DIN 9021 Fender Washers (Large OD) — 304 & 316 Stainless
DIN 9021 is the large-outer-diameter flat washer — outside diameter roughly 3× the bolt, compared to 2–2.5× for a standard DIN 125 washer. That wider bearing face spreads clamping load across soft, slotted or oversized holes where a standard-OD washer would pull through or compress unevenly. We manufacture DIN 9021 fender washers at our Jiaxing factory in 304, 316 and 316L stainless steel, M3–M24, from traceable documented melts. MTC (EN 10204 3.1) and PMI available on request.
DIN 9021 dimensions (nominal mm)
Nominal dimensions for DIN 9021 large-OD fender washers. Note the outer diameter — at M8 it is 24 mm vs 16 mm for DIN 125; at M12 it is 37 mm vs 24 mm. All values in millimetres.
| Thread size | Inner Ø d1 (mm) | Outer Ø d2 (mm) | Thickness s (mm) |
|---|---|---|---|
| M3 | 3.2 | 9 | 0.8 |
| M3.5 | 3.7 | 11 | 0.8 |
| M4 | 4.3 | 12 | 1.0 |
| M5 | 5.3 | 15 | 1.2 |
| M6 | 6.4 | 18 | 1.6 |
| M7 | 7.4 | 22 | 2.0 |
| M8 | 8.4 | 24 | 2.0 |
| M10 | 10.5 | 30 | 2.5 |
| M12 | 13 | 37 | 3.0 |
| M14 | 15 | 44 | 3.0 |
| M16 | 17 | 50 | 3.0 |
| M18 | 20 | 56 | 4.0 |
| M20 | 22 | 60 | 4.0 |
| M24 | 26 | 72 | 5.0 |
Dimensions nominal (mm) per the standard; tolerances per standard. Larger sizes / inch on request.
Made to product grade A.
All HUIHUI DIN 9021 washers are produced to DIN 9021 / ISO 7093, product grade A — the standard precision grade. Dimensional tolerances follow the standard:
| Dimension | Tolerance direction | Example (M8) |
|---|---|---|
| Inner Ø d1 | plus only (0 / +) | 8.4 → 8.62 mm |
| Outer Ø d2 | minus only (0 / −) | 24 → 23.48 mm |
| Thickness s | symmetrical (±) | 2.0 mm (2.0–2.2) |
The full per-size minimum/maximum table to DIN 9021 / ISO 7093, plus a dimensional inspection report to your AQL, are supplied with the order on request — together with the material certificate (MTC, EN 10204 3.1) and PMI. Tighter tolerances on specific features can be held on custom parts; send your drawing.
DIN 9021 vs DIN 125 vs other large-OD washers
The washer standard controls the OD, not just the bolt-hole. Choosing between DIN 9021 and DIN 125 is a load-distribution decision, not a preference.
DIN 9021 — large OD (this page)
Outside diameter approximately 3× the bolt. Designed to spread load across a wide area — the correct part for slotted holes, oversized clearances, sheet metal, timber, rubber gaskets, strut/channel, and plastic panels where a standard washer would pull through. Inner bore and thickness are DIN-specified for each bolt size. See all flat washer types →
DIN 125 — standard OD
Outside diameter roughly 2–2.5× the bolt. The general-purpose metric flat washer for standard clearance holes and solid bearing surfaces. DIN 125 Form A is dimensionally equivalent to ISO 7089. If your hole is standard and your substrate is solid metal, DIN 125 is the right and more economical choice. See DIN 125 page →
USS / SAE Fender — inch equivalent
The US equivalent of the large-OD concept. USS and SAE fender washers carry the same design intent — wide OD to spread load — but dimensions are in inches and follow ASME B18.22.1. If your drawing calls for USS or SAE fender washers, send us the dimension table and we will quote to exact specs. Available in 304 and 316 stainless.
Material: 304, 316 or 316L
DIN 9021 fender washers are produced in all three standard stainless grades. Grade choice is driven by the corrosion environment of the installation.
304 — the standard grade
18% chromium, 8% nickel. Correct for indoor structural, architectural, food-equipment and most non-aggressive outdoor applications. Fender washers in 304 are the default specification for timber framing, equipment mounting on steel channel, and general fabrication where the environment is not chloride-aggressive. Cost-effective and widely stocked.
316 & 316L — for chloride exposure
The added molybdenum in 316 (2–3%) gives substantially better resistance to chloride pitting and crevice corrosion. Specify 316 or 316L for marine and coastal installations, chemical-process equipment, de-icing zones, and any application where salt spray or chloride contact is present. 316L (low carbon) is the correct choice when the washer is part of a welded assembly — lower carbon prevents sensitisation at the heat-affected zone.
