Zen and the Art of Lockwashers

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Tom Wilson
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Zen and the Art of Lockwashers

Post by Tom Wilson »

While fixing my drivers window, I decided to clean and lube the rest of the door parts. In doing so, I encountered three different types of lockwashers; spring, inside tooth and outside tooth (and split and tab lockwashers elsewhere). It occurred to me that I have no idea when one was supposed to use one kind vrs the other and why five different kinds were even necessary. For that matter, I didn't know if the Factory installed these or if they were the product of earlier work.

I consulted the Bibles of obscure information, Carol Smiths "Nuts, Bolts, Fasteners and Plumbing" and Forbes Avid's "High Performance Hardware" and found that lockwashers are worthless and shouldn't ever be used. Their arguements sounded reasonable to me, but I am more interested in originality here and less in strength.

Anybody got a rule of thumb as to what should be used when?
Tom Wilson - Series III 250 GTE, SN 4247 GT
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fest
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lock it

Post by fest »

until just recently, i was a Manufacturing Engineer
and worked on specifiying Lock Washers for our porducts:

we specified External Tooth Lockwashers
on all applications where it was practical
i.e. there was room for one
e.g, under a PHP (Pan Head Philips)
typically Sheet Metal Stampings, etc.

we did NOT use Internal Tooth Lockwashers
as they are not as effective as External
(I will spare the details)

For applications such as SHCS (Socket Head Cap Screw)
we would specify Split Lockwashers
for example, Machined Parts
that needed to be Tightened / Loosened
for adjustment purposes

for applications that were Machined
but did not need to be adjusted
Typically FHP (Flat Head Philips)
we specifed Locktite (# 222)
and NO Lockwasher

as for Lockwashers under Nuts
we did not specify these
as they are too easily lost
(into expensive high-voltatge equipment, for example)
so we always speced out Nyloc Nuts

My brother in law the Pilot (ex Engineer)
states that the best lock nuts are the 'crimped' type

I like Nyloc, myself
and plan to sneak them into my reso job
where I am able
AKB
~~~~~~~
400i SI 32635
John Vardanian
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Post by John Vardanian »

Tom W,

I have taken a Jag 120 apart for restoration and it seems outside toothed washers were used everywhere around the body and sometimes in the engine.

Ferrari, however, like to use wave washers almost everwhere.

I personally prefer the toothed washers for electrical terminals, as they provide superior coductivity.

john
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Keith Milne
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Post by Keith Milne »

Where does the "wavey" washer fit into all of this?

Keith
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David Booth
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Post by David Booth »

Ferrari's application for the wave washers was under the nut on an aluminum part, since a regular split lock washer would gall the aluminum casting when the fastener was loosened. Therefore, almost all the nuts that are on studs used on the engine external parts, the transmission case and the rear axle will get a wave washer.
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Tom Wilson
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Post by Tom Wilson »

Thanks Fest, sounds like I found the right guy to answer this question!

In Carroll Smith's "Nuts, Bolts Fasteners and Plumbing Handbook", he says that split (spring) and wave washers do nothing because when torque is applied to the bolt, it flattens the lock washer, creating essentially a flat washer. He thought that small star washers (external teeth or serraded) give some resistance when used on soft metals, but not enough to bother with. I think his primary concern is that the lock washers give a false sense of security, which cause the user to not tighten the bolt enough, which negates any help the washer can give. He prefers loctite or safety wires.

It sounds, though, that you regularly used lock washer in your work, and so must feel that they work. Any comments on Mr. Smith?
Tom Wilson - Series III 250 GTE, SN 4247 GT
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fest
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don't rightly know

Post by fest »

I would have to agree with mr smith:
that Safety Wire is the best
(just look under the cowl of an Aircraft sometime)
I was considering using some on my car
e.g. Bolts securing Oil Pump cover inside Pump Housing
but never got around to doing it till it was too late-
Eastwood has a cool looking jiggy to drill the holes with
maybe McMaster has pre-drilled ones?

as for Loctite:
it seems to work pretty good-
but I have experienced inconsistent results
this may be due to variences in techinque
e.g. operator applying too little, surfaces not cleaned properly, etc
(Loctite just came out with a 'stick' applied product, BTW)

I have seen my share of split Lock Washers that were mashed flat-
that certainly does cast doubt on their effectiveness
the 'not tight' enough theory makes sense as well-
as I stated, we used split Lock Washers only on fasteners
that needed to be adjusted periodically (and not all that tight)
in this application,
they seem to do a good job of keeping the fasteners from loosening

we used the 'star' washers to secure PCBs a lot
and in this instance, again they worked quite well
as PCBs are easily damaged by overtorqued fasteners

we also used 'wave' or 'bellville' Washers
but these primarily were used to ensure good contact
i.e. electrical continuity (good ground)
or to ensure constant tension
(as opposed to providing a locking effect)

what did the esteemed mr smith say about
the use of lock nuts?
yea?
nay?
nada?
AKB
~~~~~~~
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Jimmyr
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Post by Jimmyr »

As a rule of thumb, wave washers were used where the nut or bolt tightens agains an alloy (alu) part, and a split lock was used against steel parts. There are some exceptions, such as the suspension assemblies where a castle nut and cotter key is used or a nylok nut is used. Nyloks are not used on heat producing assemblies due to the low melting point of nylon. On fuel lines the best sealing is from new copper washers. Fiber washers work on some damaged surfaces, but they can continue to compress over age and sometimes soften due to fuel additives, and leak. Jim Riff
Koll
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Post by Koll »

I tend to agree with Smith. I do not view washers in terms of a locking mechanism, but rather a way to spread the load out. (protection of load surface). I'm a big fan of flanged head cap screws and flanged nuts.

I use them when they're OEM. Sometimes they're there for clearance and alignment purposes (front-of-engine stuff).

I also look closely at metal reaction. I love yellow zinc (Porsche & Toyota use it a lot) with aluminum. Never stainless on AL.

I agree with Smith, if you're ever down to where the locking mechanism is what's holding the assembly together, your're screwed.

Inner star for electrical connections - they bite the metal for added conductivity. That and dielectric grease - always. Microscopic oxidation does effect electrical connections - so minimalize it when possible.
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