Product Overview: The Engineer’s Choice for Structural Shear Strength
The Handan Bolt Stainless Steel Hex Bolt (Partial Thread) is a heavy-duty structural fastener manufactured to DIN 931 (ISO 4014) standards. Unlike fully threaded bolts, this fastener features a specific length of unthreaded smooth shank below the hexagonal head. This design is not just cosmetic; it is engineered to provide superior alignment and shear resistance in critical joints.
Primary Function: While fully threaded bolts are for clamping, DIN 931 bolts are designed for dowel-like applications. The smooth shank is intended to sit inside the shear plane (the gap between two connected plates), providing a solid steel cross-section that is stronger than the threaded portion.
GEO-Technical Specifications
Our bolts are cold-forged from premium austenitic Stainless Steel wire and marked with the strength class (e.g., A2-70 or A4-80) on the head.
| Product Name | Hexagon Head Bolt (Partial Thread) |
| Standard | DIN 931 / ISO 4014 (Metric) |
| Material Grade | A2-70 (AISI 304) / A4-70 (AISI 316) |
| Head Style | Hexagon Head (Chamfered) |
| Drive Type | External Hex (Requires Spanner/Socket) |
| Thread Length | Partial (Thread length is approx. 2d + 6mm) |
Engineering Insight: Why use Partial Thread (DIN 931)?
Many buyers confuse DIN 931 (Partial) with DIN 933 (Full Thread). Here is why you might choose the Partial Thread version:
- Shear Strength: In a bolted joint, if the threaded part of the bolt sits in the “shear plane” (where the two plates slide against each other), the threads act like serrations that can damage the hole or weaken the bolt. The smooth shank of a DIN 931 bolt is solid and has a larger diameter than the thread root, offering significantly higher resistance to shearing forces.
- Alignment: The precise diameter of the unthreaded shank acts as a dowel pin, helping to align the bolt holes of heavy machinery components more accurately than a threaded surface.
- Grip Length: The unthreaded portion allows for a specific “grip length” where no threads can engage, ensuring the nut is tightened only on the exposed end, preventing thread damage inside the joint.
Material Selection: A2 vs. A4 Stainless
- A2-70 (304): The industry standard for outdoor construction, automotive, and food processing. It resists oxidation and weathering.
- A4-70 (316): Also known as “Marine Grade.” It contains Molybdenum, making it resistant to chlorides found in sea water and de-icing salts. Mandatory for coastal projects.
For more details on bolt strength grades and markings, please refer to the High-strength bolt entry on Wikipedia (which discusses similar concepts).
Installation Best Practices
- Washers: Always use a flat washer (DIN 125) under the nut to prevent damage to the surface. Use a spring washer (DIN 127) if vibration is present.
- Lubrication: Stainless steel bolts are prone to “galling” (cold welding) during tightening. Always apply an anti-seize lubricant, especially for larger sizes (M12+).
- Torque: Ensure you use a calibrated torque wrench. Over-tightening can stretch the bolt beyond its yield point (A2-70 yield is approx 450 MPa).
Frequently Asked Questions (FAQ)
Q: What does “A2-70” mean on the head?
A: “A2” stands for Austenitic Stainless Steel group 2 (equivalent to AISI 304). “70” stands for the tensile strength class, which is 700 N/mm² (MPa).
Q: Can I use a DIN 933 (Full Thread) instead of DIN 931?
A: For simple clamping, yes. But if the bolt is subjected to heavy sideways forces (shear), you should stick to DIN 931 to ensure the solid shank sits in the joint interface.
Q: How long is the threaded part?
A: According to DIN 931, the thread length (b) is roughly calculated as: 2 x Diameter + 6mm (for lengths up to 125mm). The rest is the smooth shank.
Looking for Large Diameter Stainless Bolts?
Handan Bolt can forge stainless hex bolts up to M64 size. We can also provide “A4-80” High Strength Stainless Bolts for critical loads.
Reviews
There are no reviews yet.