This manual was written for design engineers to enable them to choose appropriate fasteners for their designs. Subject matter includes fastener material selection, platings, lubricants, corrosion, locking methods, washers, inserts, thread types and classes, fatigue loading, and fastener torque. A section on design criteria covers the derivation of torque formulas, loads on a fastener group, combining simultaneous shear and tension loads, pullout load for tapped holes, grip length, head styles, and fastener strengths. The second half of this manual presents general guidelines and selection criteria for rivets and lockbolts.

NASA ( National Aeronautics and Space Administration), for aerospace products, NASA has developed its own standards, its standards not only include aircraft design, but also cover the most basic fastener design selection. Among them, the standard for fasteners is NASA Perference Publication 1228 Fastener Design Manual.

The main components of NASA fastener design standards include Fastener Materials , Platings and Coatings,Thread Lubricants, Corrosion, Locking Methods, Washers, Inserts, Threads, Fatigue-Resistant Bolts, Fastener Torque, Design Criteria, below is a screenshot of the full text of which can be downloaded above.

In particular, the NASA Fastener Design Manual has specific instructions for open spring washers, as follows:

Fastener Design Manual PDF Download for Free,Helical Spring Washer is Useless for Locking

Fastener Design Manual PDF Download for Free,Helical Spring Washer is Useless for Locking

The typical helical spring washer shown in figure 14 is made of slightly trapezoidal wire formed into a helix of one coil so that the free height is approximately twice the thickness of the washer cross section. They are usually made of hardened carbon steel, but they are also available in aluminum, silicon,brome,phosphor-bronze, stainless steel, and K-Monel.

The lockwasher serves as a spring while the bolt is being tightened. However, the washer is normally flat by the time the bolt is fully torqued. At this time it is equivalent to a solid flat washer, and its locking ability is nonexistent. In summary, a Iockwasher of this type is useless for locking.

Fastener Design Manual PDF Download:https://ntrs.nasa.gov/api/citations/19900009424/downloads/19900009424.pdf

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