ISO-255-1990.pdf

INTERNATIONAL STANDARD IS0 255 Second edition 1990-11-01 Belt drives - Pulleys for V-belts (system based on datum width) - Geometrical inspection of grooves Transmissions par courroies - Poulies B gorges pour courroies trapkoidales (systeme base sur la largeur de r - inspection of groove spacing (see clause 5); - inspection of datum diameter (see clause 6); - inspection of run-out (see clause 7). 4 Groove profile 4.1 Specification The groove profile shall be specified in the corre- sponding International Standard by the dimensions shown in figure 1 and given in table 1. -u : I Figure 1 - Groove profile Dimension Table 1 - Groove profile specification Symbol Tolerance Datum width Groove angle Groove height above datum width Groove depth below datum width wd A specified value not subject to toler- ance - the permissible tolerance on the nominal value (! for the distance between any two grooves of a single pulley. Figure 7 - Multiple groove pulley 51.2 Distance between edge of pulley and first group centre A minimum value shall be specified for the distance fbetween the outside of the rim and the axis of the first groove for all single- and multiple-groove pul- leys. A plus and minus tolerance may be assigned to the value of fin order to facilitate the alignment of the pulleys. 5.2 inspection Measure pulley groove spacing using a pulley groove tool and sets of interchangeable balls fol each individual groove section. The bail diameter shall be as specified in 6.1.2. Measure the groove spacing e, using the groove spacing locator which consists of a vernier gauge incorporating sets of interchangeable balls for each individual groove section (see figure8); the bail di- ameters are given in tableA.1. The movable ball slide shall be tightened after the bails have been properly placed in the grooves. Measure the dis- tance x using a vernier caliper or micrometer. The 3 IS0 255:1990(E) Figure 8 - Groove spacing locator measured groove spacing, e, is equal to the meas- ured dimension, X, minus the diameter of the in- spection ball used. 6 Datum diameter 6.1 Specifications 6.1.1 Datum dlameter The following dimensions shall be specified in the corresponding International Standard: - the datum diameter - nominal value dd; - the permissible tolerance on the nominal value 4; - for multiple-groove pulleys, the permissible vari- ation of the datum diameters measured in any two grooves of a single pulley. 6.1,2 Checking balls or rods The following dimensions shall be specified in the corresponding International Standard: - the diameter of bails or rods, d; - the permissible tolerance on d; - the corrective term 2h,. The diameters d shall be determined so that the simultaneous contact of the bail or the rod with the two groove sides is very closely made at the level of the datum diameter. 6.2 Inspection Use two cylindrical balls or rods of diameter d in accordance with 6.1.2. Place these two bails or rods in the groove to be checked (see figure 9). Measure the distance, K, between the planes that are ex- ternally tangent to the bails or rods and parallel to the axis of the pulley. This distance can be meas- ured using a plane and parallel assay instrument, for example a vernier caliper. The datum diameter, dd, of the groove is then given by the following relationship: dd = K - 2h, where % is the corrective term given in 6.1.2. If the pulley has several grooves, each of them shall be checked separately. IS0 255:1990(E) Figure 9 - Fitting of rods in the groove to be checked 7 Run-out tolerances 7.1 Specifications The following dimensions shall be specified in the corresponding International Standard (see figure 10): - the radial circular run-out tolerance, 1, of the outside diameter. The datum A is the axis of the bore: - the axial circular run-out tolerance, t2, measured perpendicular to the groove sidewall at the da- tum diameter. The common datum is formed by the datum A of the axis of the bore and the da- tum B of the grooved pulley face fitted to the collar of the shaft. 7.2 Inspection The radial and axial circular run-outs shall not be greater than the values specified at the measure- ment positions (see figure IO) during one revolution about the datum axis A. NOTE - The radial and axial circular run-out tolerances are shown in accordance with IS0 1101. Figure IO - Radial and axial circular run-out tolerances 5 IS0 255:1990(E) Annex A (normative) Checking balls or rods and corrective terms (see 6.1.2) for grooved pulleys complying with IS0 4183 The Inspection parameters and tolerances lacking in IS0 4183 are specified in tableA.1. Table A.1 - Checking balls or rods and corrective terms Dimensions In millimetres / Diamete;o;L balls or / “,“,“,:a”,“p Groove ,profiles Classi- tive n cal V- Narrow I I term belts V-belts nom. tot.) 2k v 55 0 -0,03 7 z SPZ 9 0 -0,036 12 A SPA 11,6 0 -0,043 15 B SPB 14,7 0 -0,043 19 C SPC 20 -4,052 26 D 28,5 0 -0,052 37 E 33,8 0 -0.082 44 1) Tolerances in accordance with IS0 286-2:1988, h9. 6 -,-,- IS0 255:1990(E) Annex B (informative) Bibliography l IS0 286-2:1988, IS0 system of limits and fits - Part 2: Tables of standard tolerance grades and limit devi- ations for holes and shafts. 2 IS0 1081:1980, Drives using V-belts and grooved pulleys - Terminology. S IS0 1101:1983, Technical drawings - Geometrical tolerancing - Tolerancing of form, orientation, location and run-out - Generalities, definitions, symbols, indications on drawings. IS0 255:1990(E) UDC 621.85.051:621.85.052.42 Descriptors: belt drives, pulleys, grooved pulleys, specifications, tests, geometrical tolerances, dimensional measurements. Price based on 7 Rams -,-,-