SINGER W231 - Manual (Page 11)

Correct Stitch
Needle Thread Tension too strong
Needle Thread Tension too weak
Fig. 18
the *7lpiead
For ordinary stitching the tension of the upper and lower
threads should be equal so as to lock both threads in the
center of the material (Fig. 18). If one tension is stronger
than the other, imperfect stitching will result. Fine
materials require a light tension, while heavy materials
require more tension to obtain a perfect stitch.
TO INCREASE the tension, turn the thread tension dial
(Fig. 17) clockwise.
TO LE)SSEN the tension, turn the thread tension dial in
the opposite direction. (When regulating the tension
always have the presser foot down).
As all machines are correctly adjusted
before leaving the factory and read­
justed before the dealer delivers them
to you, the lower tension seldom re­
quires to be altered, but, if this
becomes necessary, tighten the screw
in the tension spring on the outside of
the bobbin case for more tension, or
loosen the screw slightly for lesser
tension (Fig. 16).
\
fig. U
Fig. 17