3 ms·

This is exactly the kind of know-it-all behavior I am complaining about. It is beyond a condemnation that a professional such has yourself has not developed a

This is exactly the kind of know-it-all behavior I am complaining about. It is beyond a condemnation that a professional such has yourself has not developed a sense for "authority X recommends Y but everybody is doing Z, there's probably a reason for that". Split lock washers persist because they are a cheap way to get a decent amount of preload into a bolted joint without torquing the bolt very much relative to typical torque values for fasteners of that size. For highly price sensitive widgets where the nature of the joint means it flex/vibrate too much for "nothing" to not be a acceptable solutions split lock washer is often the cheapest acceptable solution. I understand why NASA says "no locking value". That's a fine rule of thumb for what they do. But they're not making value priced widgets. Having a fastener maintain preload has "locking" value in many practical real world applications.

mhb 4y ago
It could be that you're right, but presenting as evidence that everyone is doing a thing is hardly compelling. Everyone is wearing cloth masks. Everyone is "investing" in crypto. See why "everybody is doing Z" might not be the greatest heuristic?
mhb 4y ago
Let's do something crazy and look at what actually happens with a vibrated split washer[1]. Maybe you can explain how this demonstration differs from the situations in which you are asserting the split lock washers are effective. Is this hardware not crappy enough to be used in the "value priced widgets" where the washers work? [1] https://www.boltscience.com/pages/helicalspringwashers.htm https://www.boltscience.com/pages/helicalspringwashers.htm
mlyle 4y ago
I've done quantitative testing on shake tables and I've not seen any situation in which split lock washers yield a benefit-- low torques, high torques, rigid assemblies, assemblies with a decent spring constant and flex in them, etc. I didn't believe that conventional wisdom could be so wrong-- but they either break even within my ability to measure or do worse. I omit them whenever I can, now. Tooth lock washers are pretty bad, too-- though sometimes they are slightly beneficial. I don't think they're generally worth the surface damage they cause for minimal benefit. Mostly, you can ignore any locking device. And if you need one, a nylock nut, or a threadlocker crayon, or a wedgelocking nut, etc, is infinitely superior. (And of course, there's castellated nuts and safety wire for really critical stuff).
kazinator 4y ago
There is not always a reason. Onions in the varnish are a thing; and spring lock washers are exactly that. A bolt being tightened all the way and then some is what constitutes preload. A bolt connects two parts via preload: the tension in the bolt. You must overcome that much force to separate those parts. The bit of tension in some dainty washer before the bolt is tightened means absolutely nothing. If there were some application that for some strange reason requires a very light torque, the washer could be useful; but it wouldn't be locking anything. How it could be useful is by creating a softer range of torque: a range where the torque increases slowly relative to the turn rate. A bolt normally has no torque until it's tightened all the way, and then rapidly rising torque from there. The washer could create a more rounded knee there; and the only possible reason that would ever be useful is if the application stayed in the operating area of that knee! There are devices in which a nut compresses a spring to a variable amount, like preload in suspensions, or resistance in exercise equipment and such. That is not a fastener application; it has nothing to do with locking.
- throwaway0a5e 4y ago
  >The bit of tension in some dainty washer before the bolt is tightened means absolutely nothing. Only if you restrict yourself to the "real engineering" that the internet loves. >and the only possible reason that would ever be useful is if the application stayed in the operating area of that knee! Which is frequently what happens when you try and build shit out of slip fit "what's the thinnest wall tubing we can get away with" held together with bolts acting as pins and the assembler is expected to just kinda eyeball it and not crush the tube lock washers are beneficial. We ship with nylocks now though because the extra part count is more expensive than the difference between nylock and split washer at our volume. >There are devices in which a nut compresses a spring to a variable amount, like preload in suspensions, or resistance in exercise equipment and such. That is not a fastener application; it has nothing to do with locking. This is just an argument of semantics/taxonomy. See also: belville washer or spring washer.
  - mhb 4y ago
    So finally we come to what you could have made clear from the start without the desultory, time-wasting back and forth. The industry in which you are involved and for which you would not consider hiring someone who believes objective data is one in which you imagine there is some benefit to lock washers in assembling crap. It sounds as though you are using lock washers as a compliant element to avoid crushing fragile components rather than to prevent unscrewing - so outside the scope of this discussion.

