Thread Tension
Thread tension is the setting used to balance the tension applied to the upper and lower threads, or multiple threads, in a sewing machine so that stitches are formed properly.
Contents6 sections
Definition and Overview
Thread tension refers to the tension applied to the thread during sewing and the balance of that tension. On lockstitch sewing machines, it mainly adjusts the balance between the upper and lower thread tensions, aiming for the stitch intersection to sit in the middle of the fabric thickness.
Upper thread tension is usually adjusted with a thread tension device or thread tension dial. The lower thread side is determined by mechanisms such as the bobbin case, and routine adjustments are made mainly on the upper thread side.
Effects of Thread Material and Structure
Proper thread tension changes depending on the sewing thread material, thickness, twist, surface slipperiness, stretch, and so on. Even with the same setting, check the stitches when switching from polyester thread to cotton thread, or from a fine thread to a thicker thread.
Threads with a lot of fuzz, loosely twisted threads, and elastic threads require attention because resistance in the thread path and feeding behavior can change easily. When changing the needle, thread, or fabric being used, do a test sew on a scrap piece and review the settings.
Relationship with Thread Count
Thread tension is not the same as the thread count or size count that indicates thread thickness. Thread count is a standard for representing thread thickness, while thread tension is the setting for the tension applied to the thread threaded into the sewing machine. Thicker thread does not always require stronger tension.
When using threads of different thicknesses, check needle hole compatibility, smooth passage through the thread path, and the appearance of the stitches. It is important not to decide values based only on thread thickness, but to adjust them under actual sewing conditions.
Sewing Checks and Precautions
If upper thread tension is too strong, the lower thread will be pulled to the surface; if it is too weak, the upper thread will tend to be pulled to the underside. If thread stands out on one side of the stitch, the thread forms loops, or puckering occurs, check the thread tension.
However, the cause of a problem is not limited to thread tension. Also check for incorrect threading, bent or worn needles, mismatch between needle and thread, bobbin winding condition, and fabric feeding before making adjustments.
- Do test sewing with the fabric, thread, needle, and sewing speed set close to the actual production conditions.
- Do not move the dial dramatically; change it little by little and compare the stitches.
- On overlock machines and coverstitch machines, check the tension balance of each thread individually.
Differences from Similar Terms
Thread tension is a different concept from the upper thread and lower thread. Upper thread and lower thread are the thread categories that make up the stitch, while thread tension refers to the tension applied to them and the balance of that tension.
A thread tension dial is the name for the machine part or operating section that mainly adjusts upper thread tension. Also, sewability is the property of a combination of thread, fabric, needle, and sewing machine to sew smoothly, and thread tension is one of the factors that affects sewability.
Frequently Asked Questions
How do you adjust thread tension?
Do a test sew with the fabric and thread you will use, check the stitches on both sides, and adjust little by little from the upper thread side. A guideline is that the stitch intersection should be in the middle of the fabric thickness, with neither side showing the opposite thread noticeably, and with no puckering or loops.
Is looping of the upper thread on the underside caused by thread tension?
This is a phenomenon that tends to occur when upper thread tension is weak, but it is also often caused by the thread not being threaded correctly through the tension device. First raise the presser foot and rethread the upper thread, then check the needle condition, thread path, and bobbin setup before adjusting the tension.
Do you need to change the thread tension when you change the thread?
It may be necessary. When the material, thickness, twist, or surface condition changes, the resistance in the thread path and the tightness of the stitch change. Even with the same size count indication, differences can appear, so check with test sewing each time you change the thread.
