How to Install BoxBolts: Step-by-Step Guide
BoