ISO 7089, 7090 & 7091 Stainless Steel Washers
ISO 7089 is the international standard for the plain washer, normal series, product grade A. ISO 7090 is the same washer with a chamfer on the outside diameter, and ISO 7091 is the normal series in the coarser product grade C. We stamp all three in 304, 316 and 316L at our Jiaxing factory. This page is about the standards themselves: what each one covers, how the numbers map to DIN 125 and GB/T, how to write the designation, and what to send us for a quote.
ISO 7089, 7090 and 7091 side by side
All three are plain round washers in the normal outside-diameter series. They differ in product grade (the tolerance class set by ISO 4759-3), in whether the outside edge is chamfered, and in hardness class.
ISO 7089 is the plain washer, normal series, product grade A. ISO 7090 is the same washer chamfered at the outside diameter. ISO 7091 is the normal series in product grade C, written for steel in the 100 HV class. For stainless steel, ISO 7089 and ISO 7090 give one hardness class, 200 HV.
| Property | ISO 7089 | ISO 7090 | ISO 7091 |
|---|---|---|---|
| Title | Plain washers, normal series, product grade A | Plain washers, chamfered, normal series, product grade A | Plain washers, normal series, product grade C |
| Product grade and tolerances | Grade A, ISO 4759-3 | Grade A, ISO 4759-3 | Grade C, ISO 4759-3 (the coarser grade) |
| Chamfer | None | Chamfered at the outside diameter | None |
| Hardness class, steel | 200 HV or 300 HV | 200 HV or 300 HV | 100 HV |
| Hardness class, stainless | 200 HV (grades A2, F1, C1, A4, C4 of ISO 3506-1) | 200 HV (same grades) | Not listed. Other materials as agreed between buyer and supplier. |
| Nominal sizes | 1.6 to 64 mm | 5 to 64 mm | 1.6 to 64 mm |
| Used with | Grade A and B hexagon bolts and screws up to property class 8.8 (200 HV) or 10.9 (300 HV); stainless fasteners of similar composition | The same bolts and screws as ISO 7089; the chamfered edge is the difference | Grade C hexagon bolts and screws up to property class 6.8 |
| DIN equivalent | DIN 125 Form A | DIN 125 Form B | DIN 126 |
| GB/T equivalent | GB/T 97.1 | GB/T 97.2 | GB/T 95 |
For a given thread size the outside diameter and thickness are the same in all three. The clearance hole is not: ISO 7091 gives a larger hole than ISO 7089 at every size in the table further down this page, so do not swap a grade C washer for a grade A one on bore alone.
What ISO 7089 specifies
ISO 7089:2000 covers plain washers, normal series, product grade A, for nominal thread diameters from 1.6 mm to 64 mm, in the 200 HV and 300 HV hardness classes. Table 3 of the standard sets the material and hardness as follows.
| Material | Hardness class | Hardness range | Surface |
|---|---|---|---|
| Steel | 200 HV | 200 to 300 HV | Plain: natural finish, protective lubricant or other coating as agreed |
| Steel, hardened and tempered | 300 HV | 300 to 370 HV | Plain, or coated as agreed; plating and coating processes chosen to avoid hydrogen embrittlement |
| Stainless steel (A2, F1, C1, A4, C4 per ISO 3506-1) | 200 HV | 200 to 300 HV | Plain, natural finish |
Stainless is one hardness class
The standard gives stainless washers only the 200 HV class, so a stainless ISO 7089 washer is always written with 200 HV and its steel grade (see the designation below). A 300 HV washer is a hardened and tempered steel part, not a stainless one.
Sizes and tolerances
Tolerances come from ISO 4759-3, product grade A. If a size is not in the standard's list, ISO 887 is the reference for it. The standard also tells the user to check suitability when soft material is clamped or when the clearance hole in the workpiece is large.
ISO 7089 nominal dimensions
These are the nominal dimensions for the sizes most often drawn, in millimetres. They are the same as DIN 125 Form A, so for tolerances and the full size range use the DIN 125 flat washer page.
| Thread size | Inner Ø d1 (mm) | Outer Ø d2 (mm) | Thickness s (mm) |
|---|---|---|---|
| M2 | 2.2 | 5 | 0.3 |
| M2.5 | 2.7 | 6 | 0.5 |
| M3 | 3.2 | 7 | 0.5 |
| M4 | 4.3 | 9 | 0.8 |
| M5 | 5.3 | 10 | 1.0 |
| M6 | 6.4 | 12 | 1.6 |
| M8 | 8.4 | 16 | 1.6 |
| M10 | 10.5 | 20 | 2.0 |
| M12 | 13 | 24 | 2.5 |
| M14 | 15 | 28 | 2.5 |
| M16 | 17 | 30 | 3.0 |
| M20 | 21 | 37 | 3.0 |
| M24 | 25 | 44 | 4.0 |
| M30 | 31 | 56 | 4.0 |
| M36 | 37 | 66 | 5.0 |
ISO 7090 uses the same values from M5 up. We make M2 to M64.
How the ISO numbers relate to DIN, GB/T and ASME
The same part often arrives on a drawing under four different numbers. This is how they line up.
