TM-9-2350-311-34-1 Maintenance Manual for Volume 1 M109 Hull Download
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TM 9-2350-311-34-1 E-5 FASTENER GRADE In addition to thread type classification, threaded fasteners are also classified by material. The most familiar fastener classification system is the SAE grading system (Table E-4). TABLE E-4 SAE SCREW AND BOLT MARKINGS SCREWS BOLTS SAE grade 2 SAE grade 6 No marking Four radial dashes 90° apart SAE grade 3 Two radial dashes SAE grade 7 180° apart Five radial dashes 72° apart SAE grade 5 Three radial dashes SAE grade 8 120° apart Six radial dashes 60° apart Markings on Hex Locknuts Grade A — no marks Grade B — three marks Grade C — six marks Grade A — no notches Grade B — one notch Grade C — two notches Grade A — no mark Grade B — letter B Grade C — letter C E-5/(E-5 blank)