McMaster 95030A270 Low-Strength Steel Locknut, Pack of 10, for Cotter Pins, Zinc-Plated Steel, 3/4"-16 Thread Size

Use these locknuts to secure rotating parts subjected to mild vibration, such as the wheels on carts and hand trucks. They're not recommended for use on parts exposed to high vibration because the pin can shear under prolonged stress. These nuts are reusable, but you'll need a new cotter pin (not included) with each use.

Low-Strength Steel — Rated Grade 2, Class 6, or lower, these locknuts are about half as strong as medium-strength steel nuts. Use them with screws that have a similar strength rating to avoid stripping threads during installation.

Zinc-Plated Steel — A step up from plain steel, the zinc plating withstands occasional exposure to moisture.