Buttress threads are asymmetrical thread profiles designed for applications where high loads are applied in one direction. These threads provide high axial load capacity while minimizing friction and wear in the primary loading direction.
Unlike symmetrical threads such as Acme or trapezoidal threads, Buttress threads have an angled leading flank (usually 30°) and a nearly vertical trailing flank (usually 3° to 7°). This design allows for efficient force transmission while preventing backlash and reducing stress concentrations.
Buttress threads are standardized under ISO 2904 and DIN 513, making them widely used in heavy-duty applications, such as presses, hydraulic systems, and oilfield equipment.
Key Characteristics: ✔ Thread Profile: Asymmetrical with a steep pressure flank
✔ Load-Bearing Direction: Optimized for force transmission in one direction
✔ High Efficiency: Reduces friction losses compared to trapezoidal and Acme threads
✔ Common Uses: Presses, injection molding machines, and oil drilling equipment
✔ Standardization: Defined under ISO 2904 (International) and DIN 513 (German Standard)
Key Features of Buttress Threads
✔ Designed for High Axial Loads acting in one direction
✔ Low Backlash and High Strength due to steep pressure flank
✔ Reduces Wear and Tear compared to symmetrical thread profiles
✔ More Efficient Force Transmission in heavy-duty machinery
✔ Used in Linear Motion Applications such as hydraulic cylinders and lead screws
Buttress Threads vs. Acme & Trapezoidal Threads
| Feature | Buttress Threads (ISO 2904) | Acme Threads (ANSI B1.5) | Trapezoidal Threads (ISO 2901) |
|---|---|---|---|
| Thread Angle | 30° (leading) / 3°-7° (trailing) | 29° | 30° |
| Profile Shape | Asymmetrical | Symmetrical | Symmetrical |
| Load Capacity | High (one direction) | Moderate (both directions) | Moderate (both directions) |
| Friction | Low | Higher | Moderate |
| Backlash | Minimal | Present | Present |
| Common Use | Heavy-duty pressing, oil drilling | Lead screws, motion control | Lead screws, motion control |
Buttress Thread Dimensions (ISO 2904, DIN 513)
The following table provides standard Buttress thread dimensions:
| Nominal Size | Major Diameter (mm) | Pitch Diameter (mm) | Minor Diameter (mm) | Pitch (mm) |
| B 10×2 | 10.00 | 9.10 | 8.20 | 2.0 |
| B 16×3 | 16.00 | 14.85 | 13.70 | 3.0 |
| B 20×4 | 20.00 | 18.70 | 17.40 | 4.0 |
| B 25×5 | 25.00 | 23.55 | 22.10 | 5.0 |
| B 32×6 | 32.00 | 30.40 | 28.80 | 6.0 |
| B 40×8 | 40.00 | 38.00 | 36.00 | 8.0 |
Common Applications of Buttress Threads
- Hydraulic & Pneumatic Cylinders requiring unidirectional load transmission
- Injection Molding Machines for plastic and metal forming
- Oil Drilling Equipment (casing and tubing connections)
- Press Screws & Heavy-Duty Jacks where high force is applied in one direction
- Structural Applications such as bridge tensioning rods
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.