Introduction to DIN 933 Hex Bolts
DIN 933 specifies fully threaded hexagon head bolts with metric coarse threads, designed for high-strength fastening in mechanical assemblies. These bolts feature a hexagonal head for easy wrenching and are widely used where full threading is required for secure engagement. The standard ensures compatibility and reliability across industries, adhering to precise tolerances for dimensions such as head height, width across flats, and thread pitch.
Compared to partially threaded variants like DIN 931, DIN 933 bolts provide uniform thread distribution, ideal for applications with variable nut positions. They are available in coarse and fine thread options, with coarse being the default due to its superior root strength and commonality in general engineering. Materials typically include stainless steels like AISI 304 and 316 for corrosion resistance, ensuring longevity in harsh environments.
This guide, based on established industry standards, details specifications, materials, and uses to aid in selection and application, promoting optimal performance and safety in designs.
Comparison with Related Standards
DIN 933 bolts partially align with GB 5783, the Chinese standard for hex head bolts. While core specifications like thread pitch and nominal diameters match, subtle differences exist in head dimensions for sizes such as M8, M10, M12, and M20. For instance, GB 5783 heads are slightly smaller, measurable via calipers but not visually apparent. This allows interchangeability in most cases, though precision applications demand standard-specific selection to avoid fit issues.
Equivalently, DIN 933 corresponds to ISO 4017, emphasizing full threading and metric dimensions. Engineers should verify compliance when substituting, as tolerances for grades A and B may vary slightly, impacting assembly precision.
Types and Grades
Hex bolts under DIN 933 are categorized by thread type and product grade:
- Thread Types: Coarse thread offers high root strength for load-bearing; fine thread provides higher precision for vibration-prone settings. Coarse is standard and most prevalent.
- Product Grades: A, B, and C. Grade C is economical with rougher finish for low-demand uses; Grades A and B offer tighter tolerances and smoother surfaces for high-precision assemblies, albeit at higher cost.
Additionally, bolts come in full-thread (DIN 933) or half-thread configurations, with full-thread suited for through-hole fastening.
Dimensional Specifications
The following table outlines key dimensions for DIN 933 hex bolts from M4 to M22, corrected and verified against standard references. All values are in millimeters. Note that Grade A provides tighter tolerances for critical applications, while Grade B is suitable for general use. Length ranges are indicative; custom lengths are possible.
| Screw Thread d | Pitch P | Head Height k Nominal | k Grade A max/min | k Grade B max/min | Across Flats s Nominal | s Grade A min | s Grade B min | Across Corners e Grade A min | Across Corners e Grade B min | Length Range (mm) |
|---|---|---|---|---|---|---|---|---|---|---|
| M4 | 0.7 | 2.8 | 2.92/2.68 | 3/2.6 | 7 | 6.78 | 6.64 | 7.66 | 7.5 | 8-40 |
| M5 | 0.8 | 3.5 | 3.65/3.35 | 3.74/3.26 | 8 | 7.78 | 7.64 | 8.79 | 8.63 | 8-65 |
| M6 | 1 | 4 | 4.15/3.85 | 4.24/3.76 | 10 | 9.78 | 9.64 | 11.05 | 10.89 | 10-150 |
| M7 | 1 | 4.8 | 4.95/4.65 | 5.04/4.56 | 11 | 10.73 | 10.57 | 12.12 | 11.94 | 10-150 |
| M8 | 1.25 | 5.3 | 5.45/5.15 | 5.54/5.06 | 13 | 12.73 | 12.57 | 14.38 | 14.2 | 12-200 |
| M10 | 1.5 | 6.4 | 6.63/6.22 | 6.69/6.11 | 17 | 16.73 | 16.57 | 18.9 | 18.72 | 16-200 |
| M12 | 1.75 | 7.5 | 7.68/7.32 | 7.79/7.21 | 19 | 18.67 | 18.48 | 21.1 | 20.88 | 20-200 |
| M14 | 2 | 8.8 | 8.98/8.62 | 9.09/8.51 | 22 | 21.67 | 21.16 | 24.49 | 23.91 | 25-200 |
| M16 | 2 | 10 | 10.18/9.82 | 10.29/9.71 | 24 | 23.67 | 23.16 | 26.75 | 26.17 | 25-200 |
| M18 | 2.5 | 11.5 | 11.72/11.28 | 11.85/11.15 | 27 | 26.67 | 26.15 | 30.14 | 29.56 | 30-150 |
| M20 | 2.5 | 12.5 | 12.72/12.28 | 12.85/12.15 | 30 | 29.67 | 29.16 | 33.53 | 32.95 | 30-150 |
| M22 | 2.5 | 14 | 14.22/13.78 | 14.35/13.65 | 32 | 31.61 | 31 | 35.72 | 35.03 | 30-150 |
These dimensions ensure interoperability; for fine threads, specify requirements as they alter pitch and strength characteristics. Always measure with calibrated tools for verification.
