MIL-DTL-24646B
3.5.2 Threaded parts and fastening devices. Threaded parts and fastening devices shall be as specified in
MIL-E-917 with the exceptions specified in 3.5.2.1 and 3.5.2.2.
3.5.2.1 Screw threads. Screw threads shall be as specified in FED-STD-28. Unless otherwise specified (see 3.1),
screw threads shall be right-hand, coarse-thread series, unified form, class 2A or 2B as specified in FED-STD-28/2.
3.5.2.2 Thread locking at electrical connections. Thread locking at electrical connections shall be as follows:
a.
Lockwashers need not be used to lock the nuts at the main bus nor the nuts at the fuse clips, providing
b.
Unless otherwise furnished with the switch, lockwashers need not be used with the screw at the switch
terminal.
3.5.3 Welding and brazing. Welding and brazing of nonelectrical parts shall be in accordance with commercial
practices and shall meet the requirements specified herein.
3.5.3.1 Brazing. Parts or components shall be fastened by intermittent localized brazing in such a manner as to
ensure that each enclosure assembly will not be completely soft-annealed and will not distort or leak when subjected
to the shock tests (see 4.6.9).
3.5.4 Stress relief. Metals used in the fuse box assemblies shall be treated or heat treated to prevent deterioration
or failure due to stresses or other conditions resulting from working, forming, and similar processes during fabrication.
3.5.5 Drilling, countersinking, and tapping. Drilling, countersinking, and tapping shall be done before painting or
finish is applied.
3.5.6 Sealing counterbored holes. Counterbored holes in the bottom of the fuse base shall be filled with type I,
grade D rosin or sealing wax as specified in A-A-59142 after screws are in place.
3.5.7 Component spacing and arrangement. Unless otherwise specified (see 3.1), component spacing and
arrangement within the boxes shall be as follows:
a.
Current carrying parts shall be so arranged as to avoid overheating due to inductive effects.
b.
Terminals shall be offset to facilitate wiring. In a box having three main terminals, the holes in the two outer
terminals shall be angled in towards the center terminal between 15 degrees and 30 degrees. In a box
having two main terminals, the holes in each shall be angled in towards the other between 15 degrees and
30 degrees. The holes in the branch terminals shall be offset approximately 30 degrees in the same
direction as specified in Drawing 9000-S6202-73055.
c.
Fuse clips shall be aligned so as not to apply stresses to fuses.
3.5.8 Electrical creepage and clearance distances. Unless an insulating barrier is used, electrical creepage and
clearance distances shall be as specified in MIL-E-917.
3.5.8.1 Insulating barriers. Insulating barriers shall be of the same materials as the base and shall be a minimum
of .125 inch (3.17 mm) thick when there is a possibility of impact or abrasion to the material resulting from shock or
vibration, otherwise it can be .062 inch (1.57 mm) thick. Barriers for branch buses shall be force-fit and cemented in
a slot cut into the base. The cement shall be commercial grade and shall be such as to prevent the barriers from
becoming loosened during the shock and vibration tests (see 4.6.9 and 4.6.8). Barriers (sub bases) for main buses
shall be secured by through bolting with the same studs holding the main buses.
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