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April 15, 2026Hex cap nuts (or dome nuts or acorn nuts) are commonly used fastening elements that are used to offer functionality and appeal. These nuts are characterized by a closed-end dome structure, which covers the exposed threads of a bolt, which protects against corrosion and dirt, and mechanical damage and enhances safety by removing sharp edges.
Hex cap nuts are also commonly utilized in the automotive, furniture, construction and decorative industry where clean finish and added protection is needed. Their weight, dimensions, and specifications are important aspects that engineers, fabricators, and procurement professionals in the manufacturing and assembly processes should understand.
This guide includes hex cap nut weight charts, standard sizes, thread, material differences, and uses to allow you to select the correct fastener to meet your requirements.

What Are Hex Cap Nuts?
Hex cap nuts are domed nuts that are six sided and cover the end of the bolt. They do not permit the bolt to pass through the entire nut as in the standard hex nuts, so they will be ideal in applications where a finished appearance and protection are needed.
Key Features:
- Dome-shaped closed end
- Flat hex base to easily tighten.
- Coats threads to prevent corrosion and damage.
- Enhances safety by enveloping sharp ends of bolts.
- In imperial and metric sizes.

Hex Cap Nuts Dimensions (DIN 980 Standard Reference)
Hex Cap Nuts (all-metal prevailing torque lock via deformed threads) – Metric coarse thread standard.
| Thread Size | Pitch | s (Width across flats) | m (Height) | e (Across corners) | d2 (Inside Ø) | Weight (kg/1000 pcs) |
| M4 | 0.7 | 7.0 | 3.5 | 7.66 | 4.2 | 1.13 |
| M5 | 0.8 | 8.0 | 4.0 | 8.79 | 5.1 | 1.73 |
| M6 | 1.0 | 10.0 | 5.0 | 10.89 | 6.2 | 2.50 |
| M8 | 1.25 | 13.0 | 6.5 | 14.20 | 8.0 | 5.27 |
| M10 | 1.5 | 17.0 | 8.0 | 18.52 | 10.3 | 9.58 |
| M12 | 1.75 | 19.0 | 10.0 | 20.88 | 12.7 | 13.70 |
| M16 | 2.0 | 24.0 | 13.0 | 26.17 | 16.7 | 28.50 |
| M20 | 2.5 | 30.0 | 16.0 | 32.95 | 20.2 | 52.30 |
| M24 | 3.0 | 36.0 | 19.0 | 39.55 | 24.6 | 92.10 |
| M30 | 3.5 | 46.0 | 24.0 | 50.85 | 30.5 | 175.00 |
Tolerances: Class 6 (medium), Thread 6G
Locking Feature: Deformed top threads create prevailing torque
Standards: DIN 980 (Type V), ISO 4035 equivalent

