Torsional Shear Type High-Strength Bolts
Torsional shear high strength bolts are suitable for friction-type connections in steel structures such as industrial and civil buildings, bridges, masts, boiler steel structures and lifting machinery; they are suitable for joints where there is sufficient space, bulk installation is required and visual inspection is convenient. They must not be used for pressure-bearing connections or in locations where there is insufficient space for operating a spanner.
Product Description
Torsional shear type high strength bolts are friction-type high-strength bolts with a fixed performance grade of 10.9S; they are commonly used in steel structure engineering.
One connection set = 1 bolt + 1 nut + 1 washer (Large hexagonal high-strength bolts require 2 washers)
The bolt shank features a star-shaped head (twelve-point head), and between the star-shaped head and the shank there is a pre-set torsional shear neck (a weakened cross-section), which is its most distinctive structural feature.
Performance Features
Mechanical Properties
The performance grade is fixed at 10.9S, with a tensile strength of ≥1000 MPa and a yield strength of ≥900 MPa. The bolts undergo quenching and tempering heat treatment, resulting in high strength and good toughness.
Force is transmitted via preload and friction between the plates; they are suitable only for friction-type connections and not for bearing-type connections.
Low variability in preload and high precision in preload control; excellent fatigue and seismic resistance, suitable for joints subjected to dynamic and cyclic loads.
One connection set comprises: 1 bolt + 1 nut + 1 washer, to be used as a matched set; components from different batches must not be mixed, and the set must not be reused.
Construction and Control Features
The end of the bolt features a torque-shear neck (weak cross-section) and a star-shaped head; when the designed pre-tension is reached, the torque-shear neck shears off and the star-shaped head detaches, thereby indicating that the bolt has been fully tightened.
Installation is carried out using a specialised electric torque-shear wrench; this eliminates the risk of human error in torque readings.
Quality inspection is straightforward: a visual check is made to confirm whether the star-shaped head has detached, eliminating the need for extensive torque spot checks and facilitating final acceptance.
Installation and Application Characteristics
Quick to install; suitable for large-scale, high-altitude steel structure work.
Disadvantages: More expensive than large hexagonal high-strength bolts; requires space at the tail end, making them unsuitable for use in confined joints; single-use only; cannot be dismantled and reused.
Construction
Principle of Operation
A specialised dual-sleeve torque-shear electric wrench is used: the inner sleeve secures the star-shaped head, whilst the outer sleeve rotates the nut;
during the tightening process, the bolt is subjected to tensile force, generating pre-tension; when the pre-tension reaches the design value, the torque-shear neck shears off, the star-shaped head detaches, and the tightening process is complete.
Construction procedures
Initial tightening: Pre-tighten to 60%–80% of the design pre-tension to eliminate gaps between panels;
Final tightening: Use a specialised spanner to break off the hexagonal head;
Bolt must be inserted freely into the hole; it is strictly forbidden to force the bolt in by hammering or to enlarge the hole using an oxy-acetylene torch; holes may only be enlarged by reaming.
Our Strengths
Manufacturer of high-strength fasteners
As a manufacturer at source, we maintain full in-house control over raw materials, heat treatment and phosphating. Our products are supplied as complete sets, with each batch accompanied by a certificate of conformity, test reports and torque coefficient reports; customisation options are available for phosphating, hot-dip galvanising and Dacromet anti-corrosion treatments. We offer a one-stop solution for high-strength large hexagonal head torque-shear bolts. We maintain ample stock of standard specifications, whilst non-standard lengths can be arranged for production. By eliminating the mark-ups of intermediaries, we support sample testing and guarantee a stable supply for your projects!