Has any body seen officially why DIN 127 etc lockwasher stds were withdrawn ? 2

[Tmoose]

Over the past 10 or 15 years various DIN standards for locking washers and similar hardware have been "withdrawn" and often not replaced.



Different entities ( mainly companies that sell specialty lockwashers ) generally make the claim that the various standards were withdrawn due to "ineffectiveness" at preventing loosening when subjected to dynamic and even static loads.

I do not dispute the questionable efficacy of split lockwashers, etc at actually preventing loosening.

But so far I have not seen any DIN documents saying why the various standards were withdrawn.


Has any body seen officially why DIN 127 etc lockwasher stds were withdrawn ?

 

[MintJulep]

See page 26

https://www.wuerth-industrie.com/we...d_center/Broschuere_DIN-EN-ISO_Normung_DE.pdf

for more of what you already know.

 

[MGZmechanical]

Well, there're many tests regarding that. See:

http://www.boltscience.com/pages/helicalspringwashers.htm

And in the ASME B18.2.1 it says:

NOTE: The word lock appearing in the names of products in this Standard is a generic term historically associated with their identification and is not intended to imply an indefinite permanency of fixity in attachments where the fasteners are used.

For lock washers see DIN 6796 and DIN 25201
Best regards

 

[Tmoose]

Thanks ManoloGalarraga,

Regarding the Junkers tests, I think sliding a component back and forth a mm or so, with ball bearings in between the "clamped" bolted surfaces is not a particularly realistic test.

http://www.novatechloadcells.co.uk/eng/e036.htm

 

[dik]

Catch the thread:

thread404-230741

and the FAQ:

FAQ404-1257

Dik

 

[3DDave]

If the DIN standards are like other standards I've come across, there needs to be a sponsor who is willing to make a contribution to keep it in play. The frequent point of standards is to assure the general user base that the parts made to these standards will be available from multiple sources, but the reality is that often one source is so much better/cheaper that no one else really competes. It's possible that no one making the parts feels like being standardized is worth paying for anymore.

 

[drawoh]

Tmoose,

At my new job here, I have pointed out that helical spring lock washers are not regarded as locking devices. I have been informed that our screws are installed with calibrated power tools to known torques. Under vibration testing, done in-house, the fasteners with helical spring lock washers stay tight. The fasteners without lock washers tend to some loose.

They also use the small hex socket flat head and button head cap screws, that I detest. They have no problems stripping sockets. Production hates Phillips sockets. Again, everything is installed with controlled torque.

--
JHG

 

[SwinnyGG]

I wouldn't believe anyone who says they can prove that helical washers work until I've seen the data.

 

[SwinnyGG]

Regarding the Junkers tests, I think sliding a component back and forth a mm or so, with ball bearings in between the "clamped" bolted surfaces is not a particularly realistic test.

With regard to modeling the behavior of a joint subject to vibration, I'd say it about as close as you're going to get.

 

[3DDave]

If the screws are holding down sheet metal or other thin sections then I am not surprised. Adding to the stack and increasing the bearing area are helpful. The same effect should be had with plain washers of the same thickness.

 

[drawoh]

3DDave,

Are you responding to me? Most of the stuff here is sheet metal.

--
JHG

 

[MikeHalloran]

If you can keep your MBAs busy counting lockwashers, they won't have so much time to meddle with other stuff.


Mike Halloran
Pembroke Pines, FL, USA

 

[Tmoose]

If an an assembly was subjected to loads alternating somewhat sinusoidally from tension to transverse, with frequenc ranging from 200 to 300 Hz or so, would that qualify as vibration ? These bolted assemblies routinely survived test sessions just like that lasting about 1.5 hours and thus accumulating 1,000,000 or so cycles without failure.

http://1.bp.blogspot.com/_mGrjzceHfJM/TPo1cnpmp1I/AAAAAAAAAPU/PMh_BWl6h-Q/s1600/DSCN2442.JPG

http://1.bp.blogspot.com/-A7NRHWZFXIw/ULHQfBTOIkI/AAAAAAAAAwQ/IAmIG-CG6WQ/s1600/DSCN3107.JPG

I guess somebody forgot to install the Nord-lock wshers for the photo shoot.

 

[SwinnyGG]

Well for one thing... rod cap bolts don't see any loading other than tension.

And 2... anyone who knows anything about fasteners will tell you that the first solution is always sufficient preload. If you apply enough preload, and maintain that preload in operation, fasteners don't come loose.

An assembly like a rod cap doesn't need additional locking because they are designed with careful attention to preload, and the components are stiff enough that preload relaxation isn't a problem.

 

[dhengr]

Other than that most of them don’t work very well much of the time, which is pretty well spelled out in the footnotes to Tmoose’s OP attachment as a reason; and also by many tests over the years, and also sad field experience which show they don’t work as advertised, I’d say that’s fairly official. I think it is a grand conspiracy against the lock washer makers, by the flat washer guys, and the people who sell torques by the five gal. bucket. They probably didn’t pay their DIN Dues, so now they are in Deep DIN DoDo.

 

[RolMec]

The official reasoning runs on two main rails:
1) If possible, a correctly designed and assembled bolted connection should not require additional securing elements to be functional.
2) An elastic / spring type securing element can only be functional within a bolted connection, if it is able to compensate the loss of clamping force due to embedding. For HT bolted connections (quality 8.8 and above), the washers as per DIN 127 etc. could not achieve this (only exception from the "old" range of options were washers as per DIN 6796). So, the different securing washers as e.g. of DIN 127 were withdrawn for general use but re-emitted for use in bolted connections of lower strength (below quality 8.8), pls. e. g. refer newer DIN 128. The tech. statement ~ #2) can be found in the comments.

Roland Heilmann
Lpz FRG