On 12/29/2022 7:14 AM, Jeff Green wrote:
NASA: Split Lock Washers Are "Useless"!
Many years I ago I worked at NASA building space flight hardware. This hardware was launched on the Shuttle, so it had to withstand Shuttle launch vibration. It was installed on the International Space Station and needed to last for years...so it was built (overbuilt?) to a very high standard.
I can't recall a single instance of our hardware using any form of locking washer - split, star, interference, or friction-locking (Nylock). Everything used locking Helicoil (or similar) threaded inserts or some form of thread-locking compound like Loctite or Vibra-tite.
In my current career in military aviation, I've seen split lockwashers on MANY pieces of aircraft avionics. Some of the gear I've handled went thru MIL-STD-810 qualification for vibration... Some of the gear I've handled was been literally back from a warzone. I've never seen loose hardware due to a locking washer failure. (Now, I have seen split washers literally split in half upon removal on some vintage WWII gear I've worked on...)
That said, all of the important stuff like driveshaft bolts, etc., use locking methods that are much more robust than split washers. :)
I think the bottom line is to think about what you're doing and the severity of the failure. For our ham-radio stuff, split washers are fine. For a turbine engine fuel control, it's not. For something going to space, it's not.
thanks much and 73,
ben, kd5byb
Ben Hall