NASA Fastener Design Manual

[alangbaker]

I thought this might be interesting and/or useful to folks like me:

Summary

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 .

https://ntrs.nasa.gov/api/citations/...9900009424.pdf

[Rick Kirchner]

Thanks for that.

for years I've used various Mil-specs but many are no longer updated. This is a good reference that puts everything in one place.

MIL-STD-454 and Mil HDBK-454 are two other good references

[Rick Iverson]

Carroll Smith on steroids.

[BeerBudgetRacing]

if you run it through Acrobat (or other) PDF 'size reduction' process it's half the size and no visible loss.

[Richard Hybels]

Lock washers
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

[DaveW]

Lock washers
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

What it does is to provide a bit of resistance to the nut rotating completely off once it becomes slightly loose. That's similar in function to the Nylon in a Nyloc nut.

IMO, the only thing that will prevent loosening is to pre-tension sufficiently so that the nut, screw, etc. never loses all of the clamping force between what it's clamping.

If you look closely at a nut's contact surface after use with a lock washer, you will usually see when you remove a less than grade 8 nut that the washer has "machined" off a bit of the nut while you loosened it. The washer will likely do similar damage to the opposite surface in contact with the washer.