How many of you use helical split lock washers in bolted joints?
How many of you use helical split lock washers in bolted joints?
(OP)
Anyone want to weigh in on their pros and cons?
Tunalover
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How many of you use helical split lock washers in bolted joints?
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How many of you use helical split lock washers in bolted joints?How many of you use helical split lock washers in bolted joints?(OP)
Anyone want to weigh in on their pros and cons?
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RE: How many of you use helical split lock washers in bolted joints?
FAQ404-1257: Is a lock washer an effective torque retention device?
thread108-114051: Split Washer Placement
thread404-94197: Locking Washers
thread725-85323: Lock washers with nylock type nuts?
thread725-63343: Split lock washers - Any uses???
thread725-57042: vibration proof fasteners
thread725-145968: Lock washers on A325 bolts?
thread404-287279: Proper Use of Spring Lock Washers
thread404-230741: Studies on the use of lock washers?
RE: How many of you use helical split lock washers in bolted joints?
this link says it all for me:-
http://www.boltscience.com/pages/junkertesthelical...
RE: How many of you use helical split lock washers in bolted joints?
RE: How many of you use helical split lock washers in bolted joints?
I would never recommend one at work and I take them off things around the house.
A waste of time and money and one more component that can be left out of the assembly.
RE: How many of you use helical split lock washers in bolted joints?
Just one of many surprises when I arrived a few years ago. Change is hard. May make some progress on such issues. Had some luck on bigger problems so I have some hope.
STF
RE: How many of you use helical split lock washers in bolted joints?
Tunalover
RE: How many of you use helical split lock washers in bolted joints?
Regards
StoneCold
RE: How many of you use helical split lock washers in bolted joints?
http://www.nord-lock.com/nord-lock/wedge-locking/w...
Looks like they are 25% or so higher than generic lubed bolt torque values.
RE: How many of you use helical split lock washers in bolted joints?
Tunalover
RE: How many of you use helical split lock washers in bolted joints?
The OP asked for comments on the suitability of split lock washers in bolted joints, and the general consensus seems to be that they are ineffective. But SparWeb's comment above points out the more general problem with changing long established practices used in some companies or industries that may be suspect. Sadly, the decision to change an existing practice is usually made by non-technical management. And they are usually reluctant to implement a change that could give the impression that the existing products they have been producing and selling might be deficient.
I work in aerospace and the issue of securing threaded fasteners is taken very seriously. I have seen the opposite situation that SparWeb describes, where it is difficult to train a new-hire engineer coming from another industry to follow the very explicit and tightly controlled design practices with threaded fasteners used in aerospace.
RE: How many of you use helical split lock washers in bolted joints?
Tunalover
RE: How many of you use helical split lock washers in bolted joints?
It's as if WKTaylor wrote it, isn't it?
STF
RE: How many of you use helical split lock washers in bolted joints?
Sorry, forgot to address your last question.
I can't see how it would affect the natural frequency of the joint, provided that the bolt has been torqued the same as it would be with a regular flat washer. Unless, perhaps, something is hammering on the bolt itself... Nah I really can't picture it. Find any research on the matter?
STF
RE: How many of you use helical split lock washers in bolted joints?
My gut feeling about lowering the natural frequency is the same as yours however, I'm not sure how much of an affect it as in real terms or even if its significant, I found this paper but it refers to ordinary washers.
http://dspace.nitrkl.ac.in/dspace/bitstream/2080/1...
RE: How many of you use helical split lock washers in bolted joints?
Tunalover
RE: How many of you use helical split lock washers in bolted joints?
Although I think I understand the argument against them, and know that post-assembly wicking grade threadlocker or Nylock nuts are much more effective, we do continue to use split helical washers at present on the theory that they are somewhat better than nothing at keeping fasteners in the plant modules we ship rather than laying in the belly tarp of the truck used to ship them. That isn't proven by statistics but is not on argument in the minds of the guys who build and then re-assemble our plants at destination. That could just be superstition of course- wouldn't be the first time that something widely held as folk wisdom was proven to be untrue.
RE: How many of you use helical split lock washers in bolted joints?
As I understand it, the helical split lock washer works by creating an axial preload on the bolt/nut when it it compressed below its free height. And if this axial preload force produces sufficient friction at the thread contacts to prevent any relative movement/loosening, then it does provide some thread locking function. But unfortunately, the amount of axial preload force produced by the typical helical split lock washer, even when fully compressed, is often not sufficient to prevent loosening of a bolt/nut, especially if the joint is subject to any vibration or dynamic loading.
In aerospace, threaded fastener installations where the bolt/nut is loaded in tension often require a single fault tolerance level of reliability for the fastener locking function, which basically means each fastener must employ two separate methods of securing the threads. One common approach used to meet the single fault tolerance requirement is through a combination of using controlled installation torque to create fastener preload, and using a locking feature like a deformed section of the internal threads on the nut/insert that will continue to maintain a locking function after the loss of preload. Since a split helical washer will lose its locking function once it is no longer compressed, it is not considered a suitable form of thread locking device for aerospace applications.
Interesting topic.
Terry
RE: How many of you use helical split lock washers in bolted joints?
Mike Halloran
Pembroke Pines, FL, USA
RE: How many of you use helical split lock washers in bolted joints?
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: How many of you use helical split lock washers in bolted joints?
If if dropped to near zero clamping force, why should it not continue dropping?
--
JHG
RE: How many of you use helical split lock washers in bolted joints?
I was commenting to screwman1's post. My point was that not all joints where bolts are used will fail once the joint merely becomes loose. Some joints rely primarily on the presence of the fastener in the assembly rather than needing the fastener to be fully tightened.
Why wouldn't it continue to loosen? It certainly would! The washer in our case merely buys us time to find the loose fastener and re-tighten it rather than finding out what hole it rattled out of to end up in the belly tarp of the truck. Is that a meaningful amount of time? Dunno. That could be tradition rather than fact- but it's pretty strong tradition around here to the point of being not on argument with the folks who install our plants.
RE: How many of you use helical split lock washers in bolted joints?
Bolt Science has a page on Vibration Loosening of Bolts and Threaded Fasteners.
The force required to completely compress a spring washer is way below the tensile strength of your bolt. If the bolt has been loosened from its proper snugged down condition, the helical spring washer will slow the failure, at best.
Incidentally, I used to work with a guy who claimed that you tightened down a screw by carefully watching the helical spring washer. When the washer is compressed flat, the screw is tight. Articles that claim helical spring washers are a cause of failure, never explain the mechanism. Could this be it?
--
JHG
RE: How many of you use helical split lock washers in bolted joints?
Tunalover
RE: How many of you use helical split lock washers in bolted joints?
Despite overwhelming quantifiable evidence, despite sound engineering explanations of their worthlessness....
Many organizations have someone of sufficient influence who remembers seeing a failed joint at just the right moment before the nut fell off and concludes "Look Look! The lock washer prevented this nut from falling off!"
And apparently there is never anyone around at that moment who knows enough to point out:
"But it's a 'lock washer' and obviously it didn't 'lock' this tight"
"What good is this bolt doing now? It's rattling around. It's not holding anything"
RE: How many of you use helical split lock washers in bolted joints?