Wear safety goggles (Item 10 Appendix E) when
drilling the helmet shell.
Figure 4-64. Measuring Distance
Place the helmet on a flat surface.
Referring to Figure 4-64, measure the
distance of the holes from the bottom of
the helmet shell.
Measure the horizontal position of the holes
from the edge beading.
Measure the same distance on the opposite
side of the helmet shell and mark a corre-
sponding location for the mounting holes for
the other receiver.
Detach the earcup from the retaining pad, and pull the earcup out of the way to
prevent damage during drilling.
Center punch holes marked in step 28.
Wear safety goggles (Item 10 Appendix E) when drilling the helmet shell.
Before drilling, ensure proper location of receivers. This is important
because the receivers are only slightly adjustable once they are at-
tached to the helmet.
When drilling, hold the drill perpendicular to the helmet shell to pre-
31. Place helmet on table. Using an electric drill (Item 9, Appendix B) and a #27 drill
bit (Item 7, Appendix B), drill the hole marked in step 28. Use a small rattail file
to remove any rough edges.
32. Using the mounting screw removed in step 25, reattach the boom and micro-
phone to the helmet.
33. Install two 6-32 x 7/16 pan-head screws, two #6 lockwashers, a bayonet
receiver backplate, a left receiver mounting block, and a jaw assembly on each
side of the helmet.
Start all four screws before tightening them.
Be sure to tighten all four screws.
34. Install earcups, have the operator/wearer don the helmet, and check earcup fit.
35. Position the mask over the operator/wearers face. Insert the left bayonet into
the left receiver two clicks and the right bayonet into the right receiver two
clicks. Adjust the oxygen mask straps for a secure seal. Attach microphone
36. Check operation of oxygen mask in accordance with TM 55-1660-247-12.