Flat washer under shakeproof -what does that achieve?

Unless you are fastening a non metalic/compressible component or bolting through a slotted hole there is no benefit from a flat washer and if then the bolt is tightened correctly there is no benefit from a shakeproof washer. If you take apart a modern car/engine you it will be rare to find any washers at all in these types of joints. Bolting plastic type materials is different .

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This thread just about sums up the engineering knowledge on here. Nixt, zilch, none, aucun. And the shameful part is that you all purport to advise on subjects to novices.
 
third engines said:
This thread just about sums up the engineering knowledge on here. Nixt, zilch, none, aucun. And the shameful part is that you all purport to advise on subjects to novices.
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Are you going to provide some useful information or just slag everyone off, even if some of the posts are open question about what had been presented as best practice by very qualified engineers?
 
third engines said:
You come over as an experienced engineer, as such you shouldn't need me to educate you. Lets hear it from you. Judging from your post #3 you aint got a clue. Subject closed.
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Yes, I am experienced. Experienced enough to know that I don't know everything. In cases where I don't know, I happily use methods and systems designed by those that do. Every once in a while I see a casual opportunity to find out. This appeared to be one of those.
As far as you are concerned it seems I was wrong.
So, on this particular subject I'll carry on implementing what is specified.
 
third engines said:
You come over as an experienced engineer, as such you shouldn't need me to educate you. Lets hear it from you. Judging from your post #3 you aint got a clue. Subject closed.
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Ok, but what about the rest of us? You have an opportunity to educate those that are interested and not experienced.
 
A spring washer keeps the bolt under tension, even if the joint moves, the bolt stretches a little, temperature etc.
So the nut is much less likely to come undone.
The flat washer has a bigger radius than the spring washer, so has more friction against the base material than it does against the spring washer. It's unlikely to rotate. It's there to avoid damaging softer metal base material usually, or to spread the load, or to provide a regular surface for the shakeproof washer to work on. E.g. if the surface of the base part is not machined.
 
lw395 said:
A spring washer keeps the bolt under tension, even if the joint moves, the bolt stretches a little, temperature etc.
So the nut is much less likely to come undone.
The flat washer has a bigger radius than the spring washer, so has more friction against the base material than it does against the spring washer. It's unlikely to rotate. It's there to avoid damaging softer metal base material usually, or to spread the load, or to provide a regular surface for the shakeproof washer to work on. E.g. if the surface of the base part is not machined.
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My observation is that the ends of the spring washer dig in slightly so giving some locking although the compressive compliance does also tend to maintain the compression in the event that something stetches a bit. I don't know about modern car engines ...haven't rebuilt one since 1982 although that one's still running well.
 
lw395 said:
A spring washer keeps the bolt under tension, even if the joint moves, the bolt stretches a little, temperature etc.
So the nut is much less likely to come undone.
The flat washer has a bigger radius than the spring washer, so has more friction against the base material than it does against the spring washer. It's unlikely to rotate. It's there to avoid damaging softer metal base material usually, or to spread the load, or to provide a regular surface for the shakeproof washer to work on. E.g. if the surface of the base part is not machined.
Click to expand...
+1
Modern car nuts often have a built in flange (AKA flat washer) to spread the load on the base material. The nuts also are frequently self locking (use once versions)
 
lw395 said:
A spring washer keeps the bolt under tension, even if the joint moves, the bolt stretches a little, temperature etc.
So the nut is much less likely to come undone.
The flat washer has a bigger radius than the spring washer, so has more friction against the base material than it does against the spring washer. It's unlikely to rotate. It's there to avoid damaging softer metal base material usually, or to spread the load, or to provide a regular surface for the shakeproof washer to work on. E.g. if the surface of the base part is not machined.
Click to expand...

Question was shake proof washer not spring.

A flat washer under a shake proof negates the advantage of a shake proof.

So it is poor engineering to fit like this.
 
The flat washer has a bigger radius than the spring washer, so has more friction against the base material than it does against the spring washer. It's unlikely to rotate. It's there to avoid damaging softer metal base material usually, or to spread the load, or to provide a regular surface for the shakeproof washer to work on. E.g. if the surface of the base part is not machined.[/QUOTE]

I'll hang my hat on this being the reason. Fine if the base material is soft plastic or irregular surface there's good reason for the larger flat washer. Too often I've seen them fitted in circumstances where i would not consider them advantageous and may even increase the likelihood of the fastening becoming loose.
I'll now brace myself for the broadside from "third engines" when he tells us the real reason. hehe.
 
What’s a shake proof washer? There are many types and some are used with washers, some not. RFI.

Go to www.dropsonline.org and download reliable securing. Spring washers are shit.
 
Last edited by a moderator:
paulajayne said:
Question was shake proof washer not spring.

A flat washer under a shake proof negates the advantage of a shake proof.

So it is poor engineering to fit like this.
Click to expand...

There are many sorts of 'shakeproof' washer and many engineering problems.
There are times when proper engineers who know what they are doing, specify a flat washer with some sort of shakeproof under the nut.
Many types of serrated shakeproof washers are made of spring steel and work as diaphragm springs.
If you've ever had trouble getting a product through qualification, including vibration testing, you'd know that some things are counter-intuitive.
 
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