Singer 271K - Driving Lever Spring Tension

KNIFE BAR STOP
/^ll
CONNECTlNGnTAP LIGHTLY
LINK ^init^r^UPON DRIVING
./>-—LEVER
A SLIGHT ^
CLEARANCE
STARTING^'^^
LEVER IN nl.
"RUN" POSITION
CONNECTING
STUD
APPROX. 1/64"
CLEARANCE
I
KNIFE BAR
UP
KNIFE
Fig. 37. Knife Bar at Correct Height
REACH KNIFE
BAR CLAMPING
SCREW THRU
THIS HOLE
Fig. 38. Ad|usting Knife Bar Height
LOOSEN
TO ADJUST ^11 O'CLOCK
r-.>;^POSITION
DRIVING
LEVER
AUTOMATIC
KNIFE DISENGAGING
LEVER IN CONTROL
KNIFE BAR
SPRING ARM
Fig. 39. Adjust Knife Bar Spring Tension
KNIFE BAR HEIGHT
When knife bar is at correct height, as shown
in Fig. 37, there will be only a slight clearance
(o small amount of play) between knife bar con*
necting stud and top of slot inside knife bar
connecting link. This setting is necessary to
insure approximately
1/64 inch clearance (in
side knife bar stop) between top of knife bar
and inside-top of knife bar stop, so that knife
bar will not rap against knife bar stop on its
return stroke, after cutting buttonhole. During
adjustment, starting lever must be at "run"
position (knife bar up), as shown in Fig. 37.
Loosen knife bar clamping screw, as instructed
in Fig. 38.
With knife bar in its highest posi
tion, press down on forward end of driving lever,
Fig. 37, forcing connecting stud at rear end of
driving lever to bear against top end of
slot in
connecting link. Tighten clamping screw just
enough to hold knife bar in position. Tap lightly
upon REAR END of driving lever, as instructed
in Fig. 37, until there is a slight clearance
between stud and link. Then securely tighten
knife bar clamping screw.
DRIVING LEVER SPRING TENSION
Tension on the knife bar driving lever spring,
shown in Fig. 39, should be just sufficient to
hold knife bar at its highest position, whenever
thread breakage occurs and automatic knife
disengaging lever goes into operation.
Excessive tension on this spring may cause
knife bar to break knife bar stop on its return
stroke.
To adjust, loosen hex-head screw, shown in
Fig. 39. Set spring arm at 11 o'clock position.
Tighten hex-head screw. Hook spring arm under
driving lever, as shown.
17
From the library of: Superior Sewing Machine & Supply LLC