Locknut vs. Standard Nut & Lockwasher 1

[kaiserman]

APPLICATION: Automotive (heavy truck); Steering & suspension hardware.

DESCRIPTION: Currently, 2, 7/16-20 threaded drawkeys secure a king pin in a heavy truck axle with standard grade 8 lockwashers and nuts.

IDEA: Replace each standard lockwasher and nut combination with a grade 8 defromed-thread hex flange locknut. Basically, the top of the deformed-thread locknut is compressed to an oval shaped locking zone. The locknuts twist freely on a bolt or stud until they make contact with the locking zone. Then they expand to an almost circular shape, creating locking compression. Locknuts are reuseable to a point.

A cost savings could be realized through the proposed hardware replacement.

To date, not 1 complaint has ever been raised regarding issues surrounding self-loosening of the king pin draw keys with the standard nut and lockwasher combination. I am attemping to locate literature stating that locknuts provide as good or better "self-loosening" properties than the standard nuts and washers.

QUESTION: Would someone please suggest hardware literature or test data that I may pursue to help me make a cost savings suggestion?


Regards,
Tim Kaiser
VW Kaiser Engineering, Inc.

http://www.vwkaiser.com

 

[MintJulep]

We have beat this to death over the years.

Start here:

faq404-1257

 

[KENAT]

So much more elegantly done than what I was going to say, star for you.

KENAT, probably the least qualified checker you'll ever meet...

 

[ewh]

(I like that emoticon...)

 

[IceStationZebra]

The short answer is that the lock nut is almost certainly less prone to loosening. I have encountered three issues with these types of nuts though:
1. They are not usually reusable (which you touched on). I believe that there is some spec that says lock nuts should be reusable up to 5 times with X% of the original locking torque, but in my experience you will only get 1 installation.
2. The clamp load will be difficult to control. Any slight variation in the nuts will result in a large change in clamp load. And obviously you will have to come up with a new torque spec (and change all the related documentation)
3. From a production stand point this type of lock nut is generally no better than a lock washer/nut combination. Instead of grabbing and installing two pieces of hardware now they have to be cognisant of putting the nut on correctly. You can eliminate this problem by using the nuts that are pinched in the middle instead.

ISZ

 

[NickE]

IceStationZebra- OP says Flange nuts, kinda have to be the right way anyway. Not that production wont put them on upside down, production is where that saying about foolproof came from.


Nick
I love materials science!

 

[IceStationZebra]

Sorry, missed that.