Request for Interpretation for ANSI/AGMA 6135-A02, Design, Rating and Application of Industrial Globoidal Wormgearing (Metric Edition)
Issued November 1, 2016
Question/statement:
The current rating standards for wormgears [6034, 6035, & 6135] do not include allowable stress numbers for the gear materials now being used in these products. Can the committee responsible for these standards offer any guidance on what allowable stress numbers should be used for these materials?ย For more details on the question, see Attachment A.
AGMA response:
At this time AGMA has no recommendation on ratings procedures for worm gearing using Cast and Ductile Iron.ย The Worm Gear Rating Committee has recently discussed this subject in regard to the current revision process for AGMA 6034. It was decided that not enough data is currently available to include these materials.ย
Furthermore, the information presented at the web address, provided by the questioner, relative to Cast Iron used for the worm gear material, is extracted from the British Standard BS721.ย This standard does place a limit on the sliding velocity being less than 500 ft/min.ย
Additionally, the questioner should be informed of the proposed cautionary note below currently being considered for inclusion in the next revision of AGMA 6034.
“The rating method described by this standard does not apply to worm wheels made of ductile iron; although such materials are commonly used in worm gearing.ย Ductile iron can present additional challenges for the gear designer which are not covered by this standard including increased risks for fretting with the steel worm when vibration is present.”