Grade-C Automation Lock Nut: An all-metal, one-piece hex nut which derives its prevailing torque characteristics from controlled distortion of its top threads from their normal helical form to a more elliptical shape.
Grade-GT Flange Style Automation Lock Nut: Similar to Grade-C but with a flange on the bottom side of the nut.
Grade-C: These nuts are reusable and con withstand temperatures of up to 450°F. Can withstand severe vibration and shock leads. Frequently used in farm machienery, plus the automotive and related metalworking industries.
Grade-GT: Has a lower, more uniform bearing stressto clamp force ratio. This style reduces inventor (by eliminating a washer) and in-place cost. It is designed to be used specifically but not exclusively with grade-8 frame bolts.