---
title: "DIN 937 Thin Castle Nuts (DIN 937) Specification"
description: "DIN 937 Thin Castle Nuts (DIN 937): full dimensional table with tolerances. DIN, ISO and ASME equivalents listed side by side."
url: https://engineeringhardware.com/guide/standard/din-937-thin-castle-nuts-din-937/
source: Engineering Hardware & Fasteners
---

# DIN 937 Thin Castle Nuts (DIN 937) Specification

Nuts · DIN 937

Dimensional table, tolerance classes and the DIN / ISO / ASME parts that supersede or match this standard.

DIN 937 specifies the dimensions and tolerances for thin castle nuts (din 937). The full dimensional table is reproduced below, followed by the DIN, ISO and ASME parts that match or supersede it.

- **Standard:** DIN 937
- **Product:** Thin Castle Nuts (DIN 937)
- **Governing standards:** DIN 937

Equivalence between national standards is dimensional, not always metallurgical. Check the property class separately when substituting.

![DIN 937 Thin Castle Nuts (DIN 937) Specification reference image](https://engineeringhardware.com/wp-content/uploads/2026/06/114-Thin-Hex-Castle-Nut-—-GB／T-6181-／-ISO-4035-Series-053-—-GB／T-6181-／-ISO-4035.webp)

The table below lists the dimensions catalogued for thin castle nuts (din 937) under DIN 937. The scope of DIN 937 itself is not summarised here — where a figure matters, confirm it against the published document.

## DIN 937 — Scope

The table below lists the dimensions catalogued for thin castle nuts (din 937) under DIN 937. The scope of DIN 937 itself is not summarised here — where a figure matters, confirm it against the published document.

## Tolerance & Product Grades

Product grade is a concept from dimensional fastener standards and does not apply to DIN 937. Tolerances for this part are the limits shown against each dimension in the table.

## Dimensions Specified by DIN 937

| Thread size | Pitch (mm) | Width across flats s (mm) | Total height m (mm) | Height vs DIN 935 | Slot width n (mm) | Split pin size | Reference standard |
| --- | --- | --- | --- | --- | --- | --- | --- |
| M10 | 1.5 | 17.0 | 8.0 | approx. 70% | 2.8 | 2.5 x 30 | DIN 937 |
| M12 | 1.75 | 19.0 | 10.0 | approx. 71% | 3.5 | 3.2 x 36 | DIN 937 |
| M16 | 2.0 | 24.0 | 13.0 | approx. 76% | 4.5 | 4 x 40 | DIN 937 |
| M20 | 2.5 | 30.0 | 16.0 | approx. 80% | 4.5 | 4 x 50 | DIN 937 |
| M24 | 3.0 | 36.0 | 19.0 | approx. 79% | 5.5 | 5 x 63 | DIN 937 |

## Equivalent Standards

Where direct equivalents exist (ISO ↔ DIN, ISO ↔ ASME), they are listed on the parent Thin Castle Nuts (DIN 937) page.

Always confirm against the dimensions on this page, since some "equivalent" standards differ in tolerances and head geometry.

## When to Specify DIN 937

DIN 937 is still widely used in European mechanical engineering and as a cross-reference on legacy drawings; its ISO equivalent is preferred for new designs.

Custom manufacturing · Made to drawing

## Need a nut to this standard in a non-standard size?

Parts built to DIN 937 are already in the catalog, so a special is usually a variation on existing tooling rather than a new design — which is what keeps the cost down. Made by cold heading or tapping.

