720 Lengths of Chords Table 3. Lengths of Chords for Spacing Off the Circumferences of Circles with a Diameter Equal to 1 (English or Metric units) No. of Spaces Length of Chord No. of Spaces Length of Chord No. of Spaces Length of Chord No. of Spaces Length of Chord 3 0.866025 41 0.076549 79 0.039757 117 0.026848 4 0.707107 42 0.074730 80 0.039260 118 0.026621 5 0.587785 43 0.072995 81 0.038775 119 0.026397 6 0.500000 44 0.071339 82 0.038303 120 0.026177 7 0.433884 45 0.069756 83 0.037841 121 0.025961 8 0.382683 46 0.068242 84 0.037391 122 0.025748 9 0.342020 47 0.066793 85 0.036951 123 0.025539 10 0.309017 48 0.065403 86 0.036522 124 0.025333 11 0.281733 49 0.064070 87 0.036102 125 0.025130 12 0.258819 50 0.062791 88 0.035692 126 0.024931 13 0.239316 51 0.061561 89 0.035291 127 0.024734 14 0.222521 52 0.060378 90 0.034899 128 0.024541 15 0.207912 53 0.059241 91 0.034516 129 0.024351 16 0.195090 54 0.058145 92 0.034141 130 0.024164 17 0.183750 55 0.057089 93 0.033774 131 0.023979 18 0.173648 56 0.056070 94 0.033415 132 0.023798 19 0.164595 57 0.055088 95 0.033063 133 0.023619 20 0.156434 58 0.054139 96 0.032719 134 0.023443 21 0.149042 59 0.053222 97 0.032382 135 0.023269 22 0.142315 60 0.052336 98 0.032052 136 0.023098 23 0.136167 61 0.051479 99 0.031728 137 0.022929 24 0.130526 62 0.050649 100 0.031411 138 0.022763 25 0.125333 63 0.049846 101 0.031100 139 0.022599 26 0.120537 64 0.049068 102 0.030795 140 0.022438 27 0.116093 65 0.048313 103 0.030496 141 0.022279 28 0.111964 66 0.047582 104 0.030203 142 0.022122 29 0.108119 67 0.046872 105 0.029915 143 0.021967 30 0.104528 68 0.046183 106 0.029633 144 0.021815 31 0.101168 69 0.045515 107 0.029356 145 0.021664 32 0.098017 70 0.044865 108 0.029085 146 0.021516 33 0.095056 71 0.044233 109 0.028818 147 0.021370 34 0.092268 72 0.043619 110 0.028556 148 0.021225 35 0.089639 73 0.043022 111 0.028299 149 0.021083 36 0.087156 74 0.042441 112 0.028046 150 0.020942 37 0.084806 75 0.041876 113 0.027798 151 0.020804 38 0.082579 76 0.041325 114 0.027554 152 0.020667 39 0.080467 77 0.040789 115 0.027315 153 0.020532 40 0.078459 78 0.040266 116 0.027079 154 0.020399 For circles of other diameters, multiply length given in table by diameter of circle. Example: In a drill jig, 8 holes, each 1 ⁄ 2 inch diameter, were spaced evenly on a 6-inch diameter circle. To test the accuracy of the jig, plugs were placed in adjacent holes, and the distance over the plugs was measured with a micrometer. What should be the micrometer reading? Solution: The micrometer reading equals the diameter of one plug plus 6 times the chordal distance between adjacent hole centers given in the table above. Thus, the reading should be 1 ⁄ 2 + (6 3 0.382683) = 2.796098 inches. Machinery's Handbook, 31st Edition
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