TM-9-2350-311-20-1

HOWITZER, MEDIUM, SELF-PROPELLED, 155MM; M109A2, M109A3, M109A4 AND M109A5

TECHNICAL MANUAL; UNIT MAINTENANCE MANUAL FOR HULL, POWERPLANT, DRIVE CONTROLS, TRACKS, SUSPENSION, AND ASSOCIATED COMPONENTS

AUGUST 1994

TM-9-2350-311-20-1 - Page 1162 of 1275

TM9-2350-311-20-1

F-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 F-4).

TABLE F-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 A — no mark

Grade B — three marks

Grade B — letter B

Grade C — six marks

Grade C — letter C

Grade A — no notches

Grade B — one notch

Grade C — two notches

F-5/(F-5 blank)