MIL-R-19309D
3.3.8.1 Thread projection. Screws or bolts secured by nuts or other retaining devices shall be of such length that a minimum of 1.5 threads and a maximum of .125 inch plus 1.5 threads for screws up to one inch in length and .25 inch plus 1.5 threads for screws over one inch in length, shall project beyond the retainer. These requirements shall not
be construed to preclude the use of screws assembled in blind holes or spacers, or where design restrictions require that the threaded portion of the screw be flush with the retaining device. In no case shall the screw be clipped, bent,
or otherwise shortened after plating.
3.3.8.2 Thread engagement. Screws and bolts in tapped parts other than nuts shall enter and engage for a distance at least equal to the diameter of the screw or bolt.
3.3.8.3 Setscrews. Where setscrews are used, they shall be in accordance with the requirements of Type G or H
of FF-S-86.
3.3.8.4 Self-tapping screws. Self-tapping screws will not be acceptable except where employed in approved components and where their removal from the component is a remote possibility.
3.3.8.5 Locking devices. Locking devices shall be provided for all screw-thread assemblies except for captive screws on withdrawable units. The working loose of threaded parts during tests or in service will be considered a defect in design. All lockwashers shall conform to the standards of Section 3 of OSTD 600 or applicable Military Standards and shall be fabricated of corrosion-resistant steel, plated phosphor-bronze, or steel zinc-plated in accordance with ASTM 8633, Type II, Class 2 or 3.
3.3.8.5.1 Exclusion. External-tooth lockwashers shall not be used with screws .25 inch or greater in diameter.
3.3.8.5.2 Spring-type lockwashers. Spring-type lockwashers may be used for screws of all sizes.
3.3.9 Methods of wiring.
3.3.9.1 Termination. No more than three wires, including wires from parts, shall terminate at any one terminal.
3.3.9.2 Pressure contacts. Electrical connections shall not depend upon wires, lugs, or terminals clamped between a metallic and an insulating or pliable material. Connections of this type shall be clamped between rigid metallic members, such as in an assembly of a machine screw, two nuts, and two washers. If such an assembly cannot be used and maintenance of a tight connection depends upon the resistance of an insulating or pliable material to compressive stress or shear, the connection shall be securely soldered.
3.4 Construction and design.
3.4.1 General.
3.4.1.1 Objective. The basic design objectives are that the equipment will meet the needs of the Naval service and that the final product will reflect the utmost in simplicity, have maximum reliability consistent with the state of the art,
be easy to operate and maintain, and be economical to produce.
3.4.1.2 Needs of the Naval service. The equipment shall be designed to withstand storage and service conditions over long periods.
3.4.1.3 Reliability. It is imperative that reliability of operation be considered of prime importance.
3.4.1.4 Simplicity. The equipment shall represent the simplest design consistent with the operational and environmental conditions set forth in this specification.
3.4.2 Dimensions and tolerances. Dimensions and tolerances of the relay shall conform to those shown on
Drawing 1521140.
3.4.3 Weight. The weight of the relay shall not exceed three ounces.
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