---
title: "ISO 1173 Magnetic Bit Holders and Extensions Specification"
description: "ISO 1173 Magnetic Bit Holders and Extensions: full dimensional table with tolerances. DIN, ISO and ASME equivalents listed side by side."
url: https://engineeringhardware.com/guide/standard/iso-1173-cross-recess-screwdriver-bits/
source: Engineering Hardware & Fasteners
---

# ISO 1173 Magnetic Bit Holders and Extensions Specification

Tools · DIN 3126 / ISO 1173 (C6.3 hexagon drive)

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

ISO 1173 specifies the dimensions and tolerances for magnetic bit holders and extensions. The full dimensional table is reproduced below, followed by the DIN, ISO and ASME parts that match or supersede it.

- **Standard:** ISO 1173
- **Product:** Magnetic Bit Holders and Extensions
- **Governing standards:** DIN 3126 / ISO 1173 (C6.3 hexagon drive)

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

![ISO 1173 Magnetic Bit Holders and Extensions Specification reference image](https://engineeringhardware.com/wp-content/uploads/2026/09/Magnetic-Bit-Holders.webp)

ISO 1173 is the standard cited for magnetic bit holders and extensions. This page sets out what the standard controls for this part, reproduces the dimensional table supplied against it, and notes the related designations referenced on drawings.

## ISO 1173 — Scope

The table below lists the dimensions catalogued for magnetic bit holders and extensions under ISO 1173. The scope of ISO 1173 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 ISO 1173. Tolerances for this part are the limits shown against each dimension in the table.

## Dimensions Specified by ISO 1173

| Form | Drive | Typical length | Retention |
| --- | --- | --- | --- |
| magnetic bit holder | 1/4 in hex shank, C6.3 socket | 60 mm | magnet |
| magnetic bit holder | 1/4 in hex shank, C6.3 socket | 150 mm | magnet |
| quick-release bit holder | 1/4 in hex shank, C6.3 socket | 75 mm | ball detent, sprung sleeve |
| bit extension bar | 1/4 in hex shank, C6.3 socket | 300 mm | magnet |
| square-drive bit adaptor | 3/8 in square to C6.3 | 50 mm | ball detent |

## Companion Standards

A complete specification for magnetic bit holders and extensions normally cites several documents: one for the geometry, one for the material or mechanical properties, and one for the finish. ISO 1173 is one of them, not all of them.

## When to Specify ISO 1173

Choose ISO 1173 for international engineering work and OEM supply where ISO standards are the contractual reference. It is the default modern specification for magnetic bit holders and extensions.

Custom manufacturing · Made to drawing

## Need a fastener tool to this standard in a non-standard size?

Parts built to ISO 1173 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.

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

[Custom fastener tool manufacturing](https://engineeringhardware.com/custom/tools/)[Send a drawing](https://engineeringhardware.com/custom/tools/#rfq)

## Technical Drawing

Dimensioned line drawing of magnetic bit holder Magnetic Bit Holders and Extensions to DIN 3126 / ISO 1173 (C6.3 hexagon drive). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.

- **Drive:** 1/4 in hex shank, C6.3 socket
- **Typical length:** 60 mm
- **Retention:** magnet

## Dimensions & Specifications (DIN 3126 / ISO 1173 (C6.3 hexagon drive))

| Form | Drive | Typical length | Retention |
| --- | --- | --- | --- |
| magnetic bit holder | 1/4 in hex shank, C6.3 socket | 60 mm | magnet |
| magnetic bit holder | 1/4 in hex shank, C6.3 socket | 150 mm | magnet |
| quick-release bit holder | 1/4 in hex shank, C6.3 socket | 75 mm | ball detent, sprung sleeve |
| bit extension bar | 1/4 in hex shank, C6.3 socket | 300 mm | magnet |
| square-drive bit adaptor | 3/8 in square to C6.3 | 50 mm | ball detent |

Product catalog

## Related Bit Sockets & Holders products

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Socket Head Cap & Allen Screws

### [Non-Knurling Stainless Steel Hex Socket Cap Head Screw DIN912](https://engineeringhardware.com/product/non-knurling-stainless-steel-hex-socket-cap-head-screw-din912/)

Cap Head · DIN

**US$0.012 – 6.00**MOQ 1,000 pieces

[![DIN7991 Stainless Steel Flat Hexagon Socket Head Screw Machine Screw](https://img.engineeringhardware.com/DIN7991-Stainless-Steel-Flat-Hexagon-Socket-Head-Screw-Machine-Screw.webp)](https://engineeringhardware.com/product/din7991-stainless-steel-flat-hexagon-socket-head-screw-machine-screw/)

