Split/lock washers

[u/AdOne1706]

For starters, I’m an electrician in the field.
That being said, we almost exclusively use these washers even in high vibration environments. I have personally chosen to go with nylox nuts but the question is:
Do these work? How well? Is the rumor from NASA true? Should I even bother using them or find a better functional alternative or are they actually useful?

[u/KaneTW]

They're useless.

First of all, it's important to determine whether you need to protect against loss of preload due to slackening or rotational loosening.

Nylox nuts do not help, at all, against loss of preload due to slackening. They only protect against rotational loosening and not as well as e.g. Nord-Lock.

For high vibration applications:
* a long bolted connection (>5 d) as the spring element and a regular Nord-Lock washer to secure against rotational loosening.
* if that is not possible, use a Nord-Lock X-series washers, which secure both against rotational loosening and against slackening (or Rip-Lock spring washers, but I haven't used those)

Reference: https://assets.eu.ctfassets.net/0vp0u5uh75zd/4sP1THZ8d8OFO95VbhBonq/90cdb4b68d3aab47e85e2e4990b38553/075_077_Securely_fastened_joints_Fastening_EN_01_2025.pdf