TM 9-1240-285-34&P
BACKLASH CHECK (CONT)
5-2.
FRAME 1
Procedure
Step
Install telescope mount (1) into vise, such that there is free access to both the elevation and
1.
inflection knob assemblies.
2.
Install telescope (2) into telescope mount (1) (TM 20-2).
NOTE
The following steps are to be done for both deflec-
tion and elevation boresight knob backlash
checks.
3.
Sight a target through telescope (2) that is in the midpoint of travel for boresight knob (3).
NOTE
In the following steps make sure that the directions
for rotating the boresight knobs (3) in a specified
direction are followed. If boresight knobs (3) are
turned back and forth to sight target the check will
be inaccurate.
4.
Rotate boresight knob (3) counterclockwise to lowest reading on boresight scale (4). Then
rotate boresight knob (3) clockwise only and center target in telescopes reticle. Record read-
ing on bore sight scale (4).
5.
Rotate bore sight knob (3) clockwise to highest reading on boresight scale (4). Then rotate
boresight knob (3) counterclockwise only and center target in telescope's reticle. Record
reading on boresight scale (4).
Boresight elevation and deflection backlash should not exceed 0.1 mils.
6.
The deflection boresight knob shall provide a minimum of 20 roils movement in each
direction when the deflection dial scale is in the 3 position. The elevation boresight
knob shall provide a minimum of 40 roils movement in elevation when the elevation
dial scale is in the 1 position.
Torque requirements for rotation of the boresight knobs through full excursion shall
not exceed 8 in.-lb.
If criteria in lines 6, 7, and 8 is not met, replace special screw (para 4-10 for elevation
knob and para 4-13 for deflection knob).
END OF TASK
I
Para 5-2 Cont
5-2
Change 1
Vol II
