TM 9-243Chapter 3 READING MEASURING SCALESThe following chapter is designed to provide a basicunderstanding of how to read scales, dials, and gages. Itwill not provide any information on the actual use of thetools. Reference to this chapter will be made throughoutthe remainder of the manual.INDEXItemPageReading the scale of a rule or tape. . . . 3-1Reading a metric rule. . . . . . . . . . . . . . . . 3-3READING THE SCALE OF A RULE OR TAPEThe more common type rules and tapes are divided intofractions, inches, and feet. Explained here are thescales on a 12-inch steel machinist’s rule.The rule is divided into twelve inches. The inches arefurther divided into eighths, sixteenths, thirty-seconds,and sixty-fourths.Look at the rule. There is a small numeral marked on theend of the rule nearest the l-inch mark. This numeralindicates the number of divisions per inch.When referring to fractions, always use the reducedname. This is the smallest numerator (top number) anddenominator (bottom number). For example, 3/6 can bereduced to 1/2 by dividing both the top and bottom by 3.Generally, fractions may be reduced to their lowestforms by repeated division by 2 or 3.Look at the section between the “2” and the “3” on theedge marked with an “8” for eighths.There are eight equally spaced lines. The lengths ofthese lines differ and indicate different fractions or partsof an inch.The longest line is in the center and is equal to 4/8 or 1/2inch.Each half-inch is divided in half by a slightly shorter lineindicating 2/8 or 1/4 on the left and 6/8 or 3/4 on the right.Each 1/4 inch is divided in half by the shortest line whichindicates 1/8 inch, and will indicate 1/8, 3/8, 5/8 and 7/8.3-1
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