FUNDAMENTALS OF CLOTHING CONSTRUCTION 3(1+2)

Lesson 3 : Sewing Machine

Testing the tension of threads

Both the upper thread and the bobbin thread are to be at a slight tension for the formation of a perfect stitch. When both tensions are appropriate, a perfect stitch is formed with the threads interlocking in the middle of the two fabrics thicknesses which is shown below (fig a).

This seam will be strong and can with stand stress and strain.

If the top thread is too tight then it lies straight on the top side of the fabric with loops of under thread on it. If the bobbin thread tension is greater then the bobbin thread will lie in a straight line on the underside of fabric, showing loops of the upper thread on it.

An easy method of testing the tensions of both top thread and bobbin thread is to stitch along the diagonal (Two layer) of a square piece of cloth and pulling it apart. The thread that breaks is the one with tight tension.

A basic rule is to adjust the top thread tension and bottom thread tension is seldom done.