MIL-DTL-15291G
3.4.2 Insulation.
3.4.2.1 Plastic laminates. Plastic laminates when used, shall be selected to enable the switch to meet
performance requirements of this specification. For additional information and guidance on plastic
laminates see 6.11.
3.4.2.2 Plastic molding. Plastic molding material shall be selected to enable the switch to meet
performance requirements of this specification. Color shall be gray, approximating color chip Number
26307 of FED-STD-595. Molded parts shall be free of flash. For additional information and guidance on
plastic molding see 6.12.
3.4.2.3 Fungus-resistance. Insulation material shall be non-fungus nutrient.
3.4.2.4 Flammable material. Insulation material shall be fire retardant.
3.5 Design and construction. Switches shall be of closed construction so that the switching
mechanism and the switching contacts are fully enclosed (except terminals and unused terminal
locations), to prevent foreign matter from entering the switch mechanism or interfering with the contacts.
Switches shall be constructed to ensure proper operation when mounted in any position. The switches
shall be of the design, construction, class, and physical dimensions specified (see 3.1) and the switch
circuit configuration shall conform to the applicable switching characteristics specified (see 3.1 and 6.2).
3.5.1 Assembled switches. Parts of the assembled switch shall work freely and the switch shall be
positive in action.
3.5.2 Relation of parts. In assembling the switch, the relationship between the handle shaft assembly
and the switch blades shall be as specified in 3.1 so that the shaft or handle positions will agree with the
mounting of switches in electrical switchboards and equipment.
3.5.3 Contact mating. The moving switch blade contacts shall mate with both sides of the stationary
contacts at the contact engagement areas with uniform positive pressure.
accordance with FED-STD-H28. Wherever possible, unified screw threads shall be used. Where a
special diameter-pitch combination is required, the thread shall be of American National Form and of any
pitch which is used in the fine-thread series.
3.5.4.1 Engagement of threaded parts. Threaded parts shall engage at least three full threads in soft
metals like aluminum and its alloys. Not less than two full threads shall be used in harder materials such
as brass or steel. When a screw mates with a plastic part, a threaded metal insert shall be molded
therein.
3.5.5 Locking of screw-thread assemblies. Unless otherwise specified (see 3.1), except for terminal
hardware screw-thread assemblies shall be rendered resistant to loosening under vibration. Unless
otherwise specified (see 3.1), bronze, stainless steel or plated steel split type, or internal-tooth
lockwashers shall be provided under nuts or screw heads. The use of locknuts is permitted in lieu of
lockwashers.
terminal hardware is not assembled to the switch, it shall be placed in a bag and firmly secured to the
switch.
3.5.7 Moving contact material. Moving contact material shall be selected to enable the switch to meet
performance requirements of this specification. For additional information and guidance on moving
contact material see 6.13.
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