Machinery's Handbook, 31st Edition
Transmission Roller Chains 2623 Caliper Diameter: The caliper diameter is the same as the bottom diameter for a sprocket with an even number of teeth. For a sprocket with an odd number of teeth, it is defined as the distance from the bottom of one tooth gap to that of the nearest opposite tooth gap. The caliper diameter for an even tooth sprocket is equal to pitch diameter-roller di- ameter. The caliper diameter for an odd tooth sprocket is equal to caliper factor-roller diameter. Here, the caliper factor = PD cos (90 ° ÷ N ), where PD = pitch diameter and N = number of teeth. Caliper factors for 1-in. pitch and sprockets having 9–108 teeth are given in Table 4. For other tooth numbers use above formula. Caliper diameter tolerances are minus only and are equal to . . P N 0002 + 0006 inch for the Commercial sprockets and . . P N 0001 + 0003 inch for Precision sprockets. Tolerances are given in Table 5. Table 5. Minus Tolerances on the Caliper Diameters of Precision Sprockets ANSI/ASME B29.1-2011 (R2016)
Number of Teeth
Pitch 0.250 0.375 0.500 0.625 0.750 1.000 1.250 1.500 1.750 2.000 2.250 2.500 3.000 Pitch 0.250 0.375 0.500 0.625 0.750 1.000 1.250 1.500 1.750 2.000 2.250 2.500 3.000
Up to 15
16-24 0.004 0.004 0.005 0.0055 0.006 0.007 0.008 0.009 0.010 0.011 0.012 0.013 0.015 81-99 0.005 0.006 0.0075 0.009 0.010 0.012 0.014 0.016 0.019 0.021 0.023 0.025 0.030
25-35 0.004 0.004 0.0055 0.006 0.007 0.008 0.009 0.0105 0.012 0.013 0.014 0.015 0.018
36-48 0.005 0.005 0.006 0.007 0.008 0.009 0.010 0.012 0.013 0.015 0.016 0.018 0.021
49-63 0.005 0.005 0.0065 0.008
0.004 0.004 0.004 0.005 0.005 0.006 0.007 0.007 0.008 0.009 0.010 0.010 0.012 64-80 0.005 0.006 0.007 0.009 0.010 0.011 0.013 0.015 0.017 0.019 0.021 0.023 0.027
0.009 0.010 0.012 0.013 0.015 0.017 0.018 0.020 0.024 0.006 0.007 0.009 0.011 0.013 0.015 0.018 0.021 0.024 0.027 0.030 0.033 0.039
Number of Teeth
100-120 0.006
121-143 0.006 0.007 0.0085 0.010 0.012
144 up
0.006 0.008 0.009 0.011 0.013 0.016 0.018 0.020 0.023 0.025 0.028 0.033
0.014 0.017 0.019 0.022 0.025 0.028 0.030 0.036
Minus tolerances for Commercial sprockets are twice those shown in this table. Outside Diameter: OD is the diameter over the tips of teeth. Sprocket ODs for 1-in. pitch and 9–108 teeth are given in Table 4. For other tooth numbers the OD may be determined by the following formulas in which O = approximate OD; P = pitch of chain; N = number of sprocket teeth: O = P [0.6 + cot (180 ° ÷ N )], for turned sprocket; O = pitch diameter − roller diameter + 2 × whole depth of topping hob cut, for topping hob cut sprocket.* * This dimension was added in 1984 as a desirable goal for the future. It should in no way obsolete exist- ing tools or sprockets. The whole depth WD is found from the formula: WD = ½ D r + P [0.3 − ½ tan (90 deg ÷ N a )], where N a is the intermediate number of teeth for the topping hob. For teeth range 5, N a = 5; 6, 6; 7-8, 7.47; 9-11, 9.9; 12-17, 14.07; 18-34, 23.54; 35 and over, 56.
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