Thread Pitch Chart (Metric Standard – ISO 261 / DIN 13)
Standard coarse and fine pitches for common fastener sizes. Bold = Coarse (most common).
| Thread Size | Coarse Pitch | Fine Pitch 1 | Fine Pitch 2 | Fine Pitch 3 |
| M1.6 | 0.35 | 0.2 | – | – |
| M2 | 0.4 | 0.25 | – | – |
| M3 | 0.5 | – | – | – |
| M4 | 0.7 | – | – | – |
| M5 | 0.8 | – | – | – |
| M6 | 1.0 | – | – | – |
| M8 | 1.25 | 1.0 | 0.75 | – |
| M10 | 1.5 | 1.25 | 1.0 | 0.75 |
| M12 | 1.75 | 1.5 | 1.25 | 1.0 |
| M14 | 2.0 | 1.5 | 1.25 | 1.0 |
| M16 | 2.0 | 1.5 | 1.25 | 1.0 |
| M20 | 2.5 | 2.0 | 1.5 | – |
| M24 | 3.0 | 2.0 | 1.5 | – |
| M30 | 3.5 | 2.0 | – | – |
| M36 | 4.0 | 3.0 | – | – |
Thread Tolerances: 6g (external), 6H (internal)
Standards: ISO 261, ISO 262, DIN 13
Usage: Coarse for general, Fine for vibration/high preload
Hex Cap Nuts – Materials Available
| Material Category | Common Grades/Specs | Applications | Key Properties |
| Carbon Steel | Grade 5, 8.8, 10.9 | General industrial, Machinery | Cost-effective, high strength |
| Alloy Steel | A194 Gr.2H, 8 | High temp/pressure | Heat resistant up to 400°C |
| Stainless Steel | SS 304 (A2-70), SS 316 (A4-80) | Marine, Food, Chemical | Corrosion resistance, hygienic |
| High Tensile | Grade 8.8, 10.9 | Automotive, Heavy equipment | Vibration resistant, 800+ MPa |
| Brass | IS 319 | Electrical fittings | Machinability, conductivity |
| Monel | Monel 400 (N04400) | Marine, Acidic | Seawater corrosion resistance |
| Inconel | Inconel 625 | High temperature | Oxidation >800°C |
How to Calculate Hex Cap Nut Weight
If a standard chart is not available, weight can be calculated using:
Formula:
Weight = Volume × Density
Where density of steel ≈ 7850 kg/m³
Hex cap nuts can be approximated as a hex body with a hemispherical dome minus the threaded hole.
Example (M8):
- Approximate volume: 1.34 × 10⁻⁶ m³
- Weight ≈ 1.34 × 10⁻⁶ × 7850 ≈ 0.0105 kg
This aligns with standard chart values.
Hex Cap Nuts – Material Impact on Weight
Weight comparison using M10 size (baseline: Carbon Steel 9.58 kg/1000 pcs). Stainless adds ~2-8% due to higher density.
| Material | Density (g/cm³) | Weight M10 (kg/1000) | % Increase vs CS | Cost Factor | Corrosion Rating |
| Carbon Steel | 7.85 | 9.58 (Baseline) | 0% | 1x | Low (needs coating) |
| Zinc Plated CS | 7.87 | 9.65 | +0.7% | 1.1x | Medium (indoor/outdoor) |
| HDG Carbon Steel | 7.90 | 9.72 | +1.5% | 1.3x | High (coastal) |
| SS 304 (A2-70) | 8.00 | 9.80 | +2.3% | 3x | High (chemicals) |
| SS 316 (A4-80) | 8.02 | 9.82 | +2.5% | 4x | Excellent (marine) |
| High Tensile 8.8 | 7.85 | 9.58 | 0% | 1.5x | Low (coated) |
Key Insight: Stainless steel nuts are only 2-3% heavier than carbon steel but 3-4x more expensive. Use CS + coating for cost savings unless corrosion is critical.
Common Sizes & Applications – Hex Cap Nuts
| Size | Primary Applications | Industry | Load Rating | Key Advantages |
| M4-M6 | Safety covers, Trim | Automotive, Appliances | Light duty | Aesthetic finish, tamper protection |
| M8-M10 | Machinery guards | Manufacturing | Medium duty | Vibration resistance, thread protection |
| M12 | Equipment panels | Industrial | Heavy duty | Exposed bolt protection, clean look |
| M16-M20 | Heavy machinery | Construction, Agriculture | Very heavy | Safety, prevents snagging |
| M24+ | Structural covers | Oil & Gas, Power | Extreme duty | High pressure seals, safety critical |
Most Popular Sizes: M8 (30%), M10 (25%), M12 (20%)
Benefits: Protects threads from damage, prevents injury, improves aesthetics
Conclusion
The Hex cap nuts can be used in various industries as they can be used as a functional, safety and aesthetic fastening solution. Their closed-end design does not only offer protection to threads, but also improves the overall looks of assemblies.
Knowledge of the hex cap nuts weight chart, dimensions, materials and thread specifications, enables proper planning of materials, estimation of cost and efficient production. In the light-duty or heavy industrial configurations, the appropriate size and material will guarantee durability and longevity of performance.
With standardized data and the best practices, engineers and procurement team can streamline their efficiency and reliability in fastening solutions.
