TM 9-243TYPES AND USES - ContinuedTRAMMELSThe trammel measures distances beyond the range ofcalipers. The instrument consists of a rod or beam (1) towhich trams (2) are clamped. The trams (2) carrychucks (3). The trammel can also be used as a dividerby changing the points.READING A VERNIER CALIPERTo read a vernier caliper, you must be able to under-rule (1) is graduated in 0.025 of an inch. Every fourthdivision (2) (representing a tenth of an inch) is num-stand both the steel rule and vernier scales. The steelbered.The vernier scale (3) is divided into 25 parts and num-bered 0, 5, 10, 15, 20, and 25. These 25 parts are equalto 24 parts on the steel rule (1). The difference betweenthe width of one of the 25 spaces on the vernier scale (3)and one of the 24 spaces on the steel rule (1) is 1/1000of an inch.Read the measurement as shown above.Read the number of wholeinches on the top scale (1) tothe left of the vernier zeroindex (4) and record. . . . . . . . . . . . . . . . . 1.000 inchzero index (4) and recordRead the number of tenths (5). . . . . . . . . . . .0.400 inchRead the number of twenty-fifths (6)to the left of the vernierbetween the tenths mark(5) andthe zero index (4)and record. . . . . . . . . . . . . . . . .3 x .025 = .075 inchRead the highest line on thevernier scale (3) which lines upwith the lines on the topscale (7) and record. (Remember1/25 = .001 inch) . . . . . . . . . . 11/25 or 0.011 inchTOTAL1.486 inches6-4
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