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Grades of inch prevailing torque locknuts, all metal (three common marking methods)
On prevailing torque locknuts, the grade of nut is identified by one of three different sets of markings that denote the
strength level and manufacturer.
Common prevailing torque locknut grade identification markings
Grade identification marking
INTRODUCTION
Grade B (hex nut) and Grade F (flange nut)
Three raised or indented dot marks
(Marks do not have to be in corners.)
Grade C (hex nut) and Grade F (flange nut)
Six raised or indented dot marks
(Marks do not have to be in corners.)
One circumferential notch on all six corners
Two circumferential notches on all six corners
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Grade
Marking description
Grade A
No marks
Grade A
No letter mark on side flat
Grade B
Letter B on side flat
Grade C
Letter C on side flat
Grade A
No notches
Grade B
Grade C
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