What Is ISO 7089?
The international standard for plain washers that distribute clamping force and protect assembled surfaces under bolted joints.
ISO 7089 specifies the characteristics of plain washers, normal series, Product Grade A, for general-purpose use with metric bolts, screws, and nuts. These washers sit under the bolt head or nut to distribute the clamping load over a larger surface area, preventing damage to the assembled parts and reducing the risk of loosening.
Tight Tolerances
ISO 7089 is Product Grade A, meaning tighter dimensional tolerances on inner diameter, outer diameter, and thickness. Ensures consistent fit and load distribution in precision assemblies.
Standard Load Distribution
The normal series provides the standard outer diameter-to-inner diameter ratio for general bolting. For larger bearing surfaces, specify ISO 7093 (large series) or ISO 7094 (extra large series).
Standard Specifications
Size Range & Dimensions
- Nominal size range: M1.6 up to and including M64
- Inner diameter (d1): Slightly larger than nominal bolt diameter to ensure clearance
- Outer diameter (d2): Standard bearing surface for normal series
- Thickness (h): Varies by size — thicker washers for larger bolts
- Product Grade A: Tighter tolerances on all dimensions
Materials & Hardness Classes
- Steel Washers — 200 HV: For use under property class ≤ 8.8 bolts and nuts. General-purpose, economical.
- Steel Washers — 300 HV: For use under property class 8.8 to 10.9 bolts and nuts. Hardened to prevent embedding under high preload.
- Stainless Steel: A2 (SS 304) and A4 (SS 316) for corrosive environments. Supplied in annealed condition.
- Non-Ferrous Metals: Brass, copper, and aluminum washers available for electrical, thermal, or chemical compatibility.
- Coatings: Zinc plated, hot-dip galvanized, and plain (oiled) finishes available for steel washers.
ISO 7089 vs DIN 125 — Key Differences
ISO 7089 and DIN 125-A are largely interchangeable for most sizes, but there are differences in how standards are referenced and some dimensional tolerances:
| Feature | DIN 125-A | ISO 7089 |
|---|---|---|
| Standard Origin | German (legacy) | International (active) |
| Product Grade | Grade A (tight) | Product Grade A |
| Chamfer | No chamfer (square edge) | No chamfer (square edge) |
| Chamfered Variant | DIN 125-B | ISO 7090 |
| Size Range | M1.6 – M64 | M1.6 – M64 |
| Thickness Tolerance | DIN 267 | ISO 4759-1 |
For chamfered plain washers (one side beveled to clear bolt fillet radius), specify ISO 7090 (replaces DIN 125-B) instead of ISO 7089.
ISO 7089 Key Dimensions
Dimensions in millimetres for common sizes. d1 = Inner Diameter, d2 = Outer Diameter, h = Thickness.
| Size | d1 (min) | d1 (max) | d2 (max) | h (nom) | h (min) | h (max) |
|---|---|---|---|---|---|---|
| M5 | 5.3 | 5.48 | 10.0 | 1.0 | 0.8 | 1.2 |
| M6 | 6.4 | 6.62 | 12.0 | 1.6 | 1.3 | 1.9 |
| M8 | 8.4 | 8.62 | 16.0 | 1.6 | 1.3 | 1.9 |
| M10 | 10.5 | 10.77 | 20.0 | 2.0 | 1.7 | 2.3 |
| M12 | 13.0 | 13.27 | 24.0 | 2.5 | 2.2 | 2.8 |
| M16 | 17.0 | 17.27 | 30.0 | 3.0 | 2.7 | 3.3 |
| M20 | 21.0 | 21.33 | 37.0 | 3.0 | 2.7 | 3.3 |
| M24 | 25.0 | 25.33 | 44.0 | 4.0 | 3.7 | 4.3 |
| M30 | 31.0 | 31.39 | 56.0 | 4.0 | 3.7 | 4.3 |
| M36 | 37.0 | 37.62 | 66.0 | 5.0 | 4.4 | 5.6 |
When & Where to Use ISO 7089 Washers
Load Distribution
The primary function of ISO 7089 washers is to distribute the clamping force of the bolt or nut over a larger bearing area. This prevents crushing, embedding, and surface damage in softer materials like aluminum, wood, and plastic.
Surface Protection
Washers protect painted or coated surfaces from scratching and galling during tightening. Essential for architectural steel, façade systems, and aesthetic assemblies where bolt head marks are unacceptable.
Joint Integrity
Hardened 300 HV washers prevent embedding under high preload, maintaining consistent clamp force over time. Critical for vibrating machinery, rotating equipment, and transportation applications.
Coastal UAE Projects
For outdoor and marine environments, specify A4-316 stainless steel ISO 7089 washers paired with A4 bolts. Using zinc-plated steel washers with stainless bolts creates a galvanic cell that accelerates corrosion.
Structural Steel
For structural connections using ISO 4014/4017 Grade 8.8 or 10.9 bolts, always use 300 HV hardened washers per ISO 7089. This is mandatory in many building codes to prevent bearing failure and ensure consistent friction in slip-critical joints.
Complete RFQ Format
"ISO 7089 M16 plain washer, normal series, 300 HV hardened steel, zinc plated Cr3+, Product Grade A."
Complementary Washer & Fastener Standards
| Standard | Description | When to Use |
|---|---|---|
| ISO 7090 | Plain washers, chamfered — Normal series, Grade A | When bolt fillet radius requires chamfer clearance |
| ISO 7091 | Plain washers — Normal series, Grade C | General purpose, looser tolerances, lower cost |
| ISO 7092 | Plain washers — Small series, Grade A | Space-constrained assemblies, smaller OD |
| ISO 7093 | Plain washers — Large series, Grade A | Soft materials needing larger bearing surface |
| ISO 7094 | Plain washers — Extra large series, Grade C | Timber, plastic, very soft substrates |
| DIN 125-A | Plain washers, unchamfered | Legacy drawings, German machinery |
| DIN 125-B | Plain washers, chamfered | Legacy drawings requiring chamfer |
| DIN 6916 | Hardened washers for structural bolting | HV structural connections, DIN standard |
| ASTM F436 | Hardened steel washers (inch series) | ASTM A325 / A490 structural bolting |
| ISO 4014 / 4017 | Hexagon head bolts | Mating bolts for ISO 7089 washers |
Frequently Asked Questions
Need ISO 7089 Washers in UAE?
We stock ISO 7089 plain washers in 200 HV and 300 HV carbon steel, A2-304 and A4-316 stainless steel, with zinc plating, HDG, and plain finishes. Same-day dispatch from RAK FREEZONE across UAE & GCC.
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