Overview
ISO 3547-7:2020 - "Plain bearings - Wrapped bushes - Part 7: Measurement of wall thickness of thin-walled bushes" specifies checking methods and measuring equipment for determining the total wall thickness of finished thin-walled wrapped bushes. Prepared in accordance with ISO 12301, this standard defines measurement principles, measuring-line and point schemes, and equipment requirements (all dimensions in millimetres). Its primary purpose is to verify wall thickness and tolerances in support of ISO 3547-1 dimensional requirements.
Key topics and requirements
- Measuring principle
- Gauging axis must be radial and perpendicular to the outside surface to locate the minimum wall thickness.
- Measurements may be recorded as a single (direct) or sum measurement (contact or non-contact gauges).
- Line measurement (circumferential)
- Continuous wall-thickness measurement around the circumference at specified measuring lines (positions depend on bearing width B and lateral limit C).
- Number and position of measuring lines follow the rules in the standard (see Table 2 / Figure 3); special cases (grooves, holes, markings) require supplier/customer agreement.
- Point measurement
- Point-by-point schemes (three- or six-point) apply for B ≤ 90 mm and outside diameter D ≤ 150 mm. Larger parts require agreement between supplier and user.
- Measuring-pin geometry
- Outside-surface pin radius: 1.5 mm ± 0.2 mm.
- Inside-surface pin radius: specified by bush outside diameter and material:
- D ≤ 10 mm: 1.5 ± 0.2 mm
- 10 < D ≤ 25 mm: 3 ± 0.2 mm
- 25 < D ≤ 150 mm: metallic bushes 3 ± 0.2 mm, polymer bushes 5 ± 0.2 mm
- D > 150 mm: 5 ± 0.2 mm
- Measuring pin load
- Applied load Fpin on the sliding layer: 0.8 N to 2.5 N (per ISO 12301).
- Equipment verification
- Measurement uncertainty checks at user-determined frequencies; limits to comply with industry requirements.
Applications and users
- Practical uses:
- Production quality control of wrapped bushes and thin-walled plain bearings
- Incoming inspection and supplier acceptance testing
- Metrology procedure design and calibration of gauges for bush wall thickness
- Resolving non-conformities from manufacturing deformations or markings
- Typical users:
- Bearing manufacturers and suppliers
- Quality assurance and inspection labs
- Mechanical/metrology engineers and test technicians
- OEMs specifying bearing acceptance criteria
Related standards
- ISO 3547-1 - Plain bearings - Wrapped bushes - Part 1: Dimensions (tolerances and designation)
- ISO 12301 - Quality control techniques and inspection of geometrical and material quality characteristics
- ISO 3547-2 - Test data for outside and inside diameters
Keywords: ISO 3547-7:2020, plain bearings, wrapped bushes, wall thickness measurement, thin-walled bushes, measuring pin radius, measuring pin load, ISO 12301, line measurement, point measurement.