ISO 3548 pdf download.Plain bearings — Thin-walled half bearings with or without flange — Tolerances, design features and methods of test
1 Scope
This International Standard specifies tolerances, design features and test methods for thin-walled half bearings with integral flange up to an outside diameter of D o of 250 mm and without flange up to an outside diameter of D o of 500 mm. Due to the variety of design it is, however, not possible to standardize the dimensions of the half bearings. Half bearings according to this International Standard are predominantly used in reciprocating machinery and consist of a steel backing and one or more bearing metal layers on the inside. In reciprocating machinery, flanged half bearings may be used in connection with half bearings without flange. Alternatively to serve as a flanged half bearing, it is possible to use a half bearing without flange together with two separate half thrust washers in accordance with ISO 6526; or a half bearing with assembled flanges. NOTE All dimensions and tolerances are given in millimetres.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 4288, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Rules and procedures for the assessment of surface texture . ISO 6524, Plain bearings — Thin-walled half bearings — Checking of peripheral length . ISO 6526, Plain bearings — Pressed bimetallic half thrust washers — Features and tolerances .
3 Symbols
See Figures 1 and 2 and Table 1 .
4 Dimensions and tolerances
4.1 Housing diameter, half bearing outside diameter and nip The housing diameter shall be manufactured to tolerance class H6. Thereby the half bearing outside diameter shall be selected with such an oversize that an adequate interference fit is ensured in the housing diameter. In the case of housings made from materials having a high coefficient of expansion or where other factors such as housing dimensional stability are involved, the housing size may depart from tolerance class H6 but shall always be produced in accordance with a grade 6 tolerance. The half bearing in a free state is flexible so that its outside diameter cannot be measured directly. Instead of this, its peripheral length is determined by means of special checking fixtures. The peripheral length results from the periphery of the checking block bore and the nip taking into account the reduction under a given checking load per joint face (see clause 6). For the calculation of the effective interference fit of the half bearings in the housing, see [5] . The tolerances given in Table 2 for the nip, apply to half bearings with machined joint faces. Different materials and housing design require different interference fits, therefore tolerances only are given in Table 2.4.2 Half bearing wall thickness and bearing bore Nominal dimensions to be preferred for the wall thickness of the bearing are given in Table 2. Particulars of the wall thickness for each application cannot be specified in general, therefore only tolerances can be given for the wall thickness. These tolerances and the surface roughnesses of the bearing back and the sliding surface of half bearings with or without electroplated antifriction layers are given in Table 2. The tolerance for the half bearing wall thickness depends on whether the bearing bore is subject to a final machining operation (i.e. “as-machined”) or whether the bearing bore is electroplated without further machining (i.e. “as-plated”). Slight surface deformations are acceptable on the outside diameter of the bearing provided that they are not numerous. However, the measurement of the wall thickness shall not be carried out in these areas.