Socket Head Cap & Allen Screws

### [DIN7991 Stainless Steel Flat Hexagon Socket Head Screw Machine Screw](https://engineeringhardware.com/product/din7991-stainless-steel-flat-hexagon-socket-head-screw-machine-screw/)

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

**US$0.0019 – 2.40**MOQ 1,000 pieces

[![DIN7991 White Blue Zinc Brass Black Oxide Hex Socket Countersunk Cap Screws](https://img.engineeringhardware.com/DIN7991-White-Blue-Zinc-Brass-Black-Oxide-Hex-Socket-Countersunk-Cap-Screws.webp)](https://engineeringhardware.com/product/din7991-white-blue-zinc-brass-black-oxide-hex-socket-countersunk-cap-screws/)

Socket Head Cap & Allen Screws

### [DIN7991 White Blue Zinc Brass Black Oxide Hex Socket Countersunk Cap Screws](https://engineeringhardware.com/product/din7991-white-blue-zinc-brass-black-oxide-hex-socket-countersunk-cap-screws/)

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

**US$0.0012 – 0.12**MOQ 1 piece

[![304 Stainless Steel Hollow Core Low-Profile Socket Head Screws – DIN7984 Standard, Hollow Design for Ventilation](https://img.engineeringhardware.com/304-Stainless-Steel-Hollow-Core-Low-Profile-Socket-Head-Screws-DIN7984-Standard-Hollow-Design-for-Ventilation.webp)](https://engineeringhardware.com/product/304-stainless-steel-hollow-core-low-profile-socket-head-screws-a-din7984-standard/)

Socket Head Cap & Allen Screws

### [304 Stainless Steel Hollow Core Low-Profile Socket Head Screws – DIN7984 Standard, Hollow Design for Ventilation](https://engineeringhardware.com/product/304-stainless-steel-hollow-core-low-profile-socket-head-screws-a-din7984-standard/)

Round Head · DIN, ANSI, GB, JIS, BSW

**US$0.012**MOQ 1,000 pieces

[![Stainless Steel DIN7991 Hex Socket Countersunk Head Cap Screw](https://img.engineeringhardware.com/Stainless-Steel-DIN7991-Hex-Socket-Countersunk-Head-Cap-Screw.webp)](https://engineeringhardware.com/product/stainless-steel-din7991-hex-socket-countersunk-head-cap-screw/)

Socket Head Cap & Allen Screws

### [Stainless Steel DIN7991 Hex Socket Countersunk Head Cap Screw](https://engineeringhardware.com/product/stainless-steel-din7991-hex-socket-countersunk-head-cap-screw/)

Hexagon Head · DIN, ANSI, ISO

**US$0.29 – 0.34**MOQ 100 pieces

[![Hexagon Socket Head Shoulder Screws](https://img.engineeringhardware.com/Hexagon-Socket-Head-Shoulder-Screws.webp)](https://engineeringhardware.com/product/hexagon-socket-head-shoulder-screws/)

Socket Head Cap & Allen Screws

### [Hexagon Socket Head Shoulder Screws](https://engineeringhardware.com/product/hexagon-socket-head-shoulder-screws/)

Round Head · DIN, Non-Standard

**US$1.20 – 36.00**MOQ 100,000 pieces

[View all Socket Head Cap & Allen Screws →](https://engineeringhardware.com/fastener-products/screws/socket-head-cap-allen-screws/) [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

The sectors that buy Magnetic Bit Holders and Extensions to DIN 3126 / ISO 1173 (C6.3 hexagon drive), and the duty each one buys them for. Stocked from magnetic bit holder to square-drive bit adaptor (size designation).

### Industries that specify Magnetic Bit Holders and Extensions

- **Cabinet and shopfitting:** One-handed screw starting.
- **Electrical work:** Deep back boxes.
- **General assembly:** Fast bit changes.
- **Site installation:** Reaching recessed fixings.
- **Assembly & maintenance:** Installing and servicing the fasteners in this catalog.

### Typical applications

- using the quick-release sleeve where bits change often
- relying on the magnet to start a screw one-handed
- checking the holder is rated for impact use
- choosing the length by how deep the recess is
- driving and releasing fasteners on the bench and in the field

### Where to use something else

- Do not use a long extension at an angle on a high-torque screw; the shank flexes and the bit walks out of the recess.

[Full application guide: where Magnetic Bit Holders and Extensions are used, how to specify them, and the cases they are wrong for](https://engineeringhardware.com/applications/magnetic-bit-holders/)

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 edition of ISO 1173 does this table follow?

The table reproduces the dimensions we supply magnetic bit holders and extensions 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.

### Can I substitute ISO 1173 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 Magnetic Bit Holders and Extensions page](https://engineeringhardware.com/fastener/magnetic-bit-holders/)

### More Magnetic Bit Holders and Extensions Guides