Yes, you can use 40 weight thread in the bobbin, especially for quilting or general sewing where you want durability and a visible stitch, but you'll likely need to adjust your machine's tension and might get better results with thinner bobbin thread (like 60wt or 80wt) for less bulk, especially in embroidery. Using a finer bobbin thread allows the top thread to dominate, creating flatter seams and preventing buildup, while 40wt on the bottom provides strength but adds bulk.
Medium Weight Threads
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.
Bobbin thread is a lighter weight thread, often around 60 – 80 wt used in the bobbin of your sewing machine. It is designed to be strong but fine enough to prevent adding bulk to your seams.
There is no rule that states you must use the same thread in the bobbin as you do on top. It is perfectly fine to use a different thread in the bobbin than what is used on top. It is also perfectly fine to use a thinner thread in the bobbin than what is used on top (different weights, such as a 40 wt.
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.
70/10 – 100 weight threads. 80/12 – 50 weight threads. 90/14 – 40 weight threads. 100/16 – 30 weight threads and thicker.
Bottom Line is a 60 wt./2-ply polyester thread that has been designed to be used as a bobbin thread. It's fine diameter helps it to blend well and its filament construction makes it extremely smooth, so it glides through fabric when stitched.
Many machine quilters like using a filament poly thread in the bobbin. Due to it's slick surface, it works well with metallic threads and heavy cotton threads. The slickness of the filament poly thread does not snag or grab the top thread.
A 30-wt. thread is a “heavier” thread, meaning a thicker cross section, because a much shorter thread weighs the same as the 40 wt. In length measurements, higher numbers reflect thicker or heavier threads.
Tension Problems
Both the upper thread tension and bobbin tension can affect how your machine stitches. If the tension is too tight or too loose, it can lead to uneven stitching and bunching of the bobbin thread. - Adjust the upper thread tension using the dial on your sewing machine, starting with a medium setting.
Unlike regular threads and other bobbin fills, Janome Bobbin Fill is a 90 weight polyester thread.
You can use whatever color you want, but you don't need to change color to match the top thread. Your bobbin thread should not show through the top layer of stitching. It will only be seen on the back of the item. The reason you want to use a lightweight thread is to avoid too much bulk on the back of the item.
For intricate designs, a lighter thread like a 90 weight bobbin thread is ideal, as it reduces bulk and allows for more precise stitching. On the other hand, heavier threads are better suited for general sewing and projects that require more durability.
If you like Gutermann (and I definitely do!), look out for their Coton 30 machine quilting threads, which are completely safe to use in your sewing machine.
60 Weight Thread Offers Digitizers Unique Opportunity
Madeira Classic #60 is approximately 60% finer than Classic Rayon #40. It comes on 1500 meter spools and boasts the same color fastness (to 95 degree washing temperature) as Classic Rayon #40.
When the bobbin thread is not correctly wound onto the bobbin or threaded through the bobbin case, it can lead to uneven tension and thread bunching underneath the fabric. This can cause the sewing machine to jam as the tangled threads interfere with the needle's movement.
Experts say a sewing machine can last 5 to 25 years. This depends on where it's used and how it's taken care of. Taking good care of it and keeping it in check can make it last longer.
When you ask, “why is my thread looping underneath?”, it's often because the upper thread is on closed tension discs. This happens when the presser foot is down while threading. The thread then has no tension, leading to loops underneath. This is a common issue, more noticeable on lightweight fabrics or shiny threads.
When using the sewing side of the machine, you can use regular all-purpose thread in the bobbin, but when using the embroidery side, you will need to use what is called "bobbinfil". This is a finer weight thread that is ideal for embroidery.
40wt is thicker & shows up a bit more so it just depends on whether you want that or not. Also, if you switch to 40wt thread, be sure to also switch your needle size accordingly. Pretty much all manufacturers tell you the recommended needle size for each weight.
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.
Weight refers to a thread's thickness. In the world of embroidery and cotton thread, a lower thread weight number is thicker than a higher thread weight. This means that a 40 Weight thread is thinner than a 30 Weight thread.
Medium Weight Threads
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.