ISO 6789 is the standard cited for torque wrenches for fastener tightening. 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 6789 — Scope
ISO 6789 specifies the dimensional requirements for torque wrenches for fastener tightening.
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 torque wrenches for fastener tightening 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 6789
| Range | Square drive | Typical bolt size at mid-range | Class |
|---|---|---|---|
| 1 u2013 6 Nu00b7m | 1/4 in | M3 u2013 M4 | ISO 6789 click type |
| 5 u2013 25 Nu00b7m | 3/8 in | M5 u2013 M6 | ISO 6789 click type |
| 20 u2013 100 Nu00b7m | 1/2 in | M8 u2013 M10 | ISO 6789 click type |
| 40 u2013 200 Nu00b7m | 1/2 in | M10 u2013 M14 | ISO 6789 click type |
| 70 u2013 350 Nu00b7m | 3/4 in | M16 u2013 M20 | ISO 6789 click type |
| 150 u2013 750 Nu00b7m | 3/4 in | M20 u2013 M24 | ISO 6789 click type |
Companion Standards
ISO 6789 controls only the geometry of torque wrenches for fastener tightening. 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 6789
Choose ISO 6789 for international engineering work and OEM supply where ISO standards are the contractual reference. It is the default modern specification for torque wrenches for fastener tightening.
