---
title: "Countersunk Washers (90° Seat)"
description: "Countersunk Washers (90° Seat) to Trade series (90° countersunk washer): sizes M4 to M10, id 4.3-10.5 mm, od 11-24 mm. Technical drawing redraws to any row."
url: https://engineeringhardware.com/fastener/countersunk-washers/
source: Engineering Hardware & Fasteners
---

# Countersunk Washers (90° Seat)

Washers · Countersunk & Finishing Washers

5 catalogued sizes, dimensioned to Trade series (90° countersunk washer). Pick any row and the technical drawing redraws to it.

Countersunk Washers (90° Seat) to Trade series (90° countersunk washer) are catalogued in sizes M4 to M10, with id 4.3-10.5 mm, od 11-24 mm, thick 2-4 mm. 5 sizes are held in the table below, and the technical drawing redraws to whichever row you select.

- **Standard:** Trade series (90° countersunk washer)
- **Size range:** M4-M10
- **ID:** 4.3-10.5 mm
- **OD:** 11-24 mm
- **Catalogued sizes:** 5

Dimensions are nominal values from the governing standard. Confirm the tolerance class for your application before ordering.

![Countersunk Washers (90° Seat) technical product image](https://engineeringhardware.com/wp-content/uploads/2026/08/Countersunk-Washers.webp)

Product catalog

## Related Countersunk & Finishing Washers products

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[View all Countersunk, Cup & Finishing Washers →](https://engineeringhardware.com/fastener-products/washers/countersunk-cup-finishing-washers/) [Full product catalog](https://engineeringhardware.com/products/)

## Materials & Grades

Select a material class to see the grades we supply it in. Each designation is listed with its ISO/EN, AISI/SAE, JIS and GB equivalents.

Stainless Steel38 Carbon Steel66 Alloy Steel41 Bearing Steel5 Spring Steel25 Aluminum and Aluminum Alloys21 Brass17 Bronze11 Copper8 Titanium and Titanium Alloys18 Nickel and Nickel Alloys22 Iron-Nickel and High-Temperature Alloys10 Tool Steel and Specialty Hardened Steel9 Structural and Construction Steel9

### Stainless Steel

#### Austenitic Stainless Steel

- A1 AISI 303 · SAE 303 · SUS303 · EN 1.4305 · X8CrNiS18-9
- A2 AISI 304 · SAE 304 · SUS304 · EN 1.4301 · X5CrNi18-10 · 06Cr19Ni10
- 304L AISI 304L · SUS304L · EN 1.4307 · X2CrNi18-9 · 022Cr19Ni10
- 302 AISI 302 · SUS302 · EN 1.4310
- 305 AISI 305 · SUS305 · EN 1.4303
- A4 AISI 316 · SAE 316 · SUS316 · EN 1.4401 · X5CrNiMo17-12-2 · 06Cr17Ni12Mo2
- 316L AISI 316L · SUS316L · EN 1.4404 · X2CrNiMo17-12-2 · 022Cr17Ni12Mo2
- 321 AISI 321 · SUS321 · EN 1.4541 · X6CrNiTi18-10
- 310 / 310S AISI 310 · AISI 310S · SUS310S · EN 1.4845
- 302HQ AISI 302HQ
- A3
- A5
- 347 AISI 347 · SUS347 · EN 1.4550 · X6CrNiNb18-10
- 309 / 309S AISI 309 · AISI 309S · SUS309S

#### Martensitic Stainless Steel

- AISI 410 SUS410 · EN 1.4006 · X12Cr13 · 12Cr13
- AISI 420 SUS420J1 · SUS420J2 · EN 1.4021 · EN 1.4028 · 20Cr13 · 30Cr13
- AISI 431 SUS431 · EN 1.4057 · X17CrNi16-2
- C1
- C3
- C4
- AISI 440A
- AISI 440B
- AISI 440C SUS440C · EN 1.4125

#### Ferritic Stainless Steel

- AISI 430 SUS430 · EN 1.4016 · X6Cr17 · 10Cr17
- F1
- AISI 434
- AISI 444

#### Precipitation-Hardening Stainless Steel

- 17-4 PH AISI 630 · UNS S17400 · SUS630 · EN 1.4542 · X5CrNiCuNb16-4
- 15-5 PH UNS S15500
- 17-7 PH UNS S17700

#### Duplex and Super Duplex Stainless Steel

- Duplex 2205 UNS S31803 · UNS S32205 · EN 1.4462
- Super Duplex 2507 UNS S32750 · EN 1.4410
- D2
- D4
- D6
- D8
- Lean Duplex 2101 UNS S32101
- Super Duplex S32760 UNS S32760 · EN 1.4501

