DIN 3126 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.
DIN 3126 — Scope
DIN 3126 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 DIN 3126
| 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
DIN 3126 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 DIN 3126
DIN 3126 is still widely used in European mechanical engineering and as a cross-reference on legacy drawings; its ISO equivalent is preferred for new designs.