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

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

## Technical Drawing

Dimensioned line drawing of M10 Thin Castle Nuts (DIN 937) to DIN 937. Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

- **Pitch (mm):** 1.5
- **Width across flats s (mm):** 17.0
- **Total height m (mm):** 8.0
- **Height vs DIN 935:** approx. 70%
- **Slot width n (mm):** 2.8
- **Split pin size:** 2.5 x 30

## Dimensions & Specifications (DIN 937)

| Thread size | Pitch (mm) | Width across flats s (mm) | Total height m (mm) | Height vs DIN 935 | Slot width n (mm) | Split pin size | Reference standard |
| --- | --- | --- | --- | --- | --- | --- | --- |
| M10 | 1.5 | 17.0 | 8.0 | approx. 70% | 2.8 | 2.5 x 30 | DIN 937 |
| M12 | 1.75 | 19.0 | 10.0 | approx. 71% | 3.5 | 3.2 x 36 | DIN 937 |
| M16 | 2.0 | 24.0 | 13.0 | approx. 76% | 4.5 | 4 x 40 | DIN 937 |
| M20 | 2.5 | 30.0 | 16.0 | approx. 80% | 4.5 | 4 x 50 | DIN 937 |
| M24 | 3.0 | 36.0 | 19.0 | approx. 79% | 5.5 | 5 x 63 | DIN 937 |

Product catalog

## Related Castle & Slotted Nuts products

[![Premium GB6181 304 Stainless Steel Slotted Round Castle Nut](https://img.engineeringhardware.com/Premium-GB6181-304-Stainless-Steel-Slotted-Round-Castle-Nut.webp)](https://engineeringhardware.com/product/premium-gb6181-304-stainless-steel-slotted-round-castle-nut/)

Slotted & Castle Nuts

### [Premium GB6181 304 Stainless Steel Slotted Round Castle Nut](https://engineeringhardware.com/product/premium-gb6181-304-stainless-steel-slotted-round-castle-nut/)

Hexagon Head · DIN, ISO

**US$0.14 – 0.24**MOQ 100 pieces

[![M30 M33 M36 Stainless Steel Hexagon Castle Nut](https://img.engineeringhardware.com/M30-M33-M36-Stainless-Steel-Hexagon-Castle-Nut.webp)](https://engineeringhardware.com/product/m30-m33-m36-stainless-steel-hexagon-castle-nut/)

Slotted & Castle Nuts

### [M30 M33 M36 Stainless Steel Hexagon Castle Nut](https://engineeringhardware.com/product/m30-m33-m36-stainless-steel-hexagon-castle-nut/)

Hexagon Head · DIN, ANSI, GB, JIS, GOST, BSW, ISO

**US$0.048 – 0.084**MOQ 1,000 pieces

[![Hot Selling Castle Nut Galvanized Slotted Stainless Steel M24 M20](https://img.engineeringhardware.com/Hot-Selling-Castle-Nut-Galvanized-Slotted-Stainless-Steel-M24-M20.webp)](https://engineeringhardware.com/product/hot-selling-castle-nut-galvanized-slotted-stainless-steel-m24-m20/)

Slotted & Castle Nuts

### [Hot Selling Castle Nut Galvanized Slotted Stainless Steel M24 M20](https://engineeringhardware.com/product/hot-selling-castle-nut-galvanized-slotted-stainless-steel-m24-m20/)

Square Head · DIN, ANSI, GB, BSW

**US$0.0012 – 0.60**MOQ 1 piece

[![Carbon Steel Hexgaon Head DIN935 DIN937 GB6180 ANSI B 18.2.2 Slotted Nut Castle Nut](https://img.engineeringhardware.com/Carbon-Steel-Hexgaon-Head-DIN935-DIN937-GB6180-ANSI-B-18-2-2-Slotted-Nut-Castle-Nut.webp)](https://engineeringhardware.com/product/carbon-steel-hexgaon-head-din935-din937-gb6180-ansi-b-18-2-2-slotted-nut-castle-nut/)

Slotted & Castle Nuts

### [Carbon Steel Hexgaon Head DIN935 DIN937 GB6180 ANSI B 18.2.2 Slotted Nut Castle Nut](https://engineeringhardware.com/product/carbon-steel-hexgaon-head-din935-din937-gb6180-ansi-b-18-2-2-slotted-nut-castle-nut/)

