---
title: "DIN 7991 Drilled-Head Capstan Sealing Screws Specification"
description: "DIN 7991 Drilled-Head Capstan Sealing Screws: full dimensional table with tolerances. DIN, ISO and ASME equivalents listed side by side."
url: https://engineeringhardware.com/guide/standard/din-7991-countersunk-socket-screws/
source: Engineering Hardware & Fasteners
---

# DIN 7991 Drilled-Head Capstan Sealing Screws Specification

Screws · GB/T 70.1 / DIN 912 / ISO 4762 and GB/T 70.3 / DIN 7991 / ISO 10642

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

DIN 7991 specifies the dimensions and tolerances for drilled-head capstan sealing screws. The full dimensional table is reproduced below, followed by the DIN, ISO and ASME parts that match or supersede it.

- **Standard:** DIN 7991
- **Product:** Drilled-Head Capstan Sealing Screws
- **Governing standards:** GB/T 70.1 / DIN 912 / ISO 4762 and GB/T 70.3 / DIN 7991 / ISO 10642

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

![DIN 7991 Drilled-Head Capstan Sealing Screws Specification reference image](https://engineeringhardware.com/wp-content/uploads/2026/09/Drilled-Head-Capstan-Sealing-Meter-Screws.webp)

DIN 7991 is the governing dimensional standard for drilled-head capstan sealing screws. This page sets out the scope of the standard, reproduces the full size table it specifies, and lists the DIN/ISO/ASME cross-references commonly cited in datasheets and drawings.

## DIN 7991 — Scope

DIN 7991 is "Hexagon socket countersunk head screws". Its ISO counterpart is ISO 10642.

Material, property class, surface finish and packaging are governed by separate documents — ISO 898-1 and ISO 898-2 for mechanical property classes, ISO 4042 for electroplated finishes.

## Tolerance & Product Grades

DIN 7991 does not divide drilled-head capstan sealing screws into product grades. Tolerances are given as limits on the individual dimensions in the table.

Where a general-tolerance class is cited on the drawing instead, it applies to the dimensions not otherwise toleranced.

## Dimensions Specified by DIN 7991

| Head form | Governing standards | Sealing feature | Property class | Finish |
| --- | --- | --- | --- | --- |
| hexagon socket head cap | GB/T 70.1-2008 / DIN 912 / ISO 4762 | cross-drilled head for sealing wire | 8.8 | black oxide |
| countersunk hexagon socket | GB/T 70.3-2008 / DIN 7991 / ISO 10642 | cross-drilled head for sealing wire | 8.8 | black oxide |

## Companion Standards

DIN 7991 controls only the geometry of drilled-head capstan sealing screws. The mechanical strength is set by ISO 898-1 (bolts, screws and studs) or ISO 898-2 (nuts); the surface finish is governed by separate finish standards such as ISO 4042 for electroplating. For corrosion testing, the relevant document is ISO 9227 (neutral salt spray).

## When to Specify DIN 7991

DIN 7991 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 screw to this standard in a non-standard size?

Parts built to DIN 7991 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 warm forging.

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

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

## Technical Drawing

Dimensioned line drawing of hexagon socket head cap Drilled-Head Capstan Sealing Screws to GB/T 70.1 / DIN 912 / ISO 4762 and GB/T 70.3 / DIN 7991 / ISO 10642. Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

- **Governing standards:** GB/T 70.1-2008 / DIN 912 / ISO 4762
- **Sealing feature:** cross-drilled head for sealing wire
- **Property class:** 8.8
- **Finish:** black oxide

## Dimensions & Specifications (GB/T 70.1 / DIN 912 / ISO 4762 and GB/T 70.3 / DIN 7991 / ISO 10642)

| Head form | Governing standards | Sealing feature | Property class | Finish |
| --- | --- | --- | --- | --- |
| hexagon socket head cap | GB/T 70.1-2008 / DIN 912 / ISO 4762 | cross-drilled head for sealing wire | 8.8 | black oxide |
| countersunk hexagon socket | GB/T 70.3-2008 / DIN 7991 / ISO 10642 | cross-drilled head for sealing wire | 8.8 | black oxide |

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## 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

Drilled-Head Capstan Sealing Screws are bought for a small number of well-defined jobs. These are the ones we ship them for. Stocked from hexagon socket head cap to countersunk hexagon socket (nominal diameter).

### Industries that specify Drilled-Head Capstan Sealing Screws

- **Regulated installations:** Evidence of an unbroken seal on inspection.
- **Utility metering:** A cross-drilled head takes a sealing wire that shows tampering.
- **Instrument enclosures:** Closure control on calibrated equipment.
- **Test and measurement:** Sealed access for certified instruments.
- **Food, pharma & cleanroom:** Stainless assemblies that are washed down, where the finish matters as much as the strength.
- **Machine building & OEM:** The default fastener on production equipment: covers, brackets, motor mounts and sub-assemblies tightened to a specified torque.

### Typical applications

- recording the seal number against the installation
- threading a sealing wire through the drilled head and crimping it
- choosing the cap or countersunk form for the enclosure detail
- specifying class 8.8 black oxide as listed
- joints where the property class is stated on the drawing
- clamping two machined faces to a calculated preload

### 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.
- **Sealed joints:** Used where the fixing has to keep water or air out as well as hold — the elastomer, not the fastener, decides service life.
- **Torque and preload:** The joint is designed around bolt tension, so lubrication, coating and the friction coefficient all change the torque figure — state them together.

### Where to use something else

- Do not fit a sealing screw without actually closing the wire; an undrawn seal proves nothing.
- Do not use a machine thread into unthreaded sheet or timber; use a tapping screw, rivet nut or insert made for that parent material.

[Full application guide: where Drilled-Head Capstan Sealing Screws are used, how to specify them, and the cases they are wrong for](https://engineeringhardware.com/applications/drilled-head-capstan-sealing-screws/)

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

### What is DIN 7991?

DIN 7991 is "Hexagon socket countersunk head screws". Its ISO counterpart is ISO 10642.

### What does DIN 7991 specify for Drilled-Head Capstan Sealing Screws?

DIN 7991 specifies the dimensions and tolerances of drilled-head capstan sealing screws. Material and property class are governed by separate documents.

### Does DIN 7991 specify the mechanical strength?

No. DIN 7991 controls only the geometry of drilled-head capstan sealing screws. The mechanical strength is set by ISO 898-1 (bolts, screws and studs) or ISO 898-2 (nuts), and the finish by separate documents.

### Can I substitute DIN 7991 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.

### 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 Drilled-Head Capstan Sealing Screws page](https://engineeringhardware.com/fastener/drilled-head-capstan-sealing-screws/)

### More Drilled-Head Capstan Sealing Screws Guides