ANSI/AGMA 2003-B97, Rating the Pitting Resistance and Bending Strength of Generated Straight Bevel, Zerol Bevel, and Spiral Bevel Gear Teeth

Question 1:

ANSI/AGMA 2003-B97, clause 17 covers the method of calculating the hardness factor, C H. When a through hardened pinion is meshed with a through hardened gear and the pinion is substantially harder, the standard presents formulas that are valid in the range 1.2 ≤ HB1/HB2 ≤ 1.7.

ANSI/AGMA 2001-D04, clause 14.1 recommends using A = 0.00698 in equation 31 – which fixes CH at the value that would be calculated if HB1/HB2 = 1.7.

Question for Interpretation: What value should be used for CH when HB1/HB2 > 1.7?

AGMA’s response:

The Bevel Gearing Committee feels that the recommendation made in ANSI/AGMA 2001-D04, as noted in your comment, may also be applied in the determination of hardness ratio factor, CH, in ANSI/AGMA 2003-B97.

Question 2:

ANSI/AGMA 2003-B97, Annex C, equation C14 calculates the mean transverse gear pitch radius by taking the cosine of the pitch angle. If the pitch angle is equal to 90o, the cosine is zero and the pitch radius becomes indeterminate. If the pitch angle is greater than 90°, the pitch radius becomes negative.

There is a similar problem in AGMA 2005-D03, table 9 where the equation for the equivalent 90°ratio, m90, divides by the square root of the cosine of the pitch angle.

Question for Interpretation: What are the guidelines for the use of the standard in these situations?

AGMA’s response:

While most of ANSI/AGMA 2005-D03 (Design Manual for Bevel Gears) and ANSI/AGMA 2003-B97 applies to all bevel gears, the calculations in Annexes C and C(M) of ANSI/AGMA 2003-B97, and Tables 9 and 10 in ANSI/AGMA 2005-D03 should be limited to gears having pitch angles less than 90 degrees.

Question 3:

ANSI/AGMA 2003-B97, clause 17 covers the method of calculating the hardness factor, CH. It is assumed that the equations in this section apply to steel gearing.

Question for Interpretation: Do they apply to iron gearing? If not, what are the guidelines for CH for this material?

AGMA’s response:

The committee does not have sufficient data to present equations for the use of CH for gears made of material other than steel. Use CH = 1.0, unless experience dictates otherwise.