ISO 7091 Plain Washers (Product Grade C)
ISO 7091 plain washers, product grade C — the unchamfered, wide-tolerance general-purpose flat washer for rough bolting, nominal sizes 1,6 to 64, with the collected d1/d2/h min-max ladder.
Last updated: 2026-11
Specifications
ISO 7091 is the product-grade-C member of the ISO plain-washer series: a flat, unchamfered ring with wider tolerances than the ISO 7089/7090 grade-A washers, meant for the coarse end of the market — agricultural equipment, structural fabrications, fixtures — where a machined, chamfered seat does not exist and the washer only has to spread the clamp and bridge an oversized hole. The collected ladder runs nominal 1,6 to 64 with per-size min/max on all three attributes (for example nominal 12: bore 13,5–13,93 mm, outside 22,7–24 mm, thickness 2,2–2,8 mm). Because grade C tolerances are broad, do not mix these with ISO 7089/7090 in a tolerance-controlled assembly — compare the two ladders in this catalog and the thickness windows are visibly wider here. Where your joint needs a chamfered seat or a tighter bore, step up to the ISO 7090 page; where it needs the largest possible bearing face, see ISO 7093. Material and finish are not tabulated by the collected specification — per RFQ (state the exposure, since plain grade-C washers are commonly self-colour or zinc-coated depending on service).
| Standard | ISO 7091 — plain washers, product grade C (unchamfered, normal series) |
|---|---|
| Size range | Nominal sizes 1,6 – 64 (19 sizes tabulated) |
| Hole diameter | d1: nominal = min., max. per size (e.g. nominal 12: 13,5 / 13,93 mm) |
| Outside diameter | d2: nominal = max., min. per size (e.g. nominal 12: 24 / 22,7 mm) |
| Thickness | h: nominal / max. / min. per size (e.g. nominal 12: 2,5 / 2,8 / 2,2 mm) |
| Material / finish | Not tabulated by the collected specification — per RFQ |
| Nominal size | d1 Nominal = min. | d1 Max. | d2 Nominal = max. | d2 min. | h Nominal | h max. | h min. |
|---|---|---|---|---|---|---|---|
| 1,6 | 1,8 | 2,05 | 4 | 3,25 | 0,3 | 0,4 | 0,2 |
| 2 | 2,4 | 2,65 | 5 | 4,25 | 0,3 | 0,4 | 0,2 |
| 2,5 | 2,9 | 3,15 | 6 | 5,25 | 0,5 | 0,6 | 0,4 |
| 3 | 3,4 | 3,7 | 7 | 6,1 | 0,5 | 0,6 | 0,4 |
| 4 | 4,5 | 4,8 | 9 | 8,1 | 0,8 | 1 | 0,6 |
| 5 | 5,5 | 5,8 | 10 | 9,1 | 1 | 1,2 | 0,8 |
| 6 | 6,6 | 6,96 | 12 | 10,9 | 1,6 | 1,9 | 1,3 |
| 8 | 9 | 9,36 | 16 | 14,9 | 1,6 | 1,9 | 1,3 |
| 10 | 11 | 11,43 | 20 | 18,7 | 2 | 2,3 | 1,7 |
| 12 | 13,5 | 13,93 | 24 | 22,7 | 2,5 | 2,8 | 2,2 |
| 16 | 17,5 | 17,93 | 30 | 28,7 | 3 | 3,6 | 2,4 |
| 20 | 22 | 22,52 | 37 | 35,4 | 3 | 3,6 | 2,4 |
| 24 | 26 | 26,52 | 44 | 42,4 | 4 | 4,6 | 3,4 |
| 30 | 33 | 33,62 | 56 | 54,1 | 4 | 4,6 | 3,4 |
| 36 | 39 | 40 | 66 | 64,1 | 5 | 6 | 4 |
| 42 | 45 | 46 | 78 | 76,1 | 8 | 9,2 | 6,8 |
| 48 | 52 | 53,2 | 92 | 89,8 | 8 | 9,2 | 6,8 |
| 56 | 62 | 63,2 | 105 | 102,8 | 10 | 11,2 | 8,8 |
| 64 | 70 | 71,2 | 115 | 112,8 | 10 | 11,2 | 8,8 |
Materials
- Material and finish specified per RFQ — grade C plain washers are typically plain steel or zinc-coated; state the exposure environment at quotation
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (ISO 7091 Plain Washers (Product Grade C)) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 10,000 pieces. Stock items run 3–7 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
When is a grade C washer the right choice instead of ISO 7089/7090?
When the joint does not need the grade A precision. ISO 7091 carries wider min/max windows on bore, outside diameter and thickness and ships unchamfered, which suits bolted connections into rough holes, wood or cast surfaces where the washer seats itself. The trade-off shows directly in the collected tables: at nominal 12 the thickness window here is 2,2–2,8 mm, while the chamfered ISO 7090 ladder holds a tighter band — if your assembly measures stack height or needs the chamfer to clear a fillet, the grade A page is the one to order from. Neither standard names a material or coating in the collected data, so steel grade and finish stay per RFQ on both.
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support