For torx and torx-plus screwdriver bits, DIN 3126 C is the governing document for the dimensions listed below. Mechanical and performance requirements for this part family are set by its own standards, not by the bolt and screw property-class documents.
DIN 3126 C — Scope
DIN 3126 C specifies the dimensional requirements for torx and torx-plus screwdriver bits.
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 torx and torx-plus screwdriver bits 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 C
| Bit | Drive | Typical mating screw | Service |
|---|---|---|---|
| T10 | Torx | M3 hexalobular | electronics, appliance |
| T15 | Torx | M3.5 hexalobular | appliance, light assembly |
| T20 | Torx | M4 hexalobular | general assembly |
| T25 | Torx | M5 hexalobular | decking, general assembly |
| T27 | Torx | M5 u2013 M6 hexalobular | construction screws |
| T30 | Torx | M6 hexalobular | structural timber screws |
| T40 | Torx | M8 hexalobular | heavy assembly |
| T20 IP | Torx security (pin-in) | M4 tamper-resistant | public and outdoor equipment |
| T25 IP | Torx security (pin-in) | M5 tamper-resistant | public and outdoor equipment |
Equivalent Standards
Where direct equivalents exist (ISO ↔ DIN, ISO ↔ ASME), they are listed on the parent Torx and Torx-Plus Screwdriver Bits page.
Always confirm against the dimensions on this page, since some "equivalent" standards differ in tolerances and head geometry.
When to Specify DIN 3126 C
DIN 3126 C is still widely used in European mechanical engineering and as a cross-reference on legacy drawings; its ISO equivalent is preferred for new designs.
