DIN 21772:2012-07

For more than 50 years the parameters and deviations of cylindrical involute gears and gear pairs were defined in DIN 3960. The development of this standard indicates the constant development of the technology in this sector and is influenced by national and international knowledge. In this manner, DIN 3960 also served as a foundation for the development of an International Standard which was published as ISO 21771 "Gears - Cylindrical involute gears and gear pairs - Concepts and Geometry" in 2007. In essence, this reflects the clauses 2 and 3 "Definitions, parameters and equations for cylindrical gear teeth" and "Definitions, parameters and equations for gear pairs" from DIN 3960 of March 1987. With the intended adoption of the International Standard as DIN ISO 21771 an amendment of the total concept is necessary. The gap resulting from the intended withdrawal of DIN 3960 is filled with this standard DIN 21772. This standard specifies the terms and definitions and parameters for deviations on cylindrical involute gears, the tooth flanks of which are parts of circular involute screw surfaces. The deviation-free nominal condition is defined in ISO 21771:2006. Moreover, DIN 21772 deals with the deviations on cylindrical gear pairs in accordance with the standard ISO 21771:2006. The number adjacent to ISO 21771 symbolises the close relationship to the ISO standard which is relevant in terms of content. With the new standard numbering a mixing-up or amalgamation with the contents of DIN 3960:1987 is avoided. The following modifications have been made with respect to DIN 3960:1987: a) DIN 3960 split into DIN ISO 21771 for nominal geometry, DIN 21772 for deviations and DIN 21773 for inspection dimensions of tooth thickness; b) modified in the title: in the German version Stirnräder (involute cylindrical gears) and Stirnradpaare (involute cylindrical gear pairs) have been changed to Zylinderräder (cylindrical involute gears) and Zylinderradpaare (cylindrical gear pairs); c) text, symbols, terms, definitions and graphic representations have been revised throughout; d) the virtual number of teeth is no longer used; e) nomograms (with the exception of determination of the measuring ball diameter) are no longer included; f) flank modifications are included; g) reference ranges for flank deviations have been modified; h) the regulation of signs for tooth alignment error has been refined; i) flank surface deviations have been defined; j) base and normal pitch error have been separated; k) contact pattern has been expanded; l) the definitions in the revised version ISO 1328-1:2012 have been incorporated. Previous editions: DIN 3960:1987-03; 1980-07; 1976-10