ASTM F1852 / EN 14399-10 Tension Control (TC) Heavy Hex Head Torsional Shear Bolt

Product Introduction
High-strength structural bolt assemblies manufactured to ASTM F3125 (consolidating former ASTM F1852 and F2280) for inch sizes, and to EN 14399-10 for metric sizes. Designed for preloaded joints in steel structures, each assembly comprises a heavy hex head bolt with a splined twist-off pintail, a hex nut, and a hardened washer. During installation, the pintail shears at a predetermined torque, giving visual confirmation that the required preload has been attained. Available in grades A325TC (8.8S) and A490TC (10.9S) per ASTM, or property class 10.9 per EN, in thread sizes 1/2″ to 1-1/8″ (inch) and M12 to M36 (metric).

Material & Mechanical Properties

• ASTM grades: A325TC (equivalent 8.8S) — minimum tensile strength 120 ksi for diameters ≤ 1″, proof load 85 ksi. A490TC (equivalent 10.9S) — tensile strength 150–173 ksi, proof load 120 ksi.

• Metric grade to EN 14399-10: property class 10.9 bolt with property class 10 nut.

• Nuts: ASTM A563 Grade DH; washers: ASTM F436 Type 1. All mechanical values are certified by lot with heat-number traceability.

Spline & Installation
The bolt features a splined pintail with a precision shear groove. A specialized electric shear wrench grips the nut (outer socket) and the pintail (inner drive), counter-rotating until the pintail shears cleanly. The twist-off provides immediate visual proof that design preload is achieved, eliminates torque wrenches and turn-of-nut methods, reduces operator error, and requires single-side access. No torsional shear stress is introduced into the bolt shank, avoiding preload relaxation commonly seen with torque-only techniques.

Head Types & Surface Finish
Standard head is heavy hex, providing a large bearing surface for load distribution and compatibility with structural steel assemblies. Round (button) head variants are also produced. Surface finishes: plain (uncoated), black oxide, phosphate, mechanical zinc plating, and hot-dip galvanizing (HDG) for outdoor environments. For metric EN 14399-10 assemblies, heavy hex head bolts are alloy steel with thread pitches from 1.75 mm to 3.5 mm. All finishes are applied under hydrogen embrittlement control for high-strength fasteners.

Assembly & Certification
Each bolt assembly is supplied as a matched set (bolt, nut, washer) from a single manufacturer to maintain CE marking under System 2+ and to ensure proper preload performance. Every component is traceable to the production lot with markings as required by the applicable standard.

Application Suitability
Steel-frame buildings, bridges, industrial plants, power generation facilities, transmission towers, offshore structures, and any steel erection project where structural integrity, rapid visual inspection, and high installation speed are required.

Technical Parameters