Bobbin Thread 101

If it is working properly and tension is perfect, you won’t notice your bobbin thread. Don’t let that fool you. Bobbin thread still plays an important role in successful machine embroidery.

Bobbin thread is often ignored when troubleshooting embroidery problems. Since it does not go through a needle, there are fewer problems with bobbin threads than with top threads. Still, there are several things you should know.

Bobbin Thread Styles

For home sewers and embroiderers, bobbins come in three basic types: Class 15, L-style, and M-style. The type you use depends on the machine you have. Most home machines use L-style while many longarm machines use the larger M-style.

Your owner’s manual should tell you the type of bobbin you need. If not, Superior Threads has a wonderful list of bobbin types for dozens of machine brands and models.

Bobbin Thread Types

You can wind most any thread for use in the bobbin. That is standard procedure when stitching freestanding applique or freestanding lace designs. As far as standard bobbins are concerned, there are two basic thread types: Cotton and polyester.


Quilters love it. It keeps the fiber content consistent with the fabric, batting, and top thread. For light embroidery designs, cotton bobbin thread is okay but dense fill designs get quite stiff. Always choose a good quality bobbin thread. Lower quality cottons produce more lint which, in turn, requires more frequent machine cleaning. 


This thread has a shiny appearance and is virtually lint free. It is thin and lightweight, yet very strong. Embroiderers love this thread since it creates a soft backing, even on dense designs.

Heirloom Feathers by Embroider Weekly

Many machine quilters like using a polyester thread in the bobbin. Smooth, poly thread does not snag or grab the top thread. It works well with metallic threads and heavy cotton threads. If you’ve had trouble using metallics or heavy cotton threads, a slick poly thread in the bobbin may solve some problems. 

Bobbin Thread Weights

Sewers wind 50 wt. thread on their bobbin. For machine embroidery and quilting, most bobbin threads are of the 60 wt. variety. You may even use 100 wt. when stitching delicate heirloom projects.

Bobbins: Pre-wound or Self-wound

Early on, many machine manufacturers warned against using pre-wound bobbins. Now, they are available for most makes and models and many staff educators use them.

Plastic bobbins are reusable, cardboard bobbins are disposable, and some bobbin threads are wound without holders.

Pre-wound bobbins save time, making them very convenient. If you run out in the middle of an embroidery design or a quilting or sewing project, just pop a pre-wound bobbin in the machine. Having to wind a new bobbin is always an inconvenience.

Perhaps even better, pre-wound bobbins are more economical. High-tech machines provide a smooth, uniform wind. As a result, pre-wound bobbins hold three times the amount of thread as a bobbin that you wind at home.


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Thread Colors

Brands – Embroidery designs are created in many different brands of embroidery programs like Brother, Husqvarna, Artista, Pfaff etc. When designs are converted from one format to another, the thread colors used in one format are often not compatible with the thread colors another format uses. When this happens, the colors shown in your embroidery design may look rather unusual and not like the original image of the design displayed on the website. Don’t worry, this is normal and there are many different ways you can make it look correct.

Color charts are often included with your designs – When you order designs from the Internet, you will generally receive a color chart to use with your designs which gives you a guide of the thread colors to use. You should follow this color chart, rather then the color sequence of your embroidery design file. The color chart should be included inside the zipped file downloaded with your embroidery designs. Some embroidery programs can’t read the color charts, so you have to ensure you are viewing the contents of the zipped file outside of your embroidery program. Many of the latest color charts include a list of the color names, or picture of colored squares as the guideline, instead of the brand of thread. This makes it easier for you to choose the matching color from your own thread collection.

Thread conversions – Sometimes the color charts are brand specific and refer to a particular brand of embroidery thread the designer used. You may use a different embroidery thread. If so, you will need a thread conversion chart. There is a list of different thread conversion charts available further down this page.

Use your embroidery software to work out the colors for your design – If you can’t find the color chart with your embroidery designs, don’t worry – you can easily work out what colors to use with your designs. Every embroidery program should give you the options and tools to enable you to change the colors of your design to the ones you want to use. It’s easy to change colors using Embird. This great conversion program enables you to make many changes to your designs before you sew them out. If you don’t have Embird, we highly recommend you download the free trial and give it a go.

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Balancing Tension

Getting the perfect stitch is the goal of all sewing – It is fine to use different threads in the top and the bottom, whether they be different fiber types (for example, cotton and polyester) or different thicknesses. Adjustments for these differences are made with the tension settings, usually to the top tension, but occasionally to the bobbin. Machines differ in tension settings from brand to brand. Some machines seem very eager to please and they love everything we do. Other machines require lots of attention and extra training. Most machines are somewhere in the middle. Even within brands, there is some variance from machine to machine. Just like a dog, if we learn how to train or adjust the machine, it will serve us well and bring much happiness. An untrained machine (and dog) can cause more frustration than joy!

If adjusting your top tension doesn’t work, you may need to loosen your bobbin tension – If you have experienced problems running decorative threads and have adjusted the top tension every possible way and still cannot get good results, the solution might lie in the bobbin tension setting. For example, if the top thread is breaking because the top tension is too tight, it is necessary to loosen it. If you loosen it to the point where the thread does not break, but the top thread then loops on the back, the top tension is now too loose.