mhb 4y ago

It could be that you're right, but presenting as evidence that everyone is doing a thing is hardly compelling. Everyone is wearing cloth masks. Everyone is "investing" in crypto. See why "everybody is doing Z" might not be the greatest heuristic?

mhb 4y ago

Let's do something crazy and look at what actually happens with a vibrated split washer[1]. Maybe you can explain how this demonstration differs from the situations in which you are asserting the split lock washers are effective. Is this hardware not crappy enough to be used in the "value priced widgets" where the washers work? [1] https://www.boltscience.com/pages/helicalspringwashers.htm https://www.boltscience.com/pages/helicalspringwashers.htm

mlyle 4y ago

I've done quantitative testing on shake tables and I've not seen any situation in which split lock washers yield a benefit-- low torques, high torques, rigid assemblies, assemblies with a decent spring constant and flex in them, etc. I didn't believe that conventional wisdom could be so wrong-- but they either break even within my ability to measure or do worse. I omit them whenever I can, now. Tooth lock washers are pretty bad, too-- though sometimes they are slightly beneficial. I don't think they're generally worth the surface damage they cause for minimal benefit. Mostly, you can ignore any locking device. And if you need one, a nylock nut, or a threadlocker crayon, or a wedgelocking nut, etc, is infinitely superior. (And of course, there's castellated nuts and safety wire for really critical stuff).

kazinator 4y ago

There is not always a reason. Onions in the varnish are a thing; and spring lock washers are exactly that. A bolt being tightened all the way and then some is what constitutes preload. A bolt connects two parts via preload: the tension in the bolt. You must overcome that much force to separate those parts. The bit of tension in some dainty washer before the bolt is tightened means absolutely nothing. If there were some application that for some strange reason requires a very light torque, the washer could be useful; but it wouldn't be locking anything. How it could be useful is by creating a softer range of torque: a range where the torque increases slowly relative to the turn rate. A bolt normally has no torque until it's tightened all the way, and then rapidly rising torque from there. The washer could create a more rounded knee there; and the only possible reason that would ever be useful is if the application stayed in the operating area of that knee! There are devices in which a nut compresses a spring to a variable amount, like preload in suspensions, or resistance in exercise equipment and such. That is not a fastener application; it has nothing to do with locking.

throwaway0a5e 4y ago
>The bit of tension in some dainty washer before the bolt is tightened means absolutely nothing. Only if you restrict yourself to the "real engineering" that the internet loves. >and the only possible reason that would ever be useful is if the application stayed in the operating area of that knee! Which is frequently what happens when you try and build shit out of slip fit "what's the thinnest wall tubing we can get away with" held together with bolts acting as pins and the assembler is expected to just kinda eyeball it and not crush the tube lock washers are beneficial. We ship with nylocks now though because the extra part count is more expensive than the difference between nylock and split washer at our volume. >There are devices in which a nut compresses a spring to a variable amount, like preload in suspensions, or resistance in exercise equipment and such. That is not a fastener application; it has nothing to do with locking. This is just an argument of semantics/taxonomy. See also: belville washer or spring washer.
- mhb 4y ago
  So finally we come to what you could have made clear from the start without the desultory, time-wasting back and forth. The industry in which you are involved and for which you would not consider hiring someone who believes objective data is one in which you imagine there is some benefit to lock washers in assembling crap. It sounds as though you are using lock washers as a compliant element to avoid crushing fragile components rather than to prevent unscrewing - so outside the scope of this discussion.