In order to improve the tooth form of roll-finished involute helical gears, roll-finishing by a die-wheel with longitudinal tooth form correction, i.e. crowning, was investigated. The simulated and ...the measured results indicate that the use of a crowned die-wheel enables roll-finishing under lower applied loading than the use of a die-wheel without correction, and brings a high tooth form accuracy. Even in case of roll-finishing of work-gears with large face width, a fairly good tooth form over a whole tooth flank can be also obtained by using the crowned die-wheel, if the condition of axial feed of work-gear is selected properly in consideration of the amount of crowning correction of die-wheel.
The variation of the maximum bending stress and the average maximum contact pressure of helical gear sets with unequal and offset face widths are investigated. Eight cases of design of a helical gear ...set with different face widths and offset values always having the same effective contact face width are studied. These eight cases of design summarize a total of 28 different combinations of the direction of the offset, the hand of helix, and the direction of rotation of the pinion. Stress analysis is performed for 21 contact positions distributed uniformly over two angular pitches of rotation of the pinion. The results show that for a preestablished direction of the extra face width for one of the gears and without front and back end reliefs, the maximum bending stress can be reduced up to 6.94% but the average contact pressure may increase as much as 35.15%. However, if front and back end reliefs are applied, the maximum bending stress can be reduced by 5.53% and the average contact pressure reduced by 4.79%. In general, designs considering unequal and offset face widths with adequate front and back end reliefs as well as appropriate tip reliefs can improve the mechanical behavior of helical gear sets.
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