.

• Elongation - The amount of stretch in the thread
• Twist - Most polyester has two or more plies that are twisted to the left or right. This affects the types of machines that can use the thread.

Putups - Most of our polyester thread comes in 16, 4, and 2 ounce spools (or putups) as shown on the left. Our commercial customers usually prefer 16 ounce spools for high volume sewing jobs because they cost less per ounce and reduce time lost changing spools. Casual sewers often save by buying the smaller 2 and 4 ounce spools because they avoid paying for thread they will never use. The smaller putups also work well when businesses need to have a variety of colors for repairs.

We stock some of our polyester thread in case quantities at a 10 to 20% discount. Please call if you need a color that we do not stock in case quantities. We will be glad to special order it and give a 10% discount. Lead time is 4 to 6 weeks.

Industry norms allow polyester thread spool weights to vary by plus/minus 10% from the stated nominal weight. This means that you might slightly more or slightly less thread on any spool and use the term "nominal" weight in our descriptions. Here is a table that shows our nominal sizes and the weight ranges for each side including the weight of the spool itself. When a spool falls within these ranges we do not charge for overages or refund underages.

  Nominal Weight Nominal Minimum Nominal Maximum Nominal Weight Nominal Minimum Nominal Maximum

2 Oz

2.6 Oz

4.5 Oz

8 Oz

8.0 Oz

10.5 Oz

4 Oz

4.6 Oz

5.9 Oz

12 Oz

10.6 Oz

15.5 Oz

sft contains other products and information you need, so please check it out.

6 Oz

6.0 Oz

7.9 Oz

16 Oz

15.6 Oz

19.9 Oz

Polyester thread comes on spools that vary with the putup size:

• 2 and 4 ounce putups come on spools that are 2.5 inches at the base and 4.0 inches high.
• 16 ounce putups mostly come on spools that are 4.5 inches at be base and 7.5 inches high.

Some home sewing machines do not have spindles that can handle these polyester spools. We have Thread Cone Holders (right) that solve this problem by feeding thread into your machine.

  Color - We have polyester thread in over 100 colors. To help with color selection, we divide our color pallet into these colors - black, white, beige, blue, brown, gray, green, orange, purple, red and yellow. Then, we sequence shades from light to dark to make color comparisons easier.

When we add a color, the thread is photographed under controlled lighting conditions. Then, we eliminate highlights and shadows by selecting a small swatch.  Finally, we visually compare the swatch to the spool and make corrections if needed.

This process results in highly accurate color representation on our site. Unfortunately, some things are beyond our control. For example:

• Colors shown on your monitor change appearance depending on the surrounding lighting and your viewing angle.
• Your monitor color settings affect the thread looks on your screen.
• Bonded thread on the spool looks slightly darker than it looks when sewn into fabric or leather.
• Thread and fabric manufacturers have minor run-to-run color variations.

Please call us at 800-915- when you need a precise color match. We can help by sending a reasonable number of samples, or by having you send the fabric or leather and matching it here.

Bonded or Soft? - A bonded thread has a coating that reduces needle heat and fraying; a soft thread does not have this coating. Bonding only matters if you are using the thread for machine sewing. It makes no difference if you are hand sewing or using the thread to hang or reinforce things.

Bonding does little to help lightweight threads in sizes 46 or lower and soft threads work just as well. It is the norm for threads size 69 and higher. This is why almost all of our threads are bonded.

Monocord - Regular polyester thread is made by twisting two or more plies together and bonding them. Monocord is made from hair-thin polyester filaments that are extruded together in a single ply. Up close, monocord thread is smooth, flat, and ribbon-like. Some say it looks like monofilament fishing line. Here are monocord's advantages and disadvantages: Advantages:

• 10 to 14% stronger than twisted thread
• Runs smoother, fewer needle changes
• Works with both needles on a dual needle machine.
• Excels at bi-directional sewing
• Excels at low profile applications where stitches are buried in the material.

Disadvantages:

• Machines need to be re-tensioned when switching between twisted and monocord thread.

