ISO 14581 specifies the dimensions and tolerances for torx countersunk machine screws. The full dimensional table is reproduced below, followed by the DIN, ISO and ASME parts that match or supersede it.
- Standard
- ISO 14581
- Product
- Torx Countersunk Machine Screws
- Governing standards
- ISO 14581
Equivalence between national standards is dimensional, not always metallurgical. Check the property class separately when substituting.
The table below lists the dimensions catalogued for torx countersunk machine screws under ISO 14581. The scope of ISO 14581 itself is not summarised here — where a figure matters, confirm it against the published document.
ISO 14581 — Scope
The table below lists the dimensions catalogued for torx countersunk machine screws under ISO 14581. The scope of ISO 14581 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 14581. Tolerances for this part are the limits shown against each dimension in the table.
Dimensions Specified by ISO 14581
| Thread size | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Drive size | Max torque (Nm, typical) | Common length range (mm) | Reference standard |
|---|
| M3 | 0.5 | 5.6 | 1.65 | T10 | 2.0 | 6~30 | ISO 14581 |
| M4 | 0.7 | 7.5 | 2.20 | T20 | 4.5 | 8~40 | ISO 14581 |
| M5 | 0.8 | 9.2 | 2.50 | T25 | 9.0 | 8~50 | ISO 14581 |
| M6 | 1.0 | 11.0 | 3.00 | T30 | 15.0 | 10~60 | ISO 14581 |
| M8 | 1.25 | 14.5 | 4.00 | T40 | 36.0 | 12~80 | ISO 14581 |
| M10 | 1.5 | 18.0 | 5.00 | T50 | 70.0 | 16~100 | ISO 14581 |
Companion Standards
A complete specification for torx countersunk machine screws normally cites several documents: one for the geometry, one for the material or mechanical properties, and one for the finish. ISO 14581 is one of them, not all of them.
When to Specify ISO 14581
Choose ISO 14581 for international engineering work and OEM supply where ISO standards are the contractual reference. It is the default modern specification for torx countersunk machine screws.
Custom manufacturing · Made to drawing
Need a screw to this standard in a non-standard size?
Parts built to ISO 14581 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. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
Custom screw manufacturingSend a drawing
Applications & Industries
Where Torx Countersunk Machine Screws are used, and what decides the specification in each case. Stocked from M3 to M10.
Industries that specify Torx Countersunk Machine Screws
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Automotive assembly
The default drive on most modern vehicle assembly.
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Automated assembly
Robot and driver lines where cam-out costs cycle time.
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Electronics & appliances
Small screws driven to a controlled torque.
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Steel fabrication
Bolted connections in frames, enclosures, walkways and weldments, on the bench and on site.
-
Energy & infrastructure
Tower, pipework, switchgear and plant fixings specified for long service life and inspectable joints.
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Maintenance & MRO
Stocked replacements matched to an existing property class, thread and finish.
Typical applications
- roughly twice the torque of a Phillips of the same size
- transmitting torque with no axial cam-out component
- driving without down-force, so a robot arm can hold position
- clamping two machined faces to a calculated preload
- bolting brackets, motors and gearboxes to a frame
- assemblies that are dismantled for service and re-torqued
Service conditions to specify against
- Marine and coastal
- Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
- High load
- Supplied in ISO 898-1 property classes, so the joint can be designed to a stated proof load and tightened to a calculated torque rather than by feel.
- Torque and preload
- The joint is designed around bolt tension, so lubrication, coating and the friction coefficient all change the torque figure — state them together.
Where to use something else
- Do not use a machine thread into unthreaded sheet or timber; use a tapping screw, rivet nut or insert made for that parent material.
Full application guide: where Torx Countersunk Machine Screws are used, how to specify them, and the cases they are wrong for