Materials and Chemical Compositions
DIN 933 bolts are primarily produced in stainless steel for durability. Common grades include SUS304 (A2) and SUS316 (A4), with SUS316 offering enhanced corrosion resistance via molybdenum addition.
| Materiaal | C (%) | Mn (%) | Si (%) | P (%) | S (%) | Ni (%) | Mo (%) | Cr (%) |
|---|---|---|---|---|---|---|---|---|
| SUS304 roestvrij staal | ≤0,08 | ≤2,00 | ≤1,00 | ≤0,045 | ≤0,03 | 8.00-11.00 | – | 17.00-19.00 |
| SUS316 roestvrij staal | ≤0,08 | ≤2,00 | ≤1,00 | ≤0,045 | ≤0,03 | 10.00-14.00 | 2.00-3.00 | 16.00-18.00 |
SUS304 suits general environments; SUS316 is ideal for marine or chemical exposure. Material choice affects tensile strength and environmental resilience.
Performance and Torque Standards
Performance grades for stainless steel DIN 933 bolts typically range from A2-50 to A4-80, denoting yield and tensile strengths. For A2-70 (common for SUS304), tensile strength is 700 MPa, yield 450 MPa. Torque values depend on size and lubrication; for dry assembly, M8 requires approximately 23 Nm for 8.8 grade equivalent, but adjust for stainless (lower friction).
Standard torque guidelines ensure preload without thread stripping. For precise applications, use torque wrenches calibrated to ISO standards, considering factors like thread condition and material pairing.
Advantages and Applications
DIN 933 hex bolts excel in versatility, offering:
- High torque transmission via hex head.
- Full threading for adjustable fastening.
- Corrosion resistance in stainless variants.
Applications span construction (structural joints), railways (track fastening), and machinery (assembly lines), where reliability under load is paramount.
Installation Guidelines
Proper installation involves aligning threads, applying even torque, and using washers for load distribution. For high-vibration areas, employ locking nuts. Follow torque specs to avoid over-tightening, which can lead to failure.
Veelgestelde vragen (FAQ)
What are the key differences between DIN 933 and GB 5783?
While interchangeable in many cases, GB 5783 has slightly smaller head sizes for M8, M10, M12, and M20. Use calipers to verify dimensions for precision fits.
When should I choose fine thread over coarse?
Fine threads offer better precision and vibration resistance, ideal for machinery; coarse threads provide stronger roots for heavy loads in construction.
What material is best for corrosive environments?
SUS316 stainless steel, with molybdenum, resists pitting in marine or chemical settings better than SUS304.
How do product grades A, B, and C differ?
Grade C is cost-effective with rougher finish for general use; A and B have tighter tolerances for high-precision assemblies.
What torque should be applied to an M10 DIN 933 bolt?
For A2-70 grade, dry torque is around 37 Nm; always reference material-specific charts and use calibrated tools.
Can DIN 933 bolts be used in high-temperature applications?
Stainless variants handle up to 800°C, but verify with standards like ISO for extreme conditions to ensure integrity.
