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What use is a washer

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Wolfie26/12/2011 22:14:11
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502 forum posts
I have asked loads of engineers this question and I have yet to receive a satisfactory answer.
 
What is a washer for??
 
(with the obvious exception of spreading the load of a smaller headed fastener)
Stovepipe26/12/2011 22:29:27
196 forum posts
Also avoids the metal under the bolt head being gouged if the bolt turns.
(I can see the punsters gathering on this one, so be prepared !)
 
Dennis
_Paul_26/12/2011 22:33:53
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543 forum posts
31 photos
The dishes....sorry couldnt resist
 
What type of washer? plain? there are literally thousands of types, some thrust washers for instance stop your car crankshaft hitting the block webs.
 
Regards
 
Paul
Roy Moss26/12/2011 22:47:29
11 forum posts
I was faced with this question whilst working on highly-stressed aircraft parts. If there was no purpose in using washers, there was a weight advantage in removing them. I could only suggest that washers provided a smooth suface for bolts and nuts to turn aganst, and therefore limited the tightening torque which is lost lost in friction, and also prevented surface scratches which could lead to fatigue failures.
 
Roy Moss
Jeff Dayman26/12/2011 23:32:18
2356 forum posts
47 photos
The OP's original question is rather broad in scope. Obviously some rubber washers are needed in plumbing to keep the water on the wet side!
 
For washers under screw heads or nuts they prevent stress concentration at one point or few points on rough surfaces. In wood, plastic or other soft material structures they spread the load and prevent pullout. On painted steel structures they save the paint getting chewed up.
 
Soft copper, aluminum or lead/tin alloy washers are sometimes used as seals under bolt heads for oil and coolant in cars and trucks.
 
JD
Nicholas Farr27/12/2011 00:39:47
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3988 forum posts
1799 photos
Hi Wolfie, you have said it yourself, they spread the load, and as Jeff says will prevent stress concentration and pullout, they do also aid tightening up bolts without causing undue damage to the parts that you are fixing together. This assuming you are talking about the standard flat washer, as there are many types, including star, shakeproof, sping, wavey ect. There are also what is knowen as hardend flat washers, which are very often used with high tensile bolts/nuts, and are often used in situations of extreme vibration e.g. vibrating screens, as ordenary washers will tend to creep under such conditions, thus making the fixture to become loose and the bolt to rattle in the hole, causing wearing of the hole and bolt.
 
Regards Nick.
Ady127/12/2011 04:41:35
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6137 forum posts
893 photos
with the obvious exception of spreading the load of a smaller headed fastener
 
That's the main use.
 
Either make a bolt out of a solid 20mm bar
 
Or make a bolt out of 14mm bar and add a one penny 20mm washer
 
...and multiply the money/resources saved....by one billion...per week
 
....which soon adds up to a serious chunk of change
Martin Morrison27/12/2011 08:25:41
1 forum posts
Folks,
This was a question that I commonly asked when I was serving my time as a marine engineer,the journeymen told me several answers and all seem very sensible when explained.
One reason as mentioned above was to spread the load of the bolt on the clamped surface. Another reason is that many people use an oversised drill when boring the clearance hole, in this case the raised shoulder under the bolt head was either in the hole or partially over the hole, this caused the sharp edges of the nut to bite the material, when this happens in an application with higher vibration i.e. engines, aircraft's the sharp edge will cause the metal to crack, the washer with the round edge eliminated the chance of cracking, just like a circular saw blade with several slots in it and a bored hole inward of the slot.
 
Martin.
Gordon W27/12/2011 09:52:45
2011 forum posts
We have had all this before. In an ideal design washers are not needed, a std. washer is the same dia. as the across flat measurement of the bolt head/nut, and the chamfer on the head stops digging in. Of course there are all sorts of special washers, a lot of them are not much use in practice.
Steve Garnett27/12/2011 09:54:07
837 forum posts
27 photos
Stepped washers are used a lot in electronic applications as insulators. A very common example of this is the mounting of power transistors on heatsinks, where you don't want the mounting bolt (generally at collector potential) to come into contact with the heatsink, which is generally at ground potential.
 
Also you get tabbed washers fitted on keyed shafts, which can effectively lock single bolts in place.
 
And since the original question wasn't qualified in any way, I think it's only fair to point out that you also get parts washers, which are excellent for removing grease!
Rufus Roughcut27/12/2011 10:30:50
83 forum posts
20 photos
Gents
 
It's obvious that a washer is to keep she who must be obeyed out of our dens
 
Bazz
maurice bennie27/12/2011 15:50:47
164 forum posts
1 photos
Hi there,One more use for a washer ,to stop ally being forced down the hole against the stud .preventing the cylinder head being removed ,Thats my two penny worth .
happy new year everyone . Maurice
Ian S C28/12/2011 02:58:27
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7468 forum posts
230 photos
With slotted or castelated nuts a nut on the bolt may require either no washer, or a thick or thin, or combination of washers to aline the holes. The assembly instructions will usually say that a torqued assembly shall have/ or not have a washer. Ian S C
Bazyle29/12/2011 19:33:42
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6956 forum posts
229 photos
As well as the multiply serrated washers for fairly obviously locking the screw head by digging in there are the single split washers for the same job and finally the slightly wavey washers for this purpose. I could never believe the last would work adding only a little tension in the bolt but lots of important bits in aircraft rely on it so it must be effective.
Then there are the washers used to take up and adjust end float for shafts and bearings or electric motors or on cars axles, or soft alloy ones with a fold over tab to lock the nuts on Landrover wheel bearings which with a hex nut gives you six goes and it still is impossible to get right.
Electric motors with plain bearings often have an interesting array of washers including a hardened one to bear against the bronze bearing, then perhaps a graphite filled mesh one to provide I assume an alternative thrust bearing of lower friction and then filler tufnol ones and finally the adjusting shims.
So does anyone know a supplier of these more unusual ones?
Stub Mandrel29/12/2011 20:06:58
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4318 forum posts
291 photos
1 articles
The other day I put together my steplad's christmas present shed. It used lots of plastic washers, I think these were meant to seal the holes as they deformed quite a lot. They also helped stop me overtorquing (most) of the self tappers.
 
Over four hours for a 6' x 4' shed!
 
Neil

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