The Hexagon Head Bolt (often called hex bolt) is a standard, high-strength fastener with a six-sided (hexagonal) head and external machine threads. It is designed to mate with nuts or pre-tapped holes, delivering reliable clamping force for assembling two or more components, and is widely recognized for easy installation/removal via wrenches or socket tools.
• Core Design Features: The hexagonal head provides maximum torque transmission, ensuring secure tightening; external machine threads (available in coarse [UNC] or fine [UNF] pitches) enable precise mating with nuts/threads; most variants have a plain shank (smooth section between head and threads) to reduce friction during installation.
• Common Materials:
◦ Carbon steel (e.g., 8.8/10.9 grade): For industrial machinery and structural applications requiring high tensile strength.
◦ Stainless steel (e.g., 304/316): For corrosion resistance in humid, outdoor, or food-grade environments.
◦ Alloy steel (e.g., alloy with chromium/molybdenum): For heavy-duty scenarios like automotive engines or construction equipment.
• Surface Treatments: Typically finished with zinc plating (rust protection), hot-dip galvanizing (enhanced corrosion resistance for outdoor use), black oxide (wear resistance + matte appearance), or passivation (boosts stainless steel’s anti-rust performance).
• Key Applications: Essential in machinery manufacturing, automotive assembly, construction (e.g., steel structures), electrical equipment, and household appliances—any scenario needing durable, detachable component fastening.
| THREAD SIZE D | M16 | M20 | (M22) | M24 | (M27) | M30 | M36 | |
| P Pitch of thread | 2 | 2.5 | 2.5 | 3 | 3 | 3.5 | 4 | |
| bref for length / Nom <100/>100 | 31 | 36 | 38 | 41 | 44 | 49 | 56 | |
| 38 | 43 | 45 | 48 | 51 | 56 | 63 | ||
| c | Max | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 |
| Min | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 | |
| dₐ | Max | 18.7 | 23.24 | 25.24 | 27.64 | 31.24 | 34.24 | 41 |
| dₛ | Max | 16.7 | 20.84 | 22.84 | 24.84 | 27.84 | 30.84 | 37 |
| Min | 15.3 | 19.16 | 21.16 | 23.16 | 26.16 | 29.16 | 35 | |
| dw | Max | † | † | † | † | † | † | † |
| Min | 24.9 | 31.4 | 33.3 | 38 | 42.8 | 46.5 | 55.9 | |
| e | Min | 29.56 | 37.29 | 39.55 | 45.2 | 50.85 | 55.37 | 66.44 |
| k | Nom | 10 | 12.5 | 14 | 15 | 17 | 18.7 | 22.5 |
| Max | 10.75 | 13.4 | 14.9 | 15.9 | 17.9 | 19.75 | 23.55 | |
| Min | 9.23 | 11.6 | 13.1 | 14.1 | 16.1 | 17.65 | 21.45 | |
| k’ | Min | 6.5 | 8.1 | 9.2 | 9.9 | 11.3 | 12.4 | 15 |
| r – Min | Min | 0.6 | 0.8 | 0.8 | 1 | 1.2 | 1.2 | 1.5 |
| s | Max | 27 | 34 | 36 | 41 | 46 | 50 | 60 |
| Min | 26.16 | 33 | 35 | 40 | 45 | 49 | 58.8 | |
| Chamfer length z | Max | 3 | 3.8 | 3.8 | 4.5 | 4.5 | 5.3 | 6 |
| Note-Sizes shown in brackets are at second preference, * For galvanized bolts, dimension apply before galvanizing. †dw’ Max = s actual. | ||||||||