Extra Fine Thread Hexagon Head Bolts

When precision assembly and reliable clamping force matter, our inventory is built around fasteners that deliver consistent performance under load. Products like Fine Thread Hex Head Bolts and Fine Pitch Hex Cap Bolts are stocked in various diameters to suit general machining and structural frameworks. These items share a focus on tighter thread geometry, which increases thread engagement length and distributes stress more evenly across the joint. The hexagon head design, paired with fine pitch threading, allows for higher torque transmission without stripping, making them a preferred choice for assemblies that experience thermal cycling or dynamic loads. Engineers appreciate the reduced tendency to loosen under vibration, and our range covers multiple material grades and protective coatings to match specific environmental conditions.

The Extra Fine Thread Hexagon Head Bolts take thread density a step further for applications where space constraints or sealing requirements demand maximum thread contact within a limited grip length. Each bolt is cold-formed and rolled to maintain grain flow integrity, then precision-trimmed to meet ASME B1.1 profiles. This manufacturing process yields exceptional fatigue resistance, which is critical in high-cycle machinery, hydraulic manifolds, and precision tooling. A full-bodied hex head with washer-facing provides a generous load-bearing surface, reducing embedment into softer mating components. These bolts are regularly specified in aerospace ground support, scientific instrument assembly, and fluid power equipment, where the extra fine pitch effectively resists pressure-induced bolt stretch and creates a more reliable seal when used with O-ring or gasket joints. They are offered in unified extra fine (UNEF) and metric fine thread variants to serve global supply chains.

Core Features & Dimensional Tolerances

• Threads per inch follow UNEF standards, with typical TPI values of 32 for 1/4” and 5/16” diameters, and 20–28 for sizes above 3/8”.
• Metric extra fine versions (e.g., M8×0.75, M10×1.0) are kept in warehouse for immediate dispatch.
• Hex width across flats conforms to ASME B18.2.1 for inch-based sizes and ISO 4014 for metric equivalents.
• Thread class is 2A/3A as standard, with tighter 3A class available to order for critical stud applications.
• Length tolerance holds ±0.005” on short screws and ±0.010” beyond 6”, verified via optical sorting systems.
• Surface roughness on bearing face is kept below 63 Ra microinches to minimize friction scatter during torque sequencing.
• Plating options include zinc clear, zinc yellow, black oxide, hot-dip galvanized, and cadmium replacement coatings such as zinc-nickel.

Mechanical & Material Specifications