Lon nan Gruagach
Active member
Wot? Like use a smaller hammer??? I don't believe you
Flat washer under shakeproof -what does that achieve?
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Wot? Like use a smaller hammer??? I don't believe you
Heckler
Active member
Depends on the application. Could be to spread the load and prevent damage to the base material. For example the keel bolts on my Bene have extra wide and thick washers to spread the load on the fi glass. There are different spring washers for different applications. The ones with an edge to dig in are one sort, then the wavy multi edge ones for another. Recent engines have built in to the bolt heads different locking mechanisms and are use once. The Perkins I rebuilt for the PBO article didn't have any washers at all, just formed bolt heads, and that is an engine designed in the 80s. So use what the designer used originally, also if using spring washers off any type, replace them, they deform after they have done their job and are undone.
Heckler
Active member
Back of net
lw395
Well-known member
jwilson
Well-known member
I'm not an engineer but I've always assumed that in situations where you don't want it coming undone accidentally (hence need a shake-proof washer) but may want it deliberately undone and refitted many times, that a flat washer stops the surface under it getting cut up by the sharp edges of the shake-proof washer, and as others have said, spreads the load. Eventually you may need a new shake-proof washer, but the fitting and flat washer will be re-usable. Sounds like good engineering to me, the more so the softer, more easily damaged the underlying item is.
solent clown
RIP
there are many types of shakeproof washers, but to simplify, most are a slightly conical shape with serrations. The conical shape acts as a preload spring, and the fserrated face acts as mechanical lock. One could argue for using a washer underneath to protect material, or one could use the shakeproof washer the other way up. We use shakeproof washers with larger washers underneath on some panels that are liable to flexing. For instance we make punched aluminium seats that take up the drivers shape when they are occupied (think deck chair but in metal instead of fabric) If we do not spread the load then we end up with fracturing at the holes. There are also reasons such as load spreading with things like roof racks, ladders, grab handles where the engineers might choose to do so. Some surfaces, either painted or plastic coated can deform and negate the effect, both mechanical and tension, of a shakeproof washer, so there are many reasons for different solutions.
Yes I am an engineer, yes I am highly qualified and experienced. No I do not know everything, I was in R+D for a long time, but fastenings were "incidental" and down the food chain as it were. What I have said here is our actual use in real life doing exactly what the OP asked about, so if someone comes back with a better explanation then excellent.
I would add they are not a magic bullet, if there is movement or distortion they can and will work loose. They depend on being clamped tight and the workpiece also being clamped without movement.
Yes I am an engineer, yes I am highly qualified and experienced. No I do not know everything, I was in R+D for a long time, but fastenings were "incidental" and down the food chain as it were. What I have said here is our actual use in real life doing exactly what the OP asked about, so if someone comes back with a better explanation then excellent.
I would add they are not a magic bullet, if there is movement or distortion they can and will work loose. They depend on being clamped tight and the workpiece also being clamped without movement.
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D
Deleted member 36384
Guest
A video of some vibration proof fasteners being subjected to Junkers Vibration Table testing. Note how shit a spring washer is:-
https://youtu.be/cg78FIZR3Xc
https://youtu.be/cg78FIZR3Xc
RichardS
N/A
I've never used a new shakeproof washer, other than to replace one which is already in place, and they usually seem to be used without flat washers. I do use a lot of spring washers though, and usually use those alongside a flat washer to spread the load. I've no idea whether that is best engineering practice, although it has always worked for me. 
Richard
Richard
solent clown
RIP
I only use them as I have a couple on the shelf... One day I will get Karen to count them Those boxes are 3 inches deep....
IMG_20180709_100423[1] by mark punksteel, on Flickr
Those boxes are 3 inches deep....IMG_20180709_100423[1] by mark punksteel, on Flickrlw395
Well-known member
It's silly to say 'spring washers are shit', they do a good job in a huge number of applications.
In certain special applications, you need something different.
For instance on my bike, the clutch nut is held on by Nordlock washers, presumably because a spring washer isn't up to the task.
But that pair of Nordlock washers costs over a quid at trade price.
Incidentally, they have smooth faces presented to the nut and the bit they clamp to the shaft.
Sometimes of course, what you need is some Loctite.
D
Deleted member 36384
Guest
It’s not silly. Where vibration is a risk to fastener integrity the worst choice is a spring washer. They do not work as demonstrated by testing, compare the nut only and nut / springwasher tests, hardly any difference.
dmayes
Member
A fat washer would spread the load, so if the hole is bigger than the bolt a flat washer may be needed. I would use a nyloc nut instead of the shake proof washer. This would give a secure join independent of the washer used. Apologies if my diy knowledge is not up to experts in the BBC,
macd
Active member
I suspect third engines must be part of some ancient guild, so secretive is he of 'best practice'.
I can say that in the highly successful motorcycle endurance race team I was once part of, washers of any sort on external components were relatively rare, flange nuts having become common by the eighties. If a washer was used, it was never the spring or shakeproof variety, just a plain one...taken to the correct torque, and the appropriate threadlock applied to clean threads. Critical components were lock-wired. As you can imagine, there's a plenty of opportinity for things to work loose in 24 hours at 10,000rpm-plus. In almost a decade, I can't recall anything falling off except the riders.
I can say that in the highly successful motorcycle endurance race team I was once part of, washers of any sort on external components were relatively rare, flange nuts having become common by the eighties. If a washer was used, it was never the spring or shakeproof variety, just a plain one...taken to the correct torque, and the appropriate threadlock applied to clean threads. Critical components were lock-wired. As you can imagine, there's a plenty of opportinity for things to work loose in 24 hours at 10,000rpm-plus. In almost a decade, I can't recall anything falling off except the riders.
solent clown
RIP
LadyInBed
Well-known member
Not a mechanical engineer, just an enthusiastic amiture, I have gone over to using nylock nuts (with a washer). They appear to do a good job but not if there is a lot of heat involved
The shake proof washers that I've come across had either internal teeth or external teeth (star washers). I assume that they do different jobs, or are they interchangeable?
The shake proof washers that I've come across had either internal teeth or external teeth (star washers). I assume that they do different jobs, or are they interchangeable?
lw395
Well-known member
Both failed in that test.
A test that requires an advanced product. Or Loctite.
I've used spring washers and put products through 'shake and bake' military approval tests. They have their uses. Which is why millions of them are used every day.
PuffTheMagicDragon
Active member
It is quite some time that I have been retired. Be that as it might, I could not help looking back remembering some engineers I have worked with and musing about the differences between third engineers and those who were established chiefs.
Perhaps the clue lies in the name nom de plume 'thirdengines'...
Perhaps the clue lies in the name nom de plume 'thirdengines'...
Jaguar 25
Member
This just shows that the spring washer used was unsuitable for the specific application tested. It does not mean that spring and shakeproof washers have no place in equipment design!
greeny
Well-known member
Just a thought, what if the bolt was left hand thread, would it need a left hand spring or serated washer?
mlines
Active member
So you have never tried to remove a U-Joint from a Yoke with a large hammer? Lay the propshaft along your arm with the U-Joint hanging loose off the end of you hand, then tap the base of the yoke with a small hammer, the UJ will walk gradually out. Hit it with a large hammer and it will not move at all.
