Tooth (or Star) Lockwashers

Here is an excerpt from NASA Ref Publication."Fastner Design Material" 

"Tooth lockwashers are used with screws and nuts for some spring action but mostly for locking action. The teeth are formed in a twisted configuration with sharp edges. One edge bites into the boltbead (or nut) while the other edge bites into the mating surface. Although this washer does provide some locking action, it damages the mating surfaces. These scratches can cause crack formation in highly stressed fasteners, mating parts, or both, as well as increased susceptibility to corrosion."

Use Case: Ground Bar Mounting with Tooth Lockwashers

Tooth (or star) lockwashers have been employed to mount the ground bar onto a powder-coated backpanel. In this application, the sharp, twisted teeth of the washer intentionally bite into the coated surface, disrupting the insulating powder layer to establish direct metal-to-metal contact. 

While this mechanical action does introduce surface scratches—typically considered detrimental in high-stress or corrosion-prone environments—it is leveraged here to enhance electrical conductivity between the ground bar and the enclosure. The washer’s locking function also contributes to mechanical stability, ensuring reliable grounding over time.

Here is a reference image from Saginaw

Here are the additional resources I found useful:

Spring or Star Washers for Earthing Stud? - Unit 3 Compliance

Fastener Design Manual

SCE-101966 - Saginaw Control and Engineering