### Carbon Steel

#### Low-Carbon Steel

- SAE 1006
- SAE 1008
- SAE 1010
- SAE 1018
- SAE 1020
- Q195
- Q235
- SAE 1012
- SAE 1015
- Q215
- ML08
- ML08Al
- ML10
- ML15
- ML20
- SWRCH6A
- SWRCH8A
- SWRCH10A
- SWRCH12A
- SWRCH15A
- SWRCH18A

#### Medium-Carbon Steel

- SAE 1035
- SAE 1045
- S45C
- C45
- SAE 1030
- SAE 1040
- SAE 1050
- 30
- 35
- 40
- 45
- 50
- S35C
- S40C
- S50C
- C35
- C40

#### High-Carbon Steel

- SAE 1060
- SAE 1070
- 65Mn
- SAE 1065
- SAE 1075
- SAE 1080
- SAE 1085
- SAE 1090
- SAE 1095
- 60
- 65
- 70
- 75
- 80
- 85

#### Cold-Heading Steel

- SWRCH22A
- 10B21
- SWRCH22K
- SWRCH25K
- SWRCH30K
- SWRCH35K
- SWRCH40K
- ML20Mn
- ML25
- ML30
- ML35
- ML40
- 15B25

### Alloy Steel

#### Chromium Steel

- 40Cr
- 45Cr
- AISI 5140
- SAE 5140
- AISI 5120
- SAE 5120
- SCr420
- SCr440

#### Chromium-Molybdenum Steel

- 35CrMo
- 42CrMo
- AISI 4140
- SCM435
- SCM440
- 42CrMo4
- 30CrMo
- AISI 4130
- SAE 4130
- SAE 4140
- AISI 4142
- AISI 4145
- SCM415
- SCM420
- SCM445
- EN 1.7220
- EN 1.7225
- 25CrMo4
- 34CrMo4

#### Nickel-Chromium-Molybdenum Steel

- AISI 4340
- SAE 4340
- 40CrNiMo
- SNCM439
- EN 1.6511
- 36CrNiMo4

#### Boron Alloy Steel

- 10B22
- 10B21
- 15B21
- 15B25
- 20MnTiB
- 20Mn2B
- 35VB
- 40MnB

### Bearing Steel

#### Bearing Steel

- GCr15
- AISI 52100 SAE 52100 · UNS G52986
- SUJ2
- 100Cr6 EN 1.3505
- GCr15SiMn

### Spring Steel

#### Carbon Spring Steel

- SAE 1065
- SAE 1070
- SAE 1075
- SAE 1080
- SAE 1095
- 65
- 70
- 75
- 80
- 65Mn

#### Silicon-Manganese Spring Steel

- 60Si2Mn
- 60Si2MnA
- SUP6
- SUP7

#### Chromium-Vanadium Spring Steel

- 50CrVA
- SAE 6150
- AISI 6150
- SUP10

#### Stainless Spring Steel

- AISI 301
- SUS301
- EN 1.4310
- AISI 302
- AISI 304
- AISI 316
- 17-7 PH

### Aluminum and Aluminum Alloys

#### Commercially Pure Aluminum

- 1050
- 1060
- 1070
- 1100

#### 2xxx Series Aluminum

- 2024
- 2011
- 2014
- 2017

#### 5xxx Series Aluminum

- 5052
- 5083
- 5754

#### 6xxx Series Aluminum

- 6061
- 6061-T6
- 6063
- 6082
- 6082-T6

#### 7xxx Series Aluminum

- 7075
- 7075-T6
- 7005
- 7050
- 7075-T73

### Brass

#### Free-Cutting Brass

- C36000
- H62
- HPb59-1
- C3601
- C3602
- C3604
- CuZn36Pb3
- CuZn39Pb3
- EN CW614N
- EN CW617N
- H65

