Ensure that the receiver mounting block does not rest
on top of the helmet shell edge beading.
6. Position the left (as worn) jaw receiver assem-
bly and the left receiver mounting block as
shown in Figure 4-62 so that the left bayonet is
correctly positioned and the left receiver mount-
ing block fits the contour of the helmet.
Ensure that the top hole of the jaw assembly is at
least 5/8 from the edge of the helmet.
Ensure that the thicker side of the tapered receiver
mounting block is positioned toward the helmet shell
7. Adjust the left oxygen mask straps snugly.
Figure 4-62. Positioning
Oxygen Mask and
Marking Receiver Hole
You may have to adjust the oxygen mask straps several times to
achieve the optimum settings.
8. Mark the location of the top receiver hole as shown in Figure 4-62.
9. Remove mask from helmet and the bayonet from the receiver. Have the opera-
tor/wearer remove the helmet.
10. Detach the earcup from the retaining pad, and pull the earcup out of the way to
prevent damage while drilling the shell.
11. Center punch the hole marked in step 8.
Wear safety goggles (Item 10, Appendix E) when drilling the helmet shell.
Before drilling the helmet shell, ensure proper location of receivers.
This is important because the receivers are only slightly adjustable
once they are attached to the helmet.
When drilling the helmet shell, hold the drill perpendicular to the shell
to prevent damage to the shell.
12. 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 8. Use a small rattail file
to remove any rough edges.
13. Insert the inner 6-32 x 7/16 pan-head screw with external lockwasher through
the inner hole of the left bayonet receiver backing plate.
14. Insert screw, lockwasher, and backing plate from inside of helmet shell through
hole drilled in step 12.