SINGER W951 - Manual (Page 13)

ADJUSTING THE TENSIONS
Always adjust the upper tension with the presser foot down, as the
tension is released when it is raised. To increase the tension on the
upper thread, turn dial “A” (Fig. 18) to the right (clockwise) or to the
left (counterclockwise) to decrease the tension.
Before adjusting lower tension, be sure the machine is threaded
correctly.
When it is necessary to change the bobbin tension, turn the small screw
(Fig. 22) on the side of the bobbin case clockwise to tighten, counter
clockwise to loosen.
Fig. 18
Fig. 19 Fig. 20
When the upper and lower tensions are properly balanced, a
perfect stitch will be formed with both threads interlocking in fabric
(Fig. 19).
When the upper tension is too tight, the lower thr^d is pull«l up
over the upper thread which is lying flat on the fabric (Fig. 20).
When the uppa" tension is too loose, the upper thread forms
loops over the lower thread lying flat on the fabric (Fig. 21),
Fig. 21
Fig. 22
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