Ginch: Thanks for that info and link. I have one of these nuts I got from SIP/DRT a while back but never used, #11351940. Scootermercato sells what appears to be the same one... both retail approx $10. SIP has another option without the washer for 1/3 the price.... I'm sure there are others out there
I wonder if these are actually true "Jet Nuts" as they come with a toothed lock washer. Or are they simply machined "flange nuts" with NO self locking characteristics...
Some more detailed information about the Jet/K nut and how it achieves the self locking through Eliptical offset on part of the threads., As you said Ginch!
Jet-Nut / K-Nut - from wiki
A jet nut, also known as a k-nut, is a special type of hex locknut that is commonly used in the aerospace and automotive racing industries.
It has a flange on one end of the nut, the hex is smaller than a standard sized hex nut, and it is shorter than a standard hex nut. It achieves its locking action by using an elliptical offset on the un-flanged end of the nut.
Elliptical offset nuts
Elliptical offset nuts is a catch-all category that encompasses designs known as oval locknuts or non-slotted hex locknuts,. The salient feature is that the threadform has been deformed at one end so that the threads are no longer perfectly circular. The deformed end is usually shaped into an ellipse or obround triangle. These are known as one-way nuts as the nut may be easily started on the male fastener from the bottom non-deformed portion, but are practically impossible to start from the deformed end. As the male fastener reaches the deformed section it stretches the threads of the nut elastically back into a circle. This action increases the friction between the nut and the fastener greatly and creates the locking action. Due to the elastic nature of the deformation the nuts can be reused indefinitely.
Reusing Locking Nuts
The FAA has issued guidelines on the reuse of locking nuts. Specific recommendations have been published for larger sizes (7/16-20 and up), but the general rule is that you should not be able to turn the nut by hand once the locking portion engages the male threads. If you can turn the nut with your fingers, it must be replaced. When in doubt, replace!
On a slightly different note: digging into thread locking/bolt lossening on Boltscience.com. Interesting stuff for a Geek if you want to dive in deep! Basicly they say that split-ring washers do NOT help secure a nut, and actually cause it to fail sooner than just a plain nut alone. This is only preliminary research. Not thinking specifically for the clutch, just general purpose info for those who want to dig deeper. I think I shall