Hexagon Head · DIN, ANSI, GB, JIS, GOST, BSW, ISO Uni

**US$1,740 – 1,860**MOQ 3 tons

[![Hex Slot Castle Nut 316 304 Stainless Steel DIN935](https://img.engineeringhardware.com/Hex-Slot-Castle-Nut-316-304-Stainless-Steel-DIN935.webp)](https://engineeringhardware.com/product/hex-slot-castle-nut-316-304-stainless-steel-din935/)

Slotted & Castle Nuts

### [Hex Slot Castle Nut 316 304 Stainless Steel DIN935](https://engineeringhardware.com/product/hex-slot-castle-nut-316-304-stainless-steel-din935/)

Hexagon Head · DIN, ANSI, GB, JIS, GOST, BSW

**US$0.12**MOQ 1 piece

[![DIN935 M33 M24 Carbon Steel Roasting Galvanized High Quality Hexagon Slotted Nuts Flange Hex Castle Nut](https://img.engineeringhardware.com/DIN935-M33-M24-Carbon-Steel-Roasting-Galvanized-High-Quality-Hexagon-Slotted-Nuts-Flange-Hex-Castle-Nut.webp)](https://engineeringhardware.com/product/din935-m33-m24-carbon-steel-roasting-galvanized-high-quality-hexagon-slotted-nuts-2/)

Slotted & Castle Nuts

### [DIN935 M33 M24 Carbon Steel Roasting Galvanized High Quality Hexagon Slotted Nuts Flange Hex Castle Nut](https://engineeringhardware.com/product/din935-m33-m24-carbon-steel-roasting-galvanized-high-quality-hexagon-slotted-nuts-2/)

Hexagon Head · DIN, ANSI, GB, JIS, GOST, BSW

**US$0.0012 – 12.00**MOQ 100 pieces

[View all Slotted & Castle Nuts →](https://engineeringhardware.com/fastener-products/nuts/slotted-castle-nuts/) [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

Thin Castle Nuts are bought for a small number of well-defined jobs. These are the ones we ship them for. Stocked from M10 to M24.

### Industries that specify Thin Castle Nuts

- **Rail & heavy equipment:** Inspectable, positively locked joints.
- **Automotive chassis:** Wheel bearings, steering and suspension joints locked by a split pin.
- **Agricultural & plant:** Articulating joints not meant to be torqued solid.
- **Steel fabrication:** Bolted structural and frame connections.
- **Automotive & transport:** Vibration-prone joints where the locking type is specified on the drawing.
- **Maintenance & MRO:** Replacements matched to the existing bolt class, thread and finish.

### Typical applications

- tighten to torque, then back off to the nearest slot
- positive locking with a split pin through a cross-drilled bolt
- joints deliberately left free to articulate
- joints re-torqued at a service interval
- completing a bolted joint on a stud, rod or bolt
- locking an adjustment so it cannot drift

### 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.
- **High load:** Supplied in ISO 898-1 property classes, so the joint can be designed to a stated proof load and tightened to a calculated torque rather than by feel.
- **Match the class:** A nut below the bolt property class strips before the bolt reaches its own limit — pair class 8 nuts with 8.8 bolts, class 10 with 10.9.

[Full application guide: where Thin Castle Nuts are used, how to specify them, and the cases they are wrong for](https://engineeringhardware.com/applications/thin-castle-nuts-din-937/)

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

### Can I substitute DIN 937 for the corresponding DIN standard on a drawing?

On modern drawings the ISO standard is the master reference; the older DIN equivalent is a cross-reference. For most dimensional purposes the parts are interchangeable, but check tolerance grades and the head height — these are the most common points of divergence.

### Which edition of DIN 937 does this table follow?

The table reproduces the dimensions we supply thin castle nuts (din 937) to. We do not publish an edition year against it, so where the edition is contractually significant, cite the edition you require on the enquiry and we will confirm it against the table before quoting.

### How do I request a quotation?

Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day.

## Related Pages

[View the full Thin Castle Nuts (DIN 937) page](https://engineeringhardware.com/fastener/thin-castle-nuts-din-937/)