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
ISO 1173 specifies the dimensional requirements for magnetic bit holders and extensions.
Material, surface condition and any performance rating are set by separate documents specific to this part family — ISO 898-1 and ISO 898-2, which govern bolt and nut property classes, do not apply here.
Tolerance & Product Grades
Tolerances for magnetic bit holders and extensions are given as limits on the individual dimensions in the table rather than as a fastener product grade.
Where a general-tolerance class is cited on the drawing instead, it applies to the dimensions not otherwise toleranced.
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
ISO 1173 controls only the geometry of magnetic bit holders and extensions. Surface finish is governed by separate finish standards (for example ISO 4042 for electroplating), and corrosion testing by ISO 9227 (neutral salt spray). Mechanical performance is set by the standards specific to this part family, not by ISO 898-1 or ISO 898-2, which apply to bolts, screws and nuts.
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.
