BS ISO 9981:2020 pdf free.Belt drives – Pulleys and V-ribbed belts for the automotive industry一PK profile: Dimensions.
BS ISO 9981 This document specifies the principal dimensional characteristics of V-ribbed pulley groove profiles, together with the corresponding endless V-ribbed belts of PK profile which are used predominantly for automotive accessory drive applications.  This document does not apply to the complete array of V-ribbed belts and pulleys of PH, P], PK, PL and PM profile for industrial and other non-automotive applications which are covered by ISO 9982. PK belt profile dimensions and tolerances are the same in both International Standards. 6.2 and 6.3 of this document do not apply to elastic belts. There are no normative references in this document. No terms and definitions are listed in this document. ISO and IEC maintain terminological databases for use in standardization at the following addresses:  一ISO Online browsing platform: available at https://www.iso.org/obp 一IEC Electropedia: available at http://www.electropedia.org/ 5.3.2 Groove-to-groove diameter tolerances The variation in diameters between the grooves in any one pulley shall not exceed 0,15 mm. This variation is obtained by comparing the diameters over balls or rods. 5.3.3 Radial and axial circular run-out Radial and axial circular run-outs shall not exceed 0,25 mm full indicator movement (FIM). Run-out in the two directions is measured separately with a ball mounted under spring pressure to ensure contact with the groove as the pulley is rotated. 5.3.4 Diameter over balls The tolerances on the diameters over balls, K, shall not exceed +0,6 mm. 5.3.5 Groove finish The pulley grooves shall have a surface roughness Ra≤3,2 μm. See ISO 254 and ISO 4287 for definitions and the method of measurement. 5.4 Pitch diameter, dp The fit of a V-ribbed belt in the corresponding pulley is shown in Figure 3. The true pitch diameter of a V-ribbed pulley is slightly larger than the effective diameter and its exact value is determined with the particular belt being used. A nominal value of the effective line differential, be, of 2 mm may be used to calculate the speed ratio. If more precision is required, the belt manufacturer should be consulted. Further information is given in the ISO 8370 series.BS ISO 9981 pdf download.