SINGER 10 - Manual (Page 19)

5, 6, 8, 10 Stitch Sewing Machines
Adjusting thread tension
When an even amount of tension is exerted on both
threads, a smooth even stitch, known as a balanced
stitch, is produced.
Correct tension is important because too much or too
little will weaken your seams or cause your fabric to
pucker. Make a test sample with the fabric and thread
you plan to use and examine it.
A perfect, well balanced stitch (1), will have the needle
and bobbin threads locked between the two layers of
fabric with no loops on top or bottom and no
puckering.
Too much tension will produce a tight stitch (2) which
will cause the fabric to pucker.
* To decrease tension, turn the dial to a lower number.
Too little tension will produce a loose stitch (3) which
will cause loops in your seam.
* To increase tension, turn the dial to a higher
number.
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