TM-9-2350-311-34-2 Maintenance Manual for Volume 2 M109 Cab Download
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TM 9-2350-311-34-2 D-5 FASTENER GRADE In addition to being classified by thread type, threaded fasteners are also classified by material. The most familiar fastener classification system is the SAE grading system (Table D-4). Table D-4 SAE SCREW AND BOLT MARKINGS SCREWS BOLTS SAE grade 2 SAE grade 6 No markings Four radial dashes 90° apart SAE grade 3 SAE grade 7 Two radial dashes Five radial dashes 180° apart 72° apart SAE grade 5 SAE grade 8 Three radial dashes Six radial dashes 120° apart 60° apart MARKINGS ON HEX LOCKNUTS Grade A - no marks Grade B - three marks Grade C - six marks Grade A - no marks Grade B - letter B Grade C - letter C Grade A - no notches Grade B - one notch Grade C - two notches D-6