Kenmore 1206 - Manual (Page 14)

When stitching is unsatisfactory as in figures
2 and 3, adjust the upper thread tension.
Lower thread tension requires adjustment
less frequently than the upper thread
tension.
When stitch is satisfactory, as in Fipre I and
seam is badly puckered, the cause may be
tight tensions and both upper and lower
may be adjusted. (See page 26)
When adjusting the tension on the bobbin
case, make slight adjustments with a screw­
driver. (See page 26)
INCREASE TENSION