#### Lead-Free Brass

- C69300
- C27450
- CW510L
- CW511L

#### Naval Brass

- C46400
- CuZn39Sn1

### Bronze

#### Silicon Bronze

- C65500
- C65100
- C65600

#### Phosphor Bronze

- C51000
- C52100
- CuSn6
- CuSn8

#### Aluminum Bronze

- C95400
- C95500
- C63000
- CuAl10Ni5Fe4

### Copper

#### Copper

- C11000
- T2
- C10100
- C10200
- C12200
- T1
- TU1
- TU2

### Titanium and Titanium Alloys

#### Commercially Pure Titanium

- Grade 2
- Grade 1
- Grade 3
- Grade 4
- TA1
- TA2
- TA3

#### Alpha-Beta Titanium Alloys

- Grade 5
- Ti-6Al-4V
- TC4
- UNS R56400

#### Low-Interstitial Grade

- Grade 23
- Ti-6Al-4V ELI
- UNS R56407

#### Other Titanium Fastener Alloys

- Ti-6Al-6V-2Sn
- Ti-6Al-2Sn-4Zr-2Mo
- Beta-C titanium
- Ti-10V-2Fe-3Al

### Nickel and Nickel Alloys

#### Commercially Pure Nickel

- Nickel 200
- UNS N02200
- Nickel 201
- UNS N02201

#### Inconel Alloys

- Inconel 625 UNS N06625
- Inconel 718 UNS N07718
- Inconel 600 UNS N06600
- Inconel 601 UNS N06601
- Inconel 686 UNS N06686
- Inconel X-750 UNS N07750

#### Monel Alloys

- Monel 400 UNS N04400
- Monel K-500 UNS N05500

#### Hastelloy Alloys

- Hastelloy C-276 UNS N10276
- Hastelloy C-22 UNS N06022
- Hastelloy B-2 UNS N10665
- Hastelloy B-3 UNS N10675
- Hastelloy X UNS N06002

#### Other Nickel Alloys

- Alloy 20 UNS N08020
- Alloy 625
- Alloy 718
- Alloy 825 UNS N08825
- Alloy 925 UNS N09925

### Iron-Nickel and High-Temperature Alloys

#### A286

- A-286
- UNS S66286
- EN 1.4980

#### Invar

- Invar 36
- Alloy 36
- UNS K93600
- FeNi36

#### Alloy 42

- Alloy 42
- UNS K94100
- FeNi42

### Tool Steel and Specialty Hardened Steel

#### Tool Steel and Specialty Hardened Steel

- AISI D2
- AISI H13
- SKD11
- Cr12MoV
- AISI O1
- AISI A2
- AISI S7
- SKD61
- 9CrSi

### Structural and Construction Steel

#### Structural and Construction Steel

- ASTM A36
- Q235B
- Q355B
- S355JR
- Q235C
- Q355C
- S235JR
- S275JR
- S355J2

## Applications & Industries

What Countersunk Washers are specified for, industry by industry. Stocked from M4 to M10 (nominal bolt size).

### Industries that specify Countersunk Washers

- **Timber & construction:** Large-diameter washers that stop pull-through in softer material.
- **Rotating & vibrating plant:** Spring, tooth and wedge types that maintain or lock bolt tension.
- **Steel fabrication:** Spreading load under a head or nut and protecting the surface finish.
- **Machine building & OEM:** Setting bearing area on soft alloy, plastic and oversized holes.

![Countersunk Washers in use — application photograph](https://engineeringhardware.com/wp-content/uploads/2026/09/Countersunk-Washers-Detail.webp)

### Typical applications

- protecting a painted or plated surface under a turned nut
- maintaining bolt tension in a joint that settles
- spreading clamp load over a soft or oversized bearing face

### Service conditions to specify against

- **Marine and coastal:** Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
- **Hardness matters:** Under a high-strength bolt a soft washer embeds into the joint and preload is lost — specify a hardened washer for structural bolting.

[Full application guide: where Countersunk Washers are used, how to specify them, and the cases they are wrong for](https://engineeringhardware.com/applications/countersunk-washers/)

## Technical Drawing

Dimensioned line drawing of M4 Countersunk Washers (90° Seat) to Trade series (90° countersunk washer). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

- **Inner diameter d1 (mm):** 4.3
- **Outer diameter d2 (mm):** 11.0
- **Thickness t (mm):** 2.0
- **Countersink angle:** 90
- **Material:** Stainless A2
- **Finish:** Passivated
- **Note:** Matches ISO 7046 heads

## Dimensions & Specifications (Trade series (90° countersunk washer))

Every row below is a starting point for the customizer above — pick any size and the drawing will redraw to that row.