Bottom line, we do not recommend monocord thread for inexperienced, casual or low volume sewers because of re-tensioning. Monocord has significant advantages for commercial sewing such as upholstery, auto interiors, outdoor gear, and pet accessories. Elongation - This refers to a thread's stretchiness. Polyester thread has a 26% elongation factor. If you had a 100 foot length of polyester and pulled on it until it snaps, it would be 126 foot long at that point.

Polyester thread's stretchiness is a good thing because It lets seams stretch as fabric or leather stretches. The alternative is seam puckering or the thread snapping. If you are sewing material that does not stretch (e.g. vinyl or cardboard), polyester's 26% elongation factor usually does not matter because material's inelasticity does not stress the thread.

If you are using polyester thread to hang, reinforce or bind, you should consider its elongation. Less stretchy such as  Kevlar, waxed thread, and cord and string are usually better choices.

Twist - Sewing machines designed for the U.S. market use left twist ( also called Z-twist) thread. Almost all of our thread is left twist and the few exceptions are clearly identified as "Right Twist".

Be aware of these situations:

• Double needle usually require right twist thread in the left needle.
• Monocord thread does not have a twist and can be used on either side of a double needle machine.
• Polyester thread's twist does not matter when you are using it for hand sewing, hanging, binding, or hanging.

Polyester Thread Specifications

Here are U.S. military specifications (MIL-DTL- / VT-285F) for polyester thread. Please note:

• Polyester thread sizes are based on the ratio of a fixed length of thread to its weight - not its diameter. This is because thread is spongy and its diameter cannot be measured with calipers. Bonding increases a thread's thickness.
• Bonding also reduces the number of yards-per-pound for a given size.
• Average Break Strength is for twisted thread. Monocord threads are 10% to 14% stronger
• Metric data is calculated using standard conversion factors. Small rounding differences are inevitable.
• Needle size ranges come from other sources and are not part of the mil-spec.

Lightweight and Middleweight - Sizes 15 to 138

Size

Tex

16 35 45 70 90 135

Military

A AA B E F FF Average Break Strength            

Pounds

1.5 3.0 7.0 11.0 14.5 21.0

Metric

0.7 1.4 3.2 5.0 6.6 9.5 Diameter            

Thousandths of Inch

. . . . . .

Millimeters

0. 0. 0. 0. 0. 0. Average Per Pound            

Yards

30,000 12,200 9,500 6,000 4,500 3,000

Meters

27,272 11,090 8,636 5,454 4,091 2,727 Needle Size Range            

U.S.

10-12 12-14 14-16 16-18 18-20 20-22

Metric

70-80 80-90 90-100 100-110 110-120 120-140

Heavyweight - Sizes 207 to 554

Size  

Tex

210 270 350 410 600  

Military

3-Cord / 18 4-Cord 5-Cord 6-Cord 8-Cord   Average Break Strength            

Pounds

31.0 44.0 53.0 73.0 98.0  

Metric

14.1 22.0 24.1 37.7 44.5   Diameter            

Thousandths of Inch

0. 0. 0. 0. 0.  

Millimeters

0. 0. 0. 0. 0.   Average Per Pound            

Yards

2,100 1,500 1,300 1,000 630  

Meters

955 682 591 455 286   Needle Size Range            

U.S.

22-24 24-26 26-28 28-30 30-32  

Metric

140-180 180-220 220-260 260-300 300-360   Polyester Thread Usage and Size Guide

Here are 19 sewing applications that typically use polyester thread and the range of thread sizes that can be used with each. There is no right size for any application because four things have to be balanced: material thickness and density; seam strength requirements; stitch visibility preferences; and sewing machine capabilities. Often, the "right" thread size is a compromise that balances these competing needs.

This reduced-sheen monofilament polyester is the best choice when it comes to invisible threads. Unlike other monofilament threads made from nylon, MonoPoly is 100% polyester. Commonly referred to as an invisible thread due to its fineness and reduced-sheen, MonoPoly is great for the bobbin or top. Available in two colors, Smoke (for dark fabrics) and Clear (for light fabrics).

Want more information on Polyester Monofilament Yarn? Feel free to contact us.