Lockwashers are used under bolt heads or nuts to increase the bearing area or offer greater hardness, so that the nut or bolt can be rotated without distortion of the bearing surface. There are two basic styles of lockwasher, split and tooth.
Also called the Helical Spring Lock Washer, the surface is bent or crimped so that the shape will prevent loosening under stress. The Split Lock Washer features a gap cut into its circumference. The High Collar Lock Washer is used with socket head cap screws.
On Tooth Lock Washers jagged teeth are cut into either the inner or outer diameter, or both diameters. These teeth are used to integrate the bolts into one or more component assemblies.
There are four principal tooth lockwasher styles:
External Lock Washer: Jagged teeth rim the outer diameter.
Internal Lock Washer: Jagged teeth rim the inner diameter.
Internal-External Lock Washer: Jagged teeth rim both the inner and outer diameters.
Countersunk Lock Washer: These are used under bolt heads to increase the bearing area or offer greater hardness. Jagged teeth rim the outer diameter of the countersunk lockwasher. The teeth and lockwasher rim are raised, jutting upward at an angle as well as outward. These are used to lock the bolts fast when the lockwasher is used as part of a component assembly.