DIN 125 and DIN 126
DIN 125 Form A is ISO 7089 and Form B is ISO 7090. DIN 126, the grade C washer, was replaced by DIN EN ISO 7091. The German foreword to EN ISO 7089 and EN ISO 7090 records that the 1990 editions of DIN 125 parts 1 and 2 were superseded by the two ISO standards. See the DIN 125 page for the full size chart.
GB/T 97.1, 97.2 and 95
The Chinese standards catalogue lists GB/T 97.1-2002 as an equivalent adoption of ISO 7089:2000. GB/T 97.2 and GB/T 95 are listed there as modified adoptions of ISO 7090 and ISO 7091, so check a GB/T 95 drawing against its own table rather than against ISO 7089. Details on the GB/T flat washer page.
ISO 7092 and ISO 7093
ISO 7092 is the small series, product grade A, for nominal sizes 1.6 to 36 mm, with a smaller outside diameter than the normal series. ISO 7093 is the large series, with a larger outside diameter; part 1 covers product grade A. Both are separate standards from ISO 7089.
ASME
ISO 7089 is a metric standard. The inch washers in ASME B18.21.1 (USS and SAE) use a different size system and are not a swap for it. ASME also publishes B18.22M for metric plain washers; if your drawing calls that out, send it and we compare it with ISO 7089 before quoting. The cross-reference guide covers the inch series.
How to order ISO 7089 washers in stainless
Write the designation the way the standard does, and a quote is quick to turn around.
Washer ISO 7089-8-200 HV-A2
A normal-series, product grade A plain washer of nominal size 8 mm, hardness class 200 HV, in grade A2 stainless steel. Use A4 in place of A2 for 316 and 316L material.
| Washer | Designation |
|---|---|
| Chamfered, stainless A2, 200 HV | Washer ISO 7090-8-200 HV-A2 |
| Grade C, steel, 100 HV | Washer ISO 7091-8-100 HV |
What to send for a quote
- The standard and form on your drawing: ISO 7089, 7090 or 7091, or the DIN 125 A or B, DIN 126 or GB/T number.
- Thread size, for example M8.
- Material: 304, 316 or 316L. Material and hardness are specified on the order, so state the hardness class if your drawing sets one.
- Finish: bright as standard, polished on request.
- Quantity, and FOB or CIF with the destination port.
- We verify the grade with our own handheld XRF spectrometer (PMI) and can include the reading with your order; a test report from an independent third-party lab is available on request.
We reply in about one business day. Not sure which grade or form to specify? Send the drawing and we will say what it calls for. The 304 vs 316 guide covers the material choice.
ISO 7089 questions, answered.
What buyers ask before ordering plain washers to the ISO numbers. Have one we have not covered? Ask our team.
What is ISO 7089?
ISO 7089 is the international standard for plain washers, normal series, product grade A. It covers round flat washers for nominal thread diameters from 1.6 mm to 64 mm in the 200 HV and 300 HV hardness classes, and stainless steel washers are given the 200 HV class. Tolerances follow ISO 4759-3. The edition is ISO 7089:2000.
ISO 7089 vs DIN 125: are they the same?
DIN 125 Form A is the plain, unchamfered washer and carries the same nominal bore, outside diameter and thickness as ISO 7089. The German foreword to EN ISO 7089 states that the 1990 editions of DIN 125 parts 1 and 2 were superseded by EN ISO 7089 and EN ISO 7090. A drawing that says DIN 125 A and one that says ISO 7089 call for the same washer, and we supply to the designation on your drawing.
ISO 7089 vs ISO 7090: what is the difference?
The chamfer. ISO 7090 is chamfered at the outside diameter and ISO 7089 is not. Both are product grade A with the same hardness classes, and at the sizes both cover (5 mm and up) they share the same clearance hole, outside diameter and thickness. ISO 7090 corresponds to DIN 125 Form B and GB/T 97.2.
ISO 7089 vs ISO 7091: what is the difference?
Product grade and hardness. ISO 7091 is product grade C, the coarser tolerance class, and the standard lists steel in the 100 HV class, for grade C bolts and screws up to property class 6.8. The outside diameter and thickness match ISO 7089, but the clearance hole is larger. ISO 7091 corresponds to DIN 126 and GB/T 95. ISO 7089 and ISO 7090 are the two that list stainless grades.
How do I order ISO 7089 washers in stainless?
Write the designation as the standard does, for example Washer ISO 7089-8-200 HV-A2 for an M8 washer in A2 stainless, with A4 for 316 or 316L. Send us the standard, thread size, material (304, 316 or 316L), quantity and delivery term, and tell us if you need a PMI reading or a third-party lab report. We quote in about one business day.
Related pages
DIN 125 flat washers
The German-standard equivalent of ISO 7089, with the full M2 to M64 size chart.
View DIN 125 pageStandards guides
The ISO flat-washer family explained, and DIN, ISO, ASME and GB/T side by side.
ISO washer standardsTell us what you need.
Send the designation or a drawing and we will come back with pricing, lead time and material options. No account, no minimum to ask.
- 304 / 316 / 316L, ISO 7089 / 7090 / 7091 or custom
- Replies from engineers, typically within one business day
- XRF grade check (PMI), third-party lab report on request
- FOB Ningbo / CIF, HS 7318.22