ANSI/AGMA 6002-B93 pdf free.American National Standard Design Guide for Vehicle Spur and Helical Gears.
For external gears with web section, the minimum rim thickness under the tooth root should be on the order of 75 percent of the whole depth of the tooth.Any extemal or intemal gear of the webless type should have a minimum thickness under the tooth root equal to the whole depth of the tooth. Heat treatment distortion and rim failure from stresses should be taken into consideration when designing rim thickness.
2.8 Heat treat variation
The rim and web design shape has a proiound infiurence on the distortion of the gear. Vehicle gears in the highly loaded class may be subjected to heat treat temperatures in excess of 1700°F (927°C). It is therefore recommended that the gear rim and web be proportionedto permit the most uniform rate of heat removal from the surface of the blank.
2.9 Involute profile modifications
A profle modification is used to minimize the detrimental effects of tooth deflections, rimbending,assembly tolerances andtooth variations. Theoretically, the amount of profile modification coresponds to the deflections encountered under only one set of operating conditions. Therefore, when gears with modified profiles operate at anycondition other than at the design point, some effect in action is introduced. Over- -modification may cause an increase inthe surface compressive stress, thereby increasing the ptting tendency.
2.9.1 Typical modifications
Table 2 shows profile moodfications which are required on larger and more heavily loaded teethto compensate for deflections under load and reduce premature failure. These values may be llocated as tip or flank modifications on one or both gears in mesh.
2.9.2 Drawing specifications
Figure 2 shows the recommended way of defining profile modification showing 0.0002 to 0.0007 in (0.005 to 0.018 mm) tip and 0.0003 to 0.0008 in (0.007 to 0.020 mm) flank relief. Reference ANSV AGMA 2000- A88.
2.10 Lead crowning (tooth alignment)
In some cases, it is not possible to hold a fixed shaft alignment. Variations in tolerances or deflections of the supporting structure may tend to concentrate the load on one end of the tooth. A tooth with a slight crown (ends thinner than the middle of the tooth) may be used to ffset such a condition.
Vehicle gears very often require crowning to avoid concentrations of loads at the ends of the teeth. In some cases, particularly with overhung parts, the crowning may be off center or may be different on opposite sides of the teeth.ANSI/AGMA 6002 pdf free download.