[TR] difference between these two washers

[Dave MacKay]

>Date: Fri, 3 Feb 2023 09:31:17 -0800

>From: Sujit Roy <triumphstag at gmail.com>

>To: Triumphs <triumphs at autox.team.net>

>Subject: [TR] difference between these two washers

>

>Besides, looks, what are the differences between these washers? Why use
one compared to the other? I typically see the left one used for lighter
loads, but never under a load which needs torquing up.

>Sujit

>

>Sujit Roy

>Cupertino, California

>URL: <
http://autox.team.net/pipermail/triumphs/attachments/20230203/1f2337ba/attachment-0001.jpg
>



On pp 116-117 of Carroll Shelby’s *Nuts, Bolts, Fasteners and Plumbing
Handbook*, Shelby discusses the lock washers including star washers (like
the one on the left of the image) and spring lock washers (like the one on
the right of the image).



“Lock washers



There are a great many locking devices on the market today. The most
popular is also the least effective --- the lock washer. There are three
basic types of lock washers: the spring washer, the wave washer and the
serrated, or star, washer.



Nether the spring washer nor the wave washer do anything worth talking
about --- other than to provide the user with a false sense of security.
Think about it for a moment. From experience, you know that it takes very
little load to compress a spring washer. For example, the spring washer
will be completely closed long before we reach recommended torque when
tightening a bolt. Once compressed, the spring washer is nothing but a flat
washer. If, for whatever reason, a bolt should loosen to the point where
the spring washer opens enough to become a spring, there was too little
residual stress in the assembled bolt for any sort of safety. In other
words, the thing wasn’t tightened sufficiently. Exactly the same is true of
the wave washer which is, for some reason or other, popular in Germany. If
you decide to use a spring lock washer, a flat washer should be placed
between the lock washer and the work surface to prevent damage to the
surface. This in not necessary with the wave washer.



I am willing to admit that there are installations where the serrated or
star washer can be effective . These installations are limited to the
smaller sizes and almost always have to do with machine screws bearing on a
rather soft surface --- aluminum or plastic, for example. The teeth of the
washer can and do bite into the surfaces of soft materials and offer
reasonably positive protection against rotation. They are available with
either internal or external teeth, and also as coned washers for
countersunk bolts.



I try not to use lock washers. I use prevailing torque-type self-locking
nuts on all through holes and check or jam nuts to lock rod end bearings
and threaded adjusters. With blind holes, if I do not trust the thread
portion of a properly tightened bolt, I use the appropriate grade of
Loctite and/or safety wire. I do, however, carry a selection of aircraft
spec (AN-935) spring lock washers [similar to the one on the right of the
image] around with me --- just in case. I will not use industrial [rather
than aircraft-grade] spring lock washers because they are liable to be too
brittle for my taste.”



Dave MacKay

1960 TR3A (s/n 68639L)

Near Toronto, Canada
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