ST threads, standardized under DIN 7970, are self-tapping screw threads designed specifically for sheet metal applications. These threads enable screws to cut their own mating threads into thin sheet materials such as steel, aluminum, and plastic without requiring pre-threaded holes.
ST threads feature a sharply angled profile, often 60° or 45°, and a narrow root diameter, which enhances their ability to penetrate and secure into sheet metal efficiently. They are widely used in automotive, construction, and electronics where lightweight and secure fastening is required.
Key Characteristics: ✔ Thread Profile: Sharp-edged, self-tapping design
✔ No Pre-Threading Required: Screws form their own threads in material
✔ High Holding Strength: Designed for secure fastening in thin sheets
✔ Common Uses: Sheet metal assemblies, electrical enclosures, automotive applications
✔ Standardization: Defined under DIN 7970
Key Features of ST Threads
✔ Self-Tapping Capability – No need for pre-threaded holes
✔ High Resistance to Loosening – Secure grip in thin materials
✔ Sharp Cutting Edge – Optimized for efficient penetration
✔ Available in Different Head Styles – Flat, pan, and hex heads for various applications
✔ Commonly Used in Lightweight Assemblies
ST Threads vs. Conventional Machine Threads
| Feature | ST Threads (DIN 7970) | Machine Threads (ISO Metric) |
|---|---|---|
| Thread Angle | 60° or 45° | 60° |
| Self-Tapping | Yes | No |
| Pre-Tapped Hole Required? | No | Yes |
| Holding Strength | High in thin sheets | High in pre-threaded materials |
| Common Use | Sheet metal fastening | Pre-threaded holes |
ST Thread Dimensions (DIN 7970)
The following table provides standard ST thread dimensions:
| Designation | Major Diameter (mm) | Pitch (mm) | Thread Angle (°) |
| ST 2.2 | 2.20 | 0.80 | 60° |
| ST 2.9 | 2.90 | 1.10 | 60° |
| ST 3.5 | 3.50 | 1.30 | 60° |
| ST 4.2 | 4.20 | 1.40 | 60° |
| ST 4.8 | 4.80 | 1.60 | 60° |
| ST 5.5 | 5.50 | 1.80 | 60° |
| ST 6.3 | 6.30 | 1.80 | 60° |
Common Applications of ST Threads
- Automotive Industry – Fastening sheet metal components
- Electrical Enclosures – Secure assembly of metal casings
- Aerospace Applications – Lightweight but strong fastenings
- HVAC Systems – Fastening sheet metal ducts and vents
- Furniture and Appliances – Assembling lightweight metal structures
Related Thread Standards
- ISO 2901 – General Trapezoidal Thread Specifications
- DIN 103 – German Standard for Trapezoidal Threads
- ANSI B1.5 – Acme Threads (North American equivalent)
Important Notice on Standards Validity
This information is for reference purposes only. Users should consult official sources and updated standards to ensure compliance with current regulations. The validity of standards may change over time, so it is recommended to verify them through recognized engineering and standardization organizations (ISO, DIN, ANSI, etc.).
Check with relevant standardization bodies in your region to confirm whether a specific standard is still valid and applicable. Regulations and industry requirements may vary based on region and application.