b = Dedendum
c = Clearance
hk = Working Depth
ht = Whole Depth
Pc = Circular Pitch
rf = Fillet Radius
t = circular Tooth Thickness
f = Pressure Angle
Figure 1.6 Extract from AGMA 201.02 (ANSI B6.1 1968)
3.0 GEAR TOOTH FORMS AND STANDARDS
involute gear tooth forms and standard tooth
proportions are specified in terms of a basic rack which has straight-sided teeth for
involute systems. The American National Standards Institute (ANSI) and the American Gear
Manufacturers Association (AGMA) have jointly established standards for the USA. Although
a large number of tooth proportions and pressure angle standards have been formulated,
only a few are currently active and widely used. Symbols for the basic rack are given in
Figure 1.6 and pertinent standards for tooth proportions in Table 1.1.
Note that data in Table 1.1 is based upon diametral pitch
equal to one. To convert to another pitch divide by diametral pitch.
3.1 Preferred Pitches
Although there are no standards for pitch choice a preference has developed among gear designers and producers. This is given in Table 1.2. Adherence to these pitches is very common in the fine- pitch range but less so among the coarse pitches.
3.2 Design Tables
For the preferred pitches it is helpful in gear design to have basic data available as a function of the number of teeth on each gear, Table 1.3 lists tooth proportions common to a given diametral pitch, as well as the diameter of a measuring wire. Table 1.6 lists pitch diameters and the over-wires measurement as a function of tooth number (which ranges from 18 to 218) and various diametral pitches, including most of the preferred fine pitches. Both tables are for 20° pressure-angle gears.
3.3 AGMA Standards
In the United States most gear standards have been developed and sponsored by the AGMA. They range from general and basic standards, such as those already mentioned for tooth form, to specialized standards. The list is very long and only a selected few, most pertinent to fine pitch gearing, are listed in Table 1.4. These and additional standards can be procured from the AGMA by contacting the headquarters office at 1500 King Street; Suite 201; Alexandria, VA 22314 (Phone: 703-684-0211).
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a = Addendum b = Dedendum c = Clearance hk = Working Depth ht = Whole Depth Pc = Circular Pitch rf = Fillet Radius t = circular Tooth Thickness f = Pressure Angle |
Figure 1.6 Extract from AGMA 201.02 (ANSI B6.1 1968) |
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