Module System Gearing Rules for Module System of Gearing Machinery's Handbook, 31st Edition
2298
To Find
Rule
Rule 1: To find the metric module, divide the pitch diameter in millimeters by the number of teeth. Example 1: The pitch diameter of a gear is 200 millimeters and the number of teeth, 40; then 40 200 5 Module = = Rule 2: Multiply circular pitch in millimeters by 0.3183. Example 2: (Same as Example 1. Circular pitch of this gear equals 15.708 millimeters.) . . 15 708 0 3183 5 Module # = = Rule 3: Divide outside diameter in millimeters by the number of teeth plus 2. Note: The module system is usually applied when gear dimensions are expressed in millimeters, but module may also be based on inch measurements. Rule: To find the English module, divide pitch diameter in inches by the number of teeth. Example: A gear has 48 teeth and a pitch diameter of 12 inches. Rule: To find the metric module equivalent to a given diametral pitch, divide 25.4 by the diametral pitch. Example: Determine metric module equivalent to 10 diametral pitch. . . 10 254 254 Equivalent module = = Note: The nearest standard module is 2.5. Rule: To find the diametral pitch equivalent to a given module, divide 25.4 by the module. (25.4 = number of millimeters per inch.) Example: The module is 12; determine equivalent diametral pitch. . . 12 254 2117 Equivalent diametral pitch = = Note: A diametral pitch of 2 is the nearest standard equivalent. 48 12 4 1 Module module or 4 diametral pitch = = Rule: Multiply number of teeth by module. Example: The metric module is 8 and the gear has 40 teeth; then . D 40 8 320 12598 millimeters inches # = = =
Metric Module
English Module
Metric Module Equivalent to Diametral Pitch
Diametral Pitch Equivalent to Metric Module
Pitch Diameter
Outside Diameter Rule: Add 2 to the number of teeth and multiply sum by the module. Example: A gear has 40 teeth and module is 6. Find outside or blank diameter. 40 2 6 252 Outside diameter millimeters # = + = ^ h For tooth dimensions, see table Tooth Dimensions Based Upon Module System ; also formulas in German Standard Tooth Form for Spur and Bevel Gears DIN 867 .
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