Class 99 & 99K
To Regulate Bobbin Thread Tension
The tension on the bobbin thread is regulated by the screw A, Fig. 30 which is nearest the center of the tension spring on the outside of the bobbin case. To increase the tension, turn screw A over to the right. To decrease the tension, turn this screw to the left.
When the tension on the bobbin thread has been once properly adjusted, it is seldom necessary to change it. A correct stitch can usually be obtained by varying the tension on the needle thread.
Fig. 30 Bobbin Thread Tension
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