1.1 Rating formulas
This standard provides a method by which different
gear designs can be theoretically rated and
compared. It is not intended to assure the perfor-
mance of assembled gear drive systems.
These fundamental rating formulas are applicable
for rating the pitting resistance and bending strength
of internal and external spur and helical involute gear
teeth operating on parallel axes. The formulas
evaluate gear tooth capacity as influenced by the
major factors which affect gear tooth pitting and gear
tooth fracture at the fillet radius.
The knowledge and judgment required to evaluate
the various rating factors come from years of
accumulated experience in designing, manufactur-
ing, and operating gear units. Empirical factors
given in this standard are general in nature. AGMA
application standards may use other empirical
factors that are more closely suited to the particular
field of application. This standard is intended for use
by the experienced gear designer, capable of
selecting reasonable values for the factors. It is not
intended for use by the engineering public at large.
1.2 Exceptions
The formulas of this standard are not applicable to
other types of gear tooth deterioration such as plastic
yielding, wear, case crushing and welding. They are
also not applicable when vibratory conditions ex-
ceed the limits specified for the normal operation of
the gears (see ANSI/AGMA 6000-A88, Specifica-
tion for Measurement of Lateral Vibration on Gear
Units).
The formulas of this standard are not applicable
when any of the following conditions exist:
- Damaged gear teeth.
- Spur gears with transverse contact ratio, rap,
less than 1.0.
- Spur or helical gears with transverse contact
ratio, mp greater than 2.0.
- Interference exists between tips of teeth and
root fillets.
- Teeth are pointed.
- Backlash is zero.
- Undercut exists in an area abovethetheoreti-
cai start of active profile. The effect of this under-
cut is to move the highest point of single tooth
contact, negating the assumption of this calcula-
tion method. However, the reduction in tooth root
thickness due to protuberance below the active
profile is handled correctly by this method.
- The root profiles are stepped or irregular. The
,/factor calculation uses the stress correction fac-
tors developed by Dolan and Broghamer [19].
These factors may not be valid for root forms
which are not smooth curves. For root profiles
which are stepped or irregular, other stress
correction factors may be more appropriate.
- Where root fillets of the gear teeth are pro-
duced by a process other than generating.
- The helix angle atthe standard (reference) di-
ameter* is greater than 50 degrees.
Scuffing criteria are not included in this standard. A
method to evaluate scuffing risk can be found in
AGMA 925-A03. This information is provided for evaluation by users of this standard, with the intent to
include a scuffing evaluation method in a future
version of this standard.
Design considerations to prevent fractures emanat-
lng from stress risers on the tooth profile, tip
chipping, and failures of the gear blank through the
web or hub should be analyzed by general machine
design methods.
AGMA 2001-D04-2004 history
2004AGMA 2001-D04-2004 Fundamental Rating Factors and Calculation Methods for Involute Spur and Helical Gear Teeth