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Galvanized & Blackened Double-Headed Bolts 4.8/8.8 Grade - China Suppliers & Factory
| Thread size d | M6 | M8 | M10 | M12 | M14 | M16 | M18 | M20 | M22 | M24 | M27 | M30 | M33 | |
| designation① | D | D | D | D | D | D | D | D | D | D | D | D | D | |
| / | / | D-HDZ | D-HDZ | D-HDZ | D-HDZ | D-HDZ | D-HDZ | D-HDZ | D-HDZ | D-HDZ | D-HDZ | D-HDZ | ||
| ds | Max | 5.32 | 7.16 | 8.99 | 10.83 | 12.66 | 14.66 | 16.33 | 18.33 | 20.33 | 22 | 25 | 27.67 | 30.67 |
| Min | 5.14 | 6.97 | 8.78 | 10.59 | 12.41 | 14.41 | 16.07 | 18.07 | 20.07 | 21.69 | 24.69 | 27.34 | 30.34 | |
| S | Public | 50 | 63 | 75 | 100 | 115 | 125 | 140 | 150 | 165 | 175 | 200 | 200 | 225 |
| Max | 75 | 88 | 100 | 125 | 140 | 150 | 165 | 175 | 190 | 200 | 225 | 225 | 250 | |
| Min | 42 | 55 | 67 | 92 | 107 | 117 | 132 | 142 | 157 | 167 | 192 | 192 | 217 | |
| Connecting nut | M6 | M8 | M10 | M12 | M14 | M16 | M18 | M20 | M22 | M24 | M27 | M30 | M33 | |
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The Function of Double Headed Bolts
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1. Connecting Mechanical Components Double headed bolts have threads at both ends and a screw in the middle, commonly used to connect mechanical components such as mining machinery, bridges, automobiles, motorcycles, boiler steel structures, suspension towers, large-span steel structures, and large buildings.
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2. Installation Accessories When large equipment requires the installation of accessories, such as observation mirrors, mechanical seal seats, reduction frames, etc., double headed bolts can play a role. One end is screwed into the main body, and after installing the accessories, the other end is equipped with a nut. Due to the fact that these attachments may require frequent disassembly, using double headed bolts for replacement would be very convenient.
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3. Connecting Thick Plates & Inconvenient Areas In cases where the thickness of the connectors is large or the connection area is not convenient to use hexagonal bolts, such as concrete roof trusses, roof beam suspensions, monorail beam suspensions, etc., double headed bolts are also a suitable choice.
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4. Fixed Connecting Rod Double headed bolts are also commonly used for mechanical fixed connecting rods, with corresponding threads at both ends. The thickness of the middle screw varies depending on actual usage.
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Frequently Asked Questions (FAQ)
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What is a double headed bolt and how does it differ from a standard bolt?
A double headed bolt (also called a stud bolt) has threads on both ends with a plain or threaded shank in the middle. Unlike a standard bolt which has a head on one end, a double headed bolt is designed to be screwed into a tapped hole on one side and secured with a nut on the other, making it ideal for applications requiring frequent disassembly.
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What thread sizes are available for double headed bolts?
Double headed bolts are available in a wide range of metric thread sizes, including M6, M8, M10, M12, M14, M16, M18, M20, M22, M24, M27, M30, and M33, to accommodate various structural and mechanical applications.
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What is the difference between the "D" and "D-HDZ" designations?
The "D" designation refers to standard double headed bolts, while "D-HDZ" refers to hot-dip galvanized versions. The HDZ coating provides enhanced corrosion resistance, making them suitable for outdoor, marine, or high-humidity environments. Note that D-HDZ is available from M10 and above.
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In which industries are double headed bolts most commonly used?
Double headed bolts are widely used across multiple industries including construction (bridges, large-span steel structures, concrete roof trusses), heavy machinery (mining equipment, boiler steel structures), transportation (automobiles, motorcycles), and infrastructure (suspension towers, monorail beam suspensions).
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Why should double headed bolts be used instead of hexagonal bolts in certain situations?
In situations where the connecting material is very thick or where there is limited space to maneuver a standard hexagonal bolt, double headed bolts offer a practical alternative. They allow secure fastening without requiring access to both sides of the joint, and they support frequent removal and reinstallation without damaging the base material.
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How do I select the correct double headed bolt size for my application?
Selection should be based on the thread size (d), shank diameter (ds Max/Min), and required grip length (S). Refer to the specification table above to match the thread size with the corresponding connecting nut and dimensional tolerances. Always ensure the bolt material and surface treatment (standard or HDZ) are appropriate for the operating environment.