Overview
SIST ISO 355:2020 - Rolling bearings - Tapered roller bearings - Boundary dimensions and series designations - is the third edition (2019) international standard that defines the nominal boundary dimensions and series coding for complete single‑row and double‑row tapered roller bearings. It also specifies flange dimensions for a selection of tapered roller bearings with flanged outer rings and establishes a standardized series designation system used to build bearing designations.
This edition cancels and replaces ISO 355:2007 and incorporates technical revisions including added contact‑angle and chamfer data for double‑row bearings and complete tables for bearings with flanged outer rings.
Key topics and technical requirements
- Boundary dimensions: Detailed nominal dimensions for single‑row and double‑row tapered roller bearings (see Tables 4–16 in the standard), including bore (d), outside diameter (D), widths (T, B, C), flange height (h), chamfer dimensions (r), contact angle (α) and related envelope dimensions.
- Series designations: A three‑symbol system (example: 2AC) covering:
- first symbol - contact angle series (angle ranges),
- second symbol - diameter series (D/d relationship ranges),
- third symbol - width series (width/height relationship ranges).
- Flanged outer rings: Flange geometry for specified sizes; additional flange dimensions provided in Annex A.
- Normative references and symbols: Uses ISO 492 for GPS and tolerances, ISO 582 for maximum chamfer values, ISO 1132‑1 and ISO 5593 for terms, and ISO 15241 for symbols.
- Tables and figures: Comprehensive dimension tables grouped by contact‑angle series and diagrams for single‑row, double‑row, matched pairs and flanged outer ring variants.
- Tolerancing and chamfers: Tolerances are those listed in ISO 492; chamfer maximums per ISO 582. Front face chamfers are not tabulated but front corners shall not be sharp.
Practical applications - Who uses SIST ISO 355:2020
- Bearing manufacturers - for standardized part geometry, production tooling and interchangeability.
- Machine and gearbox designers (OEMs) - to select correct tapered roller bearing sizes, flanged outer rings and to ensure assembly envelope compatibility.
- Procurement and specification writers - to reference unambiguous bearing series designations in purchase orders and technical specifications.
- Quality, testing and maintenance teams - for inspection limits, replacement compatibility and maintenance planning.
- Standards writers and component libraries - to align CAD libraries, bills of materials and part number systems with international practice.
Related standards
- ISO 492 - Rolling bearings - Radial bearings - GPS and tolerance values
- ISO 582 - Rolling bearings - Chamfer dimensions - Maximum values
- ISO 10317 - Bearing designation system (used in combination with ISO 355 series codes)
- ISO 1132‑1, ISO 5593, ISO 15241 - Terminology and symbols for rolling bearings
SIST ISO 355:2020 is essential for anyone specifying, manufacturing or engineering with tapered roller bearings to ensure dimensional interchangeability, clear series coding and correct flange geometry. Keywords: ISO 355, tapered roller bearings, boundary dimensions, series designations, flanged outer rings, bearing standards.