Related Resources: gears

AGMA Major Metallurgical Factors

Gear Engineering and Design

AGMA Major metallurgical factors affecting the allowable contact stress number, sac, and allowable bending stress number, sat, of flame or induction hardened steel gears1, 2, 3

Metallurgical factor
Grade 1
Grade 2
ASTM E112 grain size
Predominantly 5 or finer
Predominantly 5 or finer
Material composition
Not specified
Medium carbon alloy steel
Prior structure
Not specified
Quenched and tempered
Material form
Not specified
Forgings and wrought steel; castings with magnetic particle inspection of gear tooth area
Not specified
AMS 2301 or ASTM A866 for wrought steel (certification not required); cast-ings are permissible with primarily round (Type 1) sulfide inclusions.
Sulfur content
Not specified
0.025% maximum for wrought
0.040% maximum for castings
Core hardness, center of tooth at root diameter, sac only
Not specified
28 HRC minimum
Core hardness, center of tooth at root diameter, sat only
Not specified
Type A - 28 HRC minimum
Type B - not specified
Non-martensitic transformation products in hardened zone
Limited by effect on specified hardness
10% maximum, no free ferrite
Surface hardness, sac only
Surface hardness at root, sat only
Type A -50 HRC min
Type B - not specified
Type A -54 HRC min
Type B - not specified
Hardness pattern, sat only
As required per table 4
ANSI/AGMA Standard D04
Type A Contour pattern with a ductile core
Type B not specified
Magnetic particle (method per ASTM E709 on teeth)5
Not specified Not specified
Pitch Pnd
Maximum indication,
≤ 3
>3 to <10


1) Criteria for grades 1 & 2 apply to both stress numbers unless otherwise specified in the metallurgical factor column.
2) All criteria in any given grade must be met to qualify for the stress number in that grade.
3) Unless otherwise specified, proper process control with periodic verification is an acceptable method to meet these requirements.
4) The grade cleanliness requirements apply only to those portions of the gear material where the teeth will be located to a distance below the finished tip diameter of at least two times the tooth depth. On external gears, this portion of the gear blank normally will be less than 25 percent of the radius.
5) No cracks, bursts, seams or laps are permitted in the tooth area of finished gears, regardless of grade. Limits: maximum of one indication per inch of face width and maximum of five in one tooth flank. No indications allowed below 1/2 working depth of tooth. Indications smaller than 1/64 inch are not considered. Removal of defects which exceed the stated limits is acceptable provided the integrity of the gear is not compromised.



  • ANSI/AGMA American National Standards Institutue. American Gear Manufacturers Association Specification AGMA 201-D04