This is a common problem with some longarm machines. – Neither of these solutions work and adjusting the tension settings in between these two extremes doesn’t work so what can we do? The problem is that the top tension and bottom tension are too far out of sync so no matter what we do to the top tension, it will not solve the problem. In order to fix this, we must loosen the bobbin tension. Many of us were taught to NEVER touch the bobbin tension. That was when thread choices were very limited and decorative threads hadn’t yet been invented or used on high speed and longarm machines. Times have changed.

How to change your bobbin tension – If you can thread a sewing machine, you can adjust the bobbin tension. There is no need to spend money on a second bobbin case. With a permanent marker, put a dot where the tension screw is now pointing to so you can always return to the original setting. Then, with a screwdriver and thinking of a clock, make adjustments by turning the screw equivalent to what a 10-15 minute movement would be. Counterclockwise loosens the tension (the most commonly required adjustment) and clockwise tightens the tension. Remember, “lefty loosey, righty tighty”. For longarm machines, the bobbin tension should be loose enough that if you hold the bobbin case in your left hand and pull the thread up with your right hand, the bobbin case should not lift off your left hand. The old “4 inch drop test” is gone. Now, after having loosened the bobbin tension, any adjustments you make to the top tension will be more effective because the top and bottom tensions are more in sync. You should be able to pull the thread through the needle fairly easily without feeling much tension. You have now been given permission to adjust the bobbin tension! It will make a huge difference.

Preset – Sewing machines are factory preset to have the top and bottom thread form even stitches. If the top and bottom threads are identical in fiber and weight, adjustments should not be necessary. However, if we use cotton on top and poly underneath, or metallic on top and poly underneath, or a heavy thread on top and a thin thread underneath, it is necessary to adjust the tension settings. It is fine to use different thread types and weights on the top and bottom.

Tug of War – Think of the top and bottom thread as having a tug of war. If the threads are identical and you are sewing on a single layer of fabric, both sides have equal strength and the result will be a draw. The sewing should therefore produce perfectly even stitches with no top thread showing underneath and no bobbin thread showing on top. However, in the real world, the teams are rarely equal. We use decorative threads on top. We often use different fibers for the top and bottom threads. We also add stabilizer or batting. Sometimes we might use a cotton bobbin thread and other times we use a polyester bobbin thread. All these factors make it necessary to adjust the tension for each project. By adjusting the top tension either up or down, we are able to add or take away strength on the top thread team to equalize the tug of war battle.

Considerations – Here is a list of things that affect stitch results: Batting – This adds drag on top thread. Cotton batting tends to grab the thread more than poly batting, adding more friction on the thread. Fabric type – Dense fabric puts more stress on the thread. Top thread thickness and type – Metallic is less flexible than cotton or poly. Poly is stronger than either cotton or rayon. Bobbin thread type – Cotton bobbin thread tends to grab more than a silk-like filament poly. Sometimes grabbing is preferred and sometimes it causes problems. A silk-like filament poly thread (not spun poly) in the bobbin will work better with metallic or a heavier cotton and spun poly thread because its silk-like finish acts almost like a lubricant, sliding nicely with the thread.

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Common Thread Problems

Thread breaks – Causes: incorrect needle, burrs in needle eye, hook or throat plate, machine threaded incorrectly, incorrect needle bar height, tension adjustment needed, bent needle, machine needs lubrication, lint buildup, incorrect digitizing causing design to be too dense in an area, need for a silicon spray due to friction caused by thick fabrics or fabrics with treatments, pooling of thread which causes portions of the spool to wind off improperly – use Incredible Tape to prevent this

Needle breakage – Causes: timing needs adjusting for needle and hook point, needle in machine incorrectly, bent or dull needle.

Thread pileups on back of fabric – Causes: tension adjustment needed, machine incorrectly threaded.

Stitching not following pattern outline – Causes: bent needles, loose hoop in frame.

Flat stitching – Causes: tension tightness, topping film necessary on fabrics with a pile.

Looping – Causes: tension adjustment needed for tight fabric weaves, digitized with too many stitches.

Pigtailing – Cause: Top tension too tight.

Skipped stitches – Causes: wrong bobbin timing, incorrect needle size.

Puckering – Causes: tension too tight, backing not hooped the same tension as fabric, fabric hooped too tightly, needles not sharp enough, density of design too thick and needs to be increased in size slightly.

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Thread Measurements

Weight – The most common embroidery weight thread is 40Wt and suitable for most embroidery designs. Sometimes when designs are too dense, you can try using a lighter 50wt thread. Bobbin threads are generally finer and are often 60wt. The smaller the number, the heavier the thread. The higher the number, the lighter the thread. Common thread weights are 30 wt., 40 wt., and 50 wt.

Denier. Weight (in grams) of 9000 meters of thread. A larger number indicates heavier thread. A number such as 120/2 equals two strands of 120 denier thread for a total of 240 denier. Most embroidery thread has a denier measurement. However, this measurement traditionally applies only to synthetic threads. Comparative note: a 40 wt. thread approximately equals 240 denier.

Tex – Weight (in grams) of 1000 meters of thread. 40 wt. = 240 denier = tex 25.

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