C-Hook Name: gear.dll/.scr/.txt Date: July 8, 1997 Programmer: CNC Software, Inc. Description: Creates one tooth or all teeth of an involute spur or internal gear. It also computes the roll measurement for checking the gear. **************************************************************************** * NOTE: * * * * After the gear tooth/teeth is/are created, the following message * * is displayed: * * * * Maximum circular tooth thickness deviation = x.xxxxxx * * (depends on number of arcs in involute) * * * * This is not an error message. The circular tooth thickness deviation * * represents the maximum distance between the theoretical involute * * and its approximation by arcs. The deviation can be decreased by * * increasing the number of pairs of arcs in the involute. * **************************************************************************** Elements of a gear tooth: Top land An arc at the top of a spur gear or the bottom of an internal gear. Bottom land An arc at the bottom of a spur gear or the top or an internal gear. Involute curve An involute is the shape the end of a string traces as it is unwound from a cylinder. Root fillet An arc that is tangent to the bottom land and the involute curve. Top fillet An arc that is tangent to the top land and the involute curve. Flank A straight line connecting the root fillet and the involute curve. Gear parameters: Type of gear: Selects a spur (external) or internal gear. Changes the definition of circular tooth thickness. Causes the outside diameter, root diameter, fillet radius, roll diameter and roll measurement to be recomputed. Roll measurement method: The roll measurement method may be calculated on the outside or inside of the gear. Normall, the roll measurement method and gear type are the same, but they may be different if the gear is produced with an electrode. The roll diameter and roll measurement are automatically recalculated when this parameter is changed. Number of teeth The number of teeth in the gear. Causes the outside diameter, root diameter, fillet radius, roll diameter and roll measurement to be recomputed. Number of pairs of arcs in involute A larger number may be selected to reduce the error between the theoretical involute curve and its approximation. Pitch diameter The diameter at which the pressure angle and tooth thickness are measured. Causes the diametral pitch, outside diameter, root diameter, root fillet radius, roll radius and roll measurement to be recomputed. Diametral pitch This is just another way of entering the pitch diameter. The diametral pitch is equal to the number of teeth divided by the pitch diameter. Outside diameter The diameter of the top land. Root diameter The diameter of the bottom land. Pressure angle The angle between a line that is tangent to the gear and a radial line (a line passing through X0 Y0 and the intersection of the pitch circle and the gear), measured at the pitch diameter. Causes the roll measurement to be recomputed. Roll diameter The diameter of the pin used to measure the gear. Causes the roll measurement to be recomputed. Circular tooth thickness The thickness of a tooth measured along the pitch diameter. Note that different parts of the gear are measured for internal and external gears. Causes the roll measurement to be recomputed. Roll measurement a. External gear measurement The distance between the outside of the measuring pins. b. Internal gear measurement The distance between the inside of the measuring pins. Causes the tooth thickness to be recomputed. Flank angle The flank angle is defined so that it is zero if the flank is tangent to the involute. Normally, the flank angle is left at zero. Root fillet type If "Specified" is chosen, the root fillet radius will be used. If "Full" is select, the root fillet will have the largest possible radius. It will be tangent to the involute or flank, the bottom land, and the involute or flank of the adjacent gear. Root fillet radius Radius of the fillet connecting the bottom land to the involute or flank. Used only if the Root fillet type is "Specified". Tip fillet radius Radius of the fillet connecting the top land to the involute. Modifications: $lgb$ 1.0 jds 04/24/97 added number of teeth to create, diametral pitch and fillet type 1.1 jds 07/08/97 added an explanation of the circular tooth thickness deviation $lge$ Distributor: CNC Software 344 Merrow Road Tolland, CT 06084-9970 Contact: CNC Software Phone: (860) 875-5006
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