13
BOBBIN THREAD TENSION (CONT.)
Remove the bobbin case from its holder and turn set screw in spring
in a clockwise direction to apply more tension or counterclockwise
to release tension.
When the bobbin thread tension is correct, it rarely becomes nec-
essary to make any changes as varying the needle thread tension
will usually attain a good stitch.
NEEDLE THREAD TENSION
The needle thread tension is varied by turning the tension regulating
nut (G, Fig. 3). Turning the nut in a clockwise direction increases the
tension, while counterclockwise decreases it. This should not be
done when the presser foot is in its raised position, but is generally
done while the machine is sewing on a piece of scrap material.
CHANGING THE STITCH LENGTH
Unless otherwise specified machine Styles 63900AM, AML and AT will
be equipped with upper feed regulator gear No. 63949-39 and
lower feed regulator gear No. 63949-41 to produce 9 stitches per
inch (S.P.I.), while Styles 63900AW, and AAE will be equipped with
upper feed regulator gear No. 63949-37 and lower feed regulator
gear No. 63949-43 to produce 10 S.P.I. Other gears are available and may be ordered separately. Refer
to "Gear Chart" below for the gears necessary to produce S.P.I. other than previously described.
GEAR CHART
S.P.I.
UPPER GEAR
LOWER GEAR
6
63949-47
63949-33
7
63949-44
63949-36
8
63949-41
63949-39
9
63949-39
63949-41
10
63949-37
63949-43
11
63949-36
63949-44
12
63949-33
63949-47
To remove feed regulators gears, first remove feed drive gear cover located under arm of machine. Now
loosen screws (A and B Fig. 11) and slide gears (C and D) off their respective shafts. Replace with gears for
desired stitch length. After new gears have been installed be sure to reset needle feed stitch length to
agree with the continuous turning roller feed.
