IBM Selectric - Page 97

2.
3.
This small clearance insu.res that the backspace pawl
will be allowed to bottom in its rack and that a mini-
mum amount of tab lever mati on wi II be requi red to re-
move both the backspace and escapement pawls from
their racks during a tabulation operation.
Tab Lever Pawl - Adjust the pawl forward or back on
the tab lever so that the tip of the pawl clears a SET
tab stop by .035" to .045" with the j"ab lever at rest
(Fig. 240).
Adjust Tab Lever
Pawl
FIGURE
240. Tab Lever Pawl
The adjustment of the tab lever pawl has an effect on
the amount of overlap between the tob stop and the
pawl tip in the active position. It also directly affects
the pawl cleorance during tabulation. Unless the tab
lever pawl is properly adjusted, correct pawl clearance
cannot be obtained.
The adjustment of the tab lever pawl can be measured
by using the push-end of the large spring hook. The
push-end is approximate Iy .035" thi c:k.
Tab Rack -
Adjust the tab rack left or right for a clear-
ance of .005" to .020 II between the tip of the tab lever
pawl and a set tab stop with the tab lever latched out.
This adjustment is made by the tab rack bushi ng on the
RH end of the tab rack. The clearance may be observed
by holdinR the carrier and latching the tab lever out
(Fig. 241).
Tab Rack Plate
.020"
Tab Powl
FIGURE 241. Tab Rack Bushing
NOTE! The head of the tab rack bushi ng should clear
the tab rack plate by about 3/32" when the adjustment
is complete.
The tab rack adjustment sets up a condition whereby the
escapement pawl wi II be released into the escapement
rack at the right time to safely engage the correct tooth.
If the tab rack were too far to the I eft, the tab lever
2-79
4.
5.
would contact the set tab stop sooner and release the es--
capement pawl into the rack earlier than it should. The
pawl
could enter the wrong escapement rack tooth and
stop the carri er one space to the I eft of the desi red stop--
ping point. The carrier could stop one space too far to
the right if the tab rack were adjusted too far to the
right.
Pawl Clearance - The upright lug of the tab latch should
be formed forward or back so that the tip of the escape-
ment pawl clears the escapement rack teeth by .005
11
to
.010" when the tab lever is latched to the rear.
Small Screwdriver
Escapement Bracket
FIGURE 242. Pawl Clearance Adjustment
The adjustment insures that the escapement pawl wi I f
re-enter the rack quickly to minimize the chances of
entering the wrong rack tooth. If excessive clearance
is present, it is a Iso possible that the tab keylever and
associated parts might not have enough throw to posi-
tive Iy latch the tab lever each time.
The upright lug of the tab latch may be formed with the
3" screwdriver by using it.as a lever through the hole in
the escapement bracket (Fig. 242). If excessive forming
is
required, recheck and refine the adjustment of the tab
lever pawl.
Adjusting Plate, 11 Inch Machine (Fig. 242.1) - Position
as follows:
a. Front to Rear - so that the actuator link and clevis
clears the power frame.
NOTE: Clearance must be observed throughout
fu" motion of the tab bel/crank.
b. With the tab interposer released and the backspac:e
cam on its
high point, rotate the torque bar (re la-
tive to the adjusting plate) so that the tab lever
overthrows the tab latch by .005" to .010". Check
to make sure the tab lever overthrow stop or the tab
torque bar overthrow stud do not limit this adjust-
ment.