Explain washer use to me!

[TomB]

Please can someone explain the use of washers to me.

Why do some fasteners require them, and other do not? For example, in building up the front suspension, specifically the lower wishbone, the 2000 era build manual say to use a spring washer and a plain washer under the front bolt head. But the rear bolt doesn’t use washers at all under the nut or the bolt head. The upper wishbones do not appear have have any washers. I can’t make sense why some seemingly similar fasteners don’t require them but others do. 

Should a spring, lock or shakeproof washer always be used with a plain washer. 

Why don’t wheel nuts or rod end nuts have them?

 

[Wrightpayne]

Where there is a nyloc nut you dont need a spring / star washer - they do the same thing ie stop it coming undone.

Plain washer / no plain washer - good question! Await good reply!!

Ian

[elie boone]

A plain washer is used to spread the load on the mounting surface when it's considered to thin or could flex to much. 

[Paul Mason]

After many years of nagging I now understand how to work the cotton, wool and normal cycles, where to put the detergent and the fabric conditioner. All relatively easy to be honest. Boom boom! (Well someone was always going to stay something daft on this topic, so may as well be me in-keeping with my character)

[virden]

 I agree with Elie's explanation for use of plain washers and I was taught to use spring washers where the bolt was subject to excessive vibration or high temperatures which would melt nylocs.

[elie boone]

Normally one doesn't use a washer under a Nylock nut, for the reason that if the washer would turn due to vibration it can un tighten the Nylock nut. And the spring washer of mine preference is Schnorr but the black one, there is also a zinc plated one but IMHO any treatment on a spring washer can compromise it's characteristics. 

[TomB]

Thanks for your thoughts.  However, I see some disparities between the build manual and suggestions above.  On the rear suspension, there are plain and spring washers on some of the de-dion ear to de-dion tube fasteners.  The spring washer is there to stop the bolt coming undone, but what is the plain washer for?  Does a spring need fitting with a plain irrespective of whether the mounting surface could flex?

I read on the web somewhere that a plain washer can be use to prevent damage to the mounting surface, or it developing wear from repeated use.  Taken the front suspension again, use of a plain washer under the nut would prevent abrasion of the steel/powder coat on the chassis bracket, rathert than having the turning nyloc directly on the bracket.    

[SLR No.77]

What about wave washers? The intake trumpets on my roller barrels are retained using a dozen M5 cap screws each with a small wave washer ... what is the function of the washer?

Stu.

[TomB]

I've dug my 2000 era manual out.  In the introductory sections it says:

The majority of fasteners have washers inserted between the nut and or bolt head and the item being secured.  Spring washers or lock washers are usually placed next to the bolt head or nut then the plain washer.  As a general rule the following washers are used as follows:

• Plain washer: to protect the surface and spread a load when attaching to soft material such as aluminum or fibre glass; to adjust the spacing of one component to another; to present a uniform surface on which to tighten a fastening onto a rough or irregular surface. 
• Spring washer: to lock a thread where there is possibility of a nut or bolt working loose. Not used with a nyloc nut.
• Large diameter thin plain washer: to spread a load on a thin surface.
• Large diameter plain washer: to prevent migration (sideways movement) of rubber bushes.
• The large 1/2" plain chamfered washers are often used with suspension bushes. The chamfered edge must be fitted towards the bush to prevent contact with the metal part of the bush.  

OK so much of that makes sense.  My car being 1996, is between the 200 era and 1988 era manuals.  Taking a single fastening, the lower wishbone rear, as its common between the two manuals, the 1988 manual, says to put a plain washer under the bolt head, but not under the nut.  The 2000 manual doesn't have any washers under the nut or bolt head.  

What is the logic for having a washer under the head but not the nut ?  Both ends of the fastening have a similar bracket on the chassis.  

 

 

 

[CharlesElliott]

Generally, when a plain washer is used under a spring washer it is to prevent damage to the surface. 

[Grubbster]

I don't think I'd expect to find 100% compliance with 'washer-use logic' when reading the Caterham assembly guide, when I built both of mine the application of washers seemed quite random!

[Wrightpayne]

Oops - I built mine wrong then “chamfered edge towards the bush”

I wonder if this explains the oft complained about diff noise on the forum?

Ian

[Jonathan Kay]

• The large 1/2" plain chamfered washers are often used with suspension bushes. The chamfered edge must be fitted towards the bush to prevent contact with the metal part of the bush.  

That one has come up a few times. A pictorial or verbal explanation would be an asset to the knowledgebase.

Jonathan

PS: John Vine's notes on the correct placing of Schnorr washers for the BMW diff. 

[Jonathan Kay]

 

• Spring washer: to lock a thread where there is possibility of a nut or bolt working loose. Not used with a nyloc nut.

NASA Fastener Design Manual 1990. That's the one casting doubt on whether split ring washers work.

...

Wikipedia on washers. Includes that debate and a brief comment on the effectiveness of wave washers.

Jonathan

[Jonathan Kay]

After many years of nagging I now understand how to work the cotton, wool and normal cycles, where to put the detergent and the fabric conditioner.

:-)

Not particularly interesting machines, except for:

1. Illustrating how not to design human-machine interfaces.
2. The sheer ugliness of using concrete blocks to keep the drum under control. (What would ACBC have done?)
3. The wonderful Keymatic control system.

Jonathan

[Wile7]

"A plain washer is used to spread the load on the mounting surface when it's considered to thin or could flex to much...."

Exactly that......   

[Sim]

The sheer ugliness of using concrete blocks to keep the drum under control. (What would ACBC have done?)

Maybe that's why you're a doctor and not an engineer JK!

This is a case where 'just add lightness' doesn't apply.

Instead its more of ' An Engineer can do for a dollar what any fool can do for two' ( attributed to Arthur Wellington - US railway engineer) 

 

Simon

[7 wonders of the world]

Best thing you can do with wave, star and spring washer is weigh them in for scrap...... their effectiveness as a means of retention is very poor, the later are known to break and fall out leaving the fastener loose.

Schnorr washer are possible the best locking washer,

If heat is a problem for nyloc then consider Philidas (Aerolock) nuts,

for cap screws retaining fittings around the intake - look to drill and lock wire them as a belt and braces approach.

[SLR No.77]

Yep I found it a costly mistake to rely on the Caterham/Titan supplied wave washers to actually do anything, in reality they have absolutely to useful function other than being a reasonably lightweight alternative to something thicker. Lockwire definitely the way to go,

Stu.

[Bricol]

Nordlock washers for locking washers - work well on machinery that vibrates.

Just don't do what I have seen done - use a plain washer under the nordlock washer, totally negating the effectiveness of the norklock . . .