ISO 10666 Mechanical Property of Self-Drilling Screws
ISO 10666 specifies the mechanical and functional properties of heat-treated drilling screws with tapping screw threads in accordance with ISO 1478. It establishes requirements to ensure that these screws can drill their own core holes and form mating threads without unacceptable deformation or fracture under the specified test conditions.
The standard focuses on three key aspects of screw performance: surface hardness, drilling and thread-forming capability, and torsional strength. These requirements provide a basis for evaluating the screw’s ability to penetrate the specified substrate, form a functional mating thread and withstand the torque applied during installation.
Material Requirements
ISO 10666 specifies that drilling screws shall be manufactured from case-hardening steel or heat-treatable steel. These materials allow the screws to achieve the required hardness and metallurgical properties after heat treatment, providing a hard surface for drilling and thread forming while maintaining adequate core strength and toughness.
Hardness
| Hardness Property | Requirement | Test Method | Minimum Tempering Temperature |
|---|---|---|---|
| Surface Hardness | Min.530HV 0.3 | Vickers Hardness Test | 330℃ |
| Core Hardness | 320-400 HV 5 or HV10 | Vickers Hardness Test | 330℃ |
Case Depth
| Thread | Case Depth(min) | Case Depth(max) |
|---|---|---|
| ST 2.9 and ST 3.5 | 0.05 | 0.18 |
| ST 4.2 to ST 5.5 | 0.1 | 0.23 |
| ST 6.3 | 0.15 | 0.28 |
Test Data for the Drilling and Screwing
| Thread | Thickness of test plate (mm) | Axial force (N) | Test duration max. (s) | Rotational speed of screw under load (min⁻¹) |
|---|---|---|---|---|
| ST 2.9 | 0.7 + 0.7 = 1.4 | 150 | 3 | 1800 to 2500 |
| ST 3.5 | 1 + 1 = 2 | 150 | 4 | 1800 to 2500 |
| ST 4.2 | 1.5 + 1.5 = 3 | 250 | 5 | 1800 to 2500 |
| ST 4.8 | 2 + 2 = 4 | 250 | 7 | 1800 to 2500 |
| ST 5.5 | 2 + 3 = 5 | 350 | 11 | 1000 to 1800 |
| ST 6.3 | 2 + 3 = 5 | 350 | 13 | 1000 to 1800 |
Test data for the drilled hole
| Thread | Plate thickness (mm) | Hole diameter min. (mm) | Hole diameter max. (mm) |
|---|---|---|---|
| ST 2.9 | 1 | 2.2 | 2.5 |
| ST 3.5 | 1 | 2.7 | 3.0 |
| ST 4.2 | 2 | 3.2 | 3.6 |
| ST 4.8 | 2 | 3.7 | 4.2 |
| ST 5.5 | 2 | 4.2 | 4.8 |
| ST 6.3 | 2 | 4.8 | 5.4 |
Minimum torsional strength
| Thread | Minimum torsional strength (N·m) |
|---|---|
| ST 2.9 | 1.5 |
| ST 3.5 | 2.8 |
| ST 4.2 | 4.7 |
| ST 4.8 | 6.9 |
| ST 5.5 | 10.4 |
| ST 6.3 | 16.9 |