1/4 MS35335, Military External Tooth Lock Washer 410 Stainless Steel DFAR FSP The nut has a 1/4-20

The nut has a 1/4-20 thread size and a 7/16" diameter

but it also provides less holding power

10-16 x 3/4 Phillips Pan Thread Cutting Screw Type 25 Fully Threaded Zinc:

They are 1/2 inch long and have a diameter of 4-24

and the self-piercing needle point allows for easy installation without the need for pre-drilling

1/4 MS35335, Military External Tooth Lock Washer 410 Stainless Steel DFAR FSP The nut has a 1/4-201 4 MS35335 Military External Tooth Lock Washer is a type of fastener used to prevent loosening of bolted joints due to vibration or other dynamic loads. It is made of 410 stainless steel for corrosion resistance and durability. The washer has external teeth that bite into the mating surface to create a secure hold. It conforms to the Military Specification MS35335 and is DFAR compliant, ensuring compliance with US Department of Defense (DoD)