Specification summary of DIN 988 as applied to shim rings (support washers): the dimensions the standard fixes, the full size range supplied, and the related designations commonly cross-referenced.
DIN 988 — Scope
DIN 988 specifies the dimensional requirements for shim rings (support washers). Material, surface condition and any performance rating are set by separate documents specific to this part family — ISO 898-1 and ISO 898-2, which govern bolt and nut property classes, do not apply here.
Tolerance & Product Grades
Tolerances for shim rings (support washers) are given as limits on the individual dimensions in the table rather than as a fastener product grade. Where a general-tolerance class is cited on the drawing instead, it applies to the dimensions not otherwise toleranced.
Dimensions Specified by DIN 988
| Size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness s (mm) | Reference standard | Notes |
|---|---|---|---|---|---|
| 3 | 3 | 6 | 0.1 | DIN 988 | Also 0.15, 0.2 thickness |
| 4 | 4 | 8 | 0.1 | DIN 988 | Also 0.15, 0.2, 0.3 thickness |
| 5 | 5 | 10 | 0.1 | DIN 988 | Also 0.15, 0.2, 0.3 thickness |
| 6 | 6 | 12 | 0.1 | DIN 988 | Also 0.15, 0.2, 0.3, 0.5, 1, 1.2 thickness |
| 7 | 7 | 13 | 0.1 | DIN 988 | Also 0.15, 0.2, 0.3, 0.5, 1, 1.2, 1.4 thickness |
| 8 | 8 | 14 | 0.1 | DIN 988 | Also 0.15, 0.2, 0.3, 0.5, 1, 1.2, 1.5 thickness |
| 9 | 9 | 15 | 0.1 | DIN 988 | Thickness range 0.1-1.6 |
| 10 | 10 | 16 | 0.1 | DIN 988 | Thickness range 0.1-1.8 |
| 11 | 11 | 17 | 0.1 | DIN 988 | Thickness range 0.1-1.8 |
| 12 | 12 | 18 | 0.1 | DIN 988 | Thickness range 0.1-1.8 |
Equivalent Standards
Where direct equivalents exist (ISO ↔ DIN, ISO ↔ ASME), they are listed on the parent Shim Rings (Support Washers) page. Always confirm against the dimensions on this page, since some "equivalent" standards differ in tolerances and head geometry.
Companion Standards
DIN 988 controls only the geometry of shim rings (support washers). Surface finish is governed by separate finish standards (for example ISO 4042 for electroplating), and corrosion testing by ISO 9227 (neutral salt spray). Mechanical performance is set by the standards specific to this part family, not by ISO 898-1 or ISO 898-2, which apply to bolts, screws and nuts.