Bright (as-stamped mill finish) as standard — clean, consistent and practical for structural and industrial supply. Polished finish available on request for architectural, food-grade or visible-fastener applications. Finish is a surface detail; corrosion performance is determined by the grade, not the surface finish.
How we make DIN 9021 fender washers
The large OD on a DIN 9021 washer puts more material under the press — feed accuracy and coil grade matter more, not less, than on a standard-OD part.
1. High-speed coil-fed pressing
We run JH21-series power presses fitted with automatic coil feeders — stainless strip feeds straight off the reel into the die at a controlled pitch. No manual blank loading means no operator-to-operator variation in feed position. For a DIN 9021 M12 (OD 37 mm), the die pitch and stroke rate are set once and held for the run. That consistency is how you maintain a 37.0 mm OD across a full production batch, not just spot-check samples.
2. Genuine full-spec stainless
Material is sourced from documented stainless melts with traceable heat numbers. We stamp to the full nominal thickness specified in DIN 9021 — not under-gauge strip sourced to cut cost. When you specify 316L, the PMI will confirm it on the finished part. Recycled or mixed-grade strip is not used in any production run. Every coil is logged against the order on receipt.
3. ISO 9001:2015 QC, MTC on request
Our quality management system is certified to ISO 9001:2015 (cert No. 74326Q00174R001). Inspection covers incoming coil verification, in-process dimensional checks at set intervals, and pre-shipment sampling. For export orders requiring compliance documentation:
- MTC (EN 10204 3.1) — mill test certificate tracing heat number, chemical composition and mechanical properties. Available on request at no extra charge for standard orders.
- PMI — positive material identification by XRF, confirming grade on finished parts. Available on request for critical or regulatory applications.
- First-article inspection — available for new tooling or non-standard sizes; dimensional report issued before bulk shipment.
Shipment terms FOB Ningbo or CIF to your port. HS code 7318.22.
DIN 9021 questions, answered.
The specification questions engineers and procurement teams ask most about DIN 9021 fender washers. Have one we have not covered? Ask our team.
What is a DIN 9021 washer and how does it differ from DIN 125?
DIN 9021 is the large-outer-diameter flat washer — often called a fender washer or penny washer. Its outside diameter is approximately 3× the nominal bolt diameter, compared to roughly 2–2.5× for a standard DIN 125 washer. The larger bearing face distributes clamping force across a wider area, which is the correct design choice when the substrate is soft (timber, plastics, rubber), the hole is oversized, or the hole is slotted. For standard clearance holes in solid material, DIN 125 is the right part. See all flat washer types →
What sizes do you supply in DIN 9021?
The standard DIN 9021 range runs from M3 through M24. The full size chart on this page lists every standard thread size with exact inner diameter, outer diameter and thickness in millimetres. Larger sizes and non-standard dimensions are available on request — send the specification and quantity and we will quote within one business day.
Which stainless grade — 304 or 316 — should I specify for DIN 9021 fender washers?
304 (A2) is appropriate for indoor structural work, food-equipment assembly, architectural hardware and most outdoor environments that are not chloride-aggressive. 316 or 316L (A4) is the correct specification for marine, coastal, chemical-process or de-icing applications where chloride-induced pitting corrosion is a real risk. 316L specifically is recommended for any assembly involving welding, because the lower carbon content prevents sensitisation at the heat-affected zone. If you are unsure, read the full grade comparison or send us the application detail and we will confirm the right grade.
Do DIN 9021 washers have a metric equivalent in ISO or other standards?
DIN 9021 does not have a direct one-to-one ISO equivalent in the same way that DIN 125 aligns with ISO 7089. The large-OD washer concept exists under various national and industry standards with slightly different OD and thickness values. If your drawing references a specific ISO or ASME large-OD washer, send us the dimension table and we will confirm whether DIN 9021 matches or quote to the exact drawing dimensions.
Can you provide MTC and PMI, and what are the shipping terms?
Yes. Mill test certificates (MTC, EN 10204 3.1) tracing heat number, chemical composition and mechanical properties are available on request for all orders. PMI (positive material identification by XRF) can be arranged for compliance-critical exports to confirm grade on finished parts. Shipments go FOB Ningbo or CIF to your named port; HS code 7318.22. MOQ and lead time are flexible and confirmed at the quote stage — send specs and quantities and we reply within one business day.
Tell us what you need.
Send specs or a drawing and we will come back with pricing, lead time and material options. No account, no minimum to ask.
- ✓ 304 / 316 / 316L, DIN 9021 or custom dimensions
- ✓ Replies from engineers, typically within one business day
- ✓ MTC (EN 10204 3.1) and PMI available on request
- ✓ FOB Ningbo / CIF · HS 7318.22