Gear teeth involute profile

Teeth have an involute profile, a curve that is generated by the rolhng of a straight line over a circle, as shown in Fig. 29-83. Although many cui ves could be used for gear teeth, the involute is the preferred one because it allows the correc t engagement, even when the distance between the centers of the gears is not accurately held. 

In conventional involute profile gear teeth the entrainment of lubricant occurs across the direction of surface finish. In principle the techniques of micro ehl analysis described here can be applied to this configuration, but account must be taken of the non-steady nature of the situation. 

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