ISO 4017 and DIN 933 both specify hexagon head bolts with full thread, but they differ in dimensional tolerances and thread length. For engineers selecting fasteners, understanding these differences is critical for ensuring proper fit and load distribution.
Key Differences Between ISO 4017 and DIN 933
The primary distinction lies in the thread length and the width across flats (WAF). DIN 933 has a slightly shorter thread length for certain diameters, while ISO 4017 standardizes thread length to be full thread (thread length approximately 2d + 6 mm for d ≤ 125 mm). Additionally, ISO 4017 adopts metric coarse thread per ISO 261, whereas DIN 933 originally used metric coarse thread per DIN 13.
Thread Length Comparison
For M10 bolts, DIN 933 specifies a thread length of 26 mm, while ISO 4017 requires 26 mm as well (full thread). However, for larger diameters like M20, DIN 933 has a thread length of 46 mm, whereas ISO 4017 specifies 46 mm (full thread). The difference becomes negligible for most sizes, but engineers should verify for critical applications.
Width Across Flats (WAF)
DIN 933 uses the same WAF as ISO 4017 for most sizes, but some older DIN standards had different WAF for certain diameters. For example, M10 hex bolts under DIN 933 have a WAF of 17 mm, which matches ISO 4017. However, for M12, DIN 933 WAF is 19 mm, while ISO 4017 also specifies 19 mm. No significant deviation exists for common sizes.
Material and Property Classes
Both standards allow the same material grades and property classes. Common property classes include:
- 4.6: Low carbon steel, tensile strength 400 MPa, yield strength 240 MPa.
- 8.8: Medium carbon steel, quenched and tempered, tensile strength 800 MPa, yield strength 640 MPa.
- 10.9: Alloy steel, quenched and tempered, tensile strength 1000 MPa, yield strength 900 MPa.
- A2-70: Stainless steel A2 (304), tensile strength 700 MPa.
- A4-80: Stainless steel A4 (316), tensile strength 800 MPa.
Dimensional Comparison Table
| Thread Size | DIN 933 Thread Length (mm) | ISO 4017 Thread Length (mm) | WAF (mm) | Head Height (mm) |
|---|---|---|---|---|
| M6 | 18 | 18 | 10 | 4 |
| M8 | 22 | 22 | 13 | 5.3 |
| M10 | 26 | 26 | 17 | 6.4 |
| M12 | 30 | 30 | 19 | 7.5 |
| M16 | 38 | 38 | 24 | 10 |
| M20 | 46 | 46 | 30 | 12.5 |
Practical Considerations for Engineers
Interchangeability
For most applications, ISO 4017 bolts can replace DIN 933 bolts without issue, as the thread length and head dimensions are identical for common sizes. However, for sizes above M24, DIN 933 may have different thread lengths; always consult the standard.
Standards Migration
Many industries are transitioning from DIN to ISO standards. If your design specifies DIN 933, you can typically substitute ISO 4017, but verify with your quality department. For new designs, specify ISO 4017 to ensure global compatibility.
Testing and Certification
Both standards require mechanical testing per ISO 898-1. Key tests include:
- Proof load test: Verifies the bolt can withstand a specified load without permanent deformation.
- Tensile test: Measures ultimate tensile strength and yield strength.
- Hardness test: Typically Rockwell or Vickers, to ensure proper heat treatment.
Conclusion
ISO 4017 and DIN 933 are functionally equivalent for most fastener applications, with minor dimensional differences that rarely affect performance. Engineers should specify ISO 4017 for new designs to align with international standards. Precision Fasteners Manufacturer supplies ISO 4017 and DIN 933 hex bolts in carbon steel, alloy steel, and stainless steel grades with factory-direct pricing. Contact us for a quote.
