Bobbin Thread
The thinner thread loaded in a small spool beneath the needle plate, which locks the top thread on the back of the fabric.
Bobbin thread is the secondary thread that locks the top thread on the underside of the fabric. It is wound onto a small spool (the bobbin) that sits in the bobbin case beneath the needle plate. Each stitch is formed when the top thread loops through the fabric, the rotary hook catches it, and the bobbin thread interlocks with it before the needle pulls up.
Bobbin thread is generally finer than top thread, typically 60-weight to 75-weight polyester or cotton, and almost always white or black. Black bobbin is used on dark garments, white on light. The customer never sees the bobbin thread on the finished design front, but it is fully visible on the back of the embroidery.
Pre-wound bobbins (cardboard-sided or magnetic-sided plastic) are the industry standard, sold in cases of a hundred or more. They save the time and labor of winding bobbins on the machine. A typical pre-wound bobbin holds enough thread for thousands of stitches. Operators change bobbins frequently during high-volume production.
A poorly tensioned bobbin is one of the most common sources of embroidery defects. If the bobbin tension is too tight, the top thread pulls down and disappears into the fabric. If too loose, the top thread loops and snags on the surface. Operators check and adjust bobbin tension on every machine at the start of every shift.
Related Terms
- Top Thread →
- The decorative embroidery thread loaded on the top of the machine, which is the thread the customer sees in the finished design.
- Polyester Embroidery Thread →
- The most common type of embroidery top thread, valued for its strength, colorfastness, and resistance to bleach and abrasion.
- Trim Command →
- An instruction embedded in the stitch file that tells the machine to cut the top and bobbin threads before moving to the next stitch section.
- Stitch Density →
- The spacing between stitches in a design, controlling thread coverage, stiffness, and total stitch count.
- Pull Compensation →
- An adjustment a digitizer applies that widens shapes in the stitch file so they hold their intended size after the fabric pulls in from the stitching.