Overview
EN ISO 887:2000 (ISO 887:2000) - "Plain washers for metric bolts, screws and nuts for general purposes - General plan" - defines the general dimensional system and preferred combinations for plain (flat) washers used with metric fasteners. Published by ISO (Technical Committee ISO/TC 2 - Fasteners) and adopted as a CEN/EN national standard, it covers nominal thread diameters from 1 mm to 150 mm and describes product grades A and C. The standard is a general plan: it establishes ranges of clearance holes, outside diameters, thicknesses and preferred dimension combinations, and refers to separate product standards for detailed series and forms.
Key topics and technical requirements
- Scope: Full range of nominal dimensions for plain washers for general-purpose bolts, screws and nuts (1 mm to 150 mm). Not intended for screw-and-washer assembly hole/thickness design.
- Clearance holes: Clearance hole diameters are selected in accordance with ISO 273 (fine series for smaller sizes and thin washers, medium series for larger or thicker washers); note ISO 273 tolerances are for information only - actual washer tolerances are specified elsewhere.
- Outside diameters: A defined set of outside diameter values (see Table 1 in the standard) provides consistent selection across size ranges.
- Thicknesses: Nominal thickness options are given (examples include 0.3, 0.5, 0.8, 1, 1.2, 1.6, 2, etc., up to larger values shown in the standard tables).
- Preferred combinations: Table 3 lists preferred nominal combinations of inner diameter, outside diameter and thickness, grouped into small, normal, large and extra-large series and mapped to product grades A and C.
- Tolerances: Dimensional tolerances for plain washers are specified by ISO 4759-3.
- Guidance: Annex A (informative) provides guidance on matching washers to bolts, screws and nuts by hardness classes and product grades; it also references application-specific considerations.
Applications and users
EN ISO 887 is intended for:
- Fastener manufacturers and tooling suppliers establishing product ranges and catalogs.
- Mechanical designers and engineers specifying washers for machinery, automotive, construction and general engineering.
- Procurement and quality engineers who verify conformity to dimensional and tolerance requirements.
- Standards committees and testing laboratories referencing baseline washer dimensions and preferred combinations.
Practical benefits include standardized interchangeability, simplified procurement, and clearer design rules for washer selection with metric bolts and nuts.
Related standards
- ISO 273 - Clearance holes for bolts and screws
- ISO 4759-3 - Tolerances for plain washers (product grades A and C)
- ISO 7089 / 7090 / 7091 / 7092 / 7093-1 / 7093-2 / 7094 - Product standards for plain washers (normal, chamfered, small, large, extra large series)