| For screw size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Countersink angle | Material | Finish | Note |
| --- | --- | --- | --- | --- | --- | --- | --- |
| [M4](https://engineeringhardware.com/guide/size/m4-countersunk-washers/) | 4.3 | 11.0 | 2.0 | 90 | Stainless A2 | Passivated | Matches ISO 7046 heads |
| [M5](https://engineeringhardware.com/guide/size/m5-countersunk-washers/) | 5.3 | 13.0 | 2.5 | 90 | Stainless A2 | Passivated | Matches ISO 7046 heads |
| [M6](https://engineeringhardware.com/guide/size/m6-countersunk-washers/) | 6.4 | 16.0 | 3.0 | 90 | Stainless A2 | Passivated | Matches ISO 7046 heads |
| [M8](https://engineeringhardware.com/guide/size/m8-countersunk-washers/) | 8.4 | 20.0 | 3.5 | 90 | Stainless A2 | Passivated | Matches ISO 10642 heads |
| [M10](https://engineeringhardware.com/guide/size/m10-countersunk-washers/) | 10.5 | 24.0 | 4.0 | 90 | Steel | Zinc plated | Matches ISO 10642 heads |

Countersunk Washers (90° Seat) conform to Trade series (90° countersunk washer). As washers, they are specified by the dimensions in the table below; this page also covers materials, finishes and typical uses.

## What Are Countersunk Washers (90° Seat)?

Countersunk Washers (90° Seat) are washers defined by Trade series (90° countersunk washer). They are selected by nominal bolt size and the dimensional characteristics shown below, and are available in a range of materials and finishes to suit the application and environment.

## Materials & Finishes

Common materials include carbon steel (typically zinc plated or hot-dip galvanized), hardened or case-hardened steel where wear matters, and stainless steel A2 (304) or A4 (316) for corrosion resistance. Specify the material, hardness where relevant, and the surface finish appropriate to your application and environment.

## Pricing

Countersunk Washers (90° Seat) are supplied to order. Pricing starts from approximately US$0.050 per piece for standard sizes in carbon steel; final pricing depends on size, material, finish and order quantity (MOQ applies). Submit your exact configuration with the quote form above.

Custom manufacturing · Made to drawing

## Need a countersunk washers (90° seat) outside the standard range?

Bore, outside diameter, thickness, temper and finish are the variables here — there is no thread to specify, so the fit and the bearing area are what the drawing has to pin down. Made by stamping or punching.

Minimum order from 2,000 pieces; samples within 7 days of drawing approval.

[Custom washer manufacturing](https://engineeringhardware.com/custom/washers/)[Send a drawing](https://engineeringhardware.com/custom/washers/#rfq)

Inside the plant

## Manufactured in our own plant

This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided.

1. ![Wire rod feeding into a cold heading machine](https://engineeringhardware.com/wp-content/uploads/2026/08/09-wire-rod-feed-cold-heading-machine.webp) 01 **Cold heading** Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail. Head dimensions and under-head radius checked at set-up and per shift.
2. ![Thread rolling machine producing bolt threads](https://engineeringhardware.com/wp-content/uploads/2026/08/03-thread-rolling-machine-bolt-production.webp) 02 **Thread rolling** Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch. Go / no-go ring gauges to ISO 965 tolerance class 6g.
3. ![Baskets of bolts staged for heat treatment](https://engineeringhardware.com/wp-content/uploads/2026/08/05-heat-treatment-baskets-black-bolts.webp) 03 **Heat treatment** Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it. Core hardness and tensile tested per lot to ISO 898-1.
4. ![Zinc plated bolts in a treatment basket](https://engineeringhardware.com/wp-content/uploads/2026/08/23-zinc-plated-bolts-treatment-basket.webp) 04 **Surface treatment** Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list. Coating thickness and neutral salt spray hours to ISO 9227.

## Frequently Asked Questions

### Which standard governs Countersunk Washers (90° Seat)?

Countersunk Washers (90° Seat) are manufactured to Trade series (90° countersunk washer). The dimensional values on this page follow that standard.

### What is the size range of Countersunk Washers (90° Seat)?

The table on this page lists 5 sizes for Countersunk Washers (90° Seat), ranging from M4 to M10. Sizes outside the table can be quoted on request.

### In which materials are Countersunk Washers (90° Seat) supplied?

Countersunk Washers (90° Seat) are supplied in carbon steel (zinc plated / HDG) and stainless A2 / A4, with finishes including zinc plating, hot-dip galvanizing and black oxide. Choose material and finish to suit the load and the service environment for Countersunk Washers (90° Seat).

### How do I request a quotation?

Use the parametric drawing on this page to set the exact configuration (size, material, finish) and click "Request this configuration" — a specialist from Engineering Hardware will respond within one business day.