BS ISO 155:2019 pdf download – Belt drives — Pulleys — Limiting values for adjustment of centres
This document specifies the limiting values for the adjustment of centres of two transmission pulleys.
It is applicable to:
— crowned pulleys for flat belts;
— grooved pulleys for V-belts, either single, multiple or joined;
— grooved pulleys for V-ribbed belts;
— toothed pulleys for synchronous belts.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at
— IEC Electropedia: available at
4 Symbols
For the purpose of this document, the following symbols apply.
Symbol Definition Unit
d ± δ 1 Limits of small flat pulley diameter mm
D ± δ 2 Limits of large flat pulley diameter mm
e Groove pitch of a V-ribbed pulley mm
E Nominal centre distance mm
E – i Lower limit for the adjustment of centre distance mm
E + s Upper limit for the adjustment of centre distance mm
i 1 Factor related to the pulley dimensions and tolerances —
i 2 Factor related to belt length tolerances —
L Nominal belt length mm
s 1 is a factor related to the pulley dimensions and tolerances;
s 2 is a factor related to belt length tolerances;
s 3 is a factor related to flat pulley crowning;
s 4 is a factor related to elastic properties of the belt.
Factors with subscripts 1 to 3 determine the centre distance adjustment necessary to install a belt onto the pulleys and to readjust working tension.
Factor s 4 determines the centre distance adjustment necessary to maintain correct operation of a belt under the influence of belt extension and dimensional wear.
These limiting values should be considered by the belt manufacturers as maxima, and by the designers and makers of the machinery as minima.
6 Factors
The values of the different factors are given in the following tables:
— for factor i and factor s, see Table 1;
— for diameter tolerance for flat pulley, see Table 2;
— for datum widths for V-belts, see Table 3;
— for effective widths for joined V-belts, see Table 4;
— for Groove pitch for V-ribbed belts, see Table 5;
— for values of i 1 for synchronous belts, see Table 6;
— for values of s 4 related to belt material, see Table 7.BS ISO 155 pdf download.