IBM Selectric - Page 34

7.
PrintCamFollowerStopScrew - Adjust the cam follower
stop screw
so that the print cam follower roller clears
the print cam by .020" when the machine is at rest
(Fig. 81). This clearance allows the roller to shift from
one lobe to the other without rubbing on the cam. Use
the
following procedure to obtain this adjustment:
FIGURE 81. Print Cam Follower Stop Screw
a. With the machine resting on its back, slowly hand
cycle a high velocity character until the leading
edge of the print shaft keyway I ines up with the
center of the roller pin on the cam follower (Fig. 82).
I~ __ - - - - - - __ -L::j
I ------- I
~i ~
~~.'I I ",.t III!I!I!!!III!I~
==~!I I~I ~
LJ I;
~ Pin 1
3
I I "I
I I I I
l
'-, I I
, I--r-
-" I I i--
I
Keyway
I I I
I I I I
l __ -_-.= = = ~J
FIGURE 82. Keyway In Line With Roller
b. loosen the stop screw locking nut and back out the
stop screw approximately two turns. (The roller
should be resting against the cam at this point.)
c. Withthemachinerestingon its back, place a .001"
or .002" feeter gauge between the print cam and
the follower roller (Fig. 83). This can be accom-
plished by manually holding the rocker toward the
platen while inserting the feeler gauge from the
front of the carrier{to the right of the carrier pointer)
just
above the line lock bracket. With the gauge
32
in position I allow the rocker to come back to rest.
The feeler gauge should become trapped between the
roller and the cam. Then I slowly turn the stop screw
in until a minimum
drag is felt on the feeler gauge as
it
is withdrawn.
FIGURE 83. Feeler Gauge Trapped
d. Tighten the locking nut without moving the screw.
NOTE: Thisadjustment may be checked by apply-
ing a light film of #17 grease on the print cam (in
the area indicated in Fig. 84) and then observing the
track that the roller makes in the grease when the
machine is hand-cycled. If the stop screw has been
adjusted properly, the roller track in the grease
should
begin at point "A" (Fig. 84) which is the
beginning of the second low dwell on the print cam.
If the rollertrack begins before point II A", the roller
isadjusted too close to the print cam when the ma-
chine is at rest. Improper roller to cam clearance
may cause the roller to drag on the print cam as it
shifts during a low velocity selection. Thus, the
roller may fail to shift, or shift improperly. If the
roller is adjusted too close to the cam at rest I it
may receive a ski -jump effect from the print cam as
it attempts to follow the print cam from the first
low dwell to the second low dwell. This will create
excessive noise and wear along "4/ith an adverse
effect on the type head impact velocity.
If the roller track begins after point II A" , the roller
rests too far away from the first low dwell of the
print cam and a loss in typehead velocity may result.
FIGURE 84. Roller Track In Grease