Structural Blind Bolts are selected when an assembly calls for structural and machine joints that must be tightened to a controlled preload. This application guide to the Trade series (structural blind bolts) type covers concrete end-uses, the specification checklist, correct installation, and where an alternative fastener performs better.
Typical Applications for Structural Blind Bolts
The most common settings where these are specified:
- Structural steel: bolting beams, base plates and bracing where a defined preload and property class are required.
- Automotive & transport: chassis, suspension and powertrain mounting points subject to vibration.
- Heavy machinery: securing gearboxes, frames and guarding on plant that sees shock loads.
- Energy & infrastructure: tower, pylon and pipework supports exposed to weather and long service life.
- General machine building: fastening covers, brackets, motors and sub-assemblies on production equipment.
How to Specify Structural Blind Bolts for Your Application
- Size: Match the size to the mating part — see the dimension table below for each option.
- Strength class: Choose the property class (e.g. 8.8, 10.9, 12.9 or A2/A4 stainless) for the load and environment, and tighten to the matching torque so the joint relies on preload, not friction.
- Environment: For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient.
- Standard: This product is supplied to Trade series (structural blind bolts). Quoting the standard on your order guarantees interchangeable dimensions between suppliers.
Installation & Assembly Practice
- Tighten to the torque for the size and property class with a calibrated wrench — the joint is held by preload, not by the thread friction alone.
- Ensure at least one full thread projects beyond the nut after tightening, and never re-use a bolt that has been tightened into yield.
- Under slotted or oversized holes, fit a hardened washer so the preload does not relax into the hole edge.
Common Selection Mistakes with Structural Blind Bolts
- Specifying class 12.9 "to be safe" in a corrosive environment — high classes are more sensitive to hydrogen embrittlement and stress corrosion; 8.8 hot-dip galvanized often outlasts them outdoors.
- Choosing a length that puts the shear plane through the threaded portion when a plain shank (partially threaded bolt) was available.
- Mixing stainless bolts with plated-steel nuts: the joint loses its corrosion logic and can gall or seize.
Where Structural Blind Bolts Are Not the Right Choice
Not for permanent joints that will never be opened (a rivet or weld is cheaper), and not where the head must sit flush — use a countersunk screw instead.
