Superior Education



Which thread is best for sewing on leather?

Bonded nylon thread is a superb choice of thread to sew leather, and it comes in a variety of weights that pair well with different weights and thicknesses of leather. Bonded nylon is a strong thread, and the bonding process it undergoes adds strength and reduces friction, making sewing smoother and faster on an industrial sewing machine. It is perfect for hand sewing leather because the bonding agent (a type of resin) helps dissipate friction during the sewing process. It's strength keeps the thread from unraveling as it's drawn through the layers of leather and other thick materials.

Matching thread to the leather is important. When sewing leather on a sewing machine, the stitches need to be short enough to provide a tight seam, but not so short that the leather is weakened by too many perforations. Bonded nylon will keep tight seams and will look attractive, especially when sewn in decorative stitch patterns.

To make a smooth, continuous stitch along the seam of a piece of leather, the initial knot that is formed by the top thread and the bobbin thread are best to be hidden inside the layers of leather. Also known as buying your thread or knot. This helps provide a clean and polished look to the stitch line. Soft leather, such as that for a wallet, bag, or purse can be sewn using #46 or #69 bonded nylon thread. These two thicknesses are on the lighter weight scale and are typically used when stitches are meant to be close together or decorative in nature.

Sewing on leather

For leather material that is a little thicker and more stiff, perhaps in the 3 – 5 oz. range, a thicker thread, such as bonded nylon #92 is recommended. If the sewn leather will bear a load or be used for furniture, then a #138 thread could be considered. Size #138 thread also makes for a decorative reinforcing thread when used to accent the seam.

While some leather workers and craftsmen use size #92 on leather that is as heavy as 6 - 8 oz., it is really up to personal preference. The higher the number for bonded nylon, the thicker the thread will be. This means that you will need to use a larger needle to accommodate this thick thread. There is also a correlation between the thickness of bonded nylon and its breaking strength. Similar to diameter, the higher the number, the stronger the thread will be.

When sewing on heavy leather, such as 12 oz. or thicker, we suggest sewing with #207 or #277. When sewing with thick thread such as these two sizes, the stitch length should be lengthened to help create even spacing. It's quite unfortunate if the stitches aren't even, as it could cause too much tension on the leather material itself lead to degradation and tearing. Sewing leather that is 3/8” to 3/4” thick will be better paired with our thickest bonded thread, size #346. This heavy duty thread is extremely strong and holds its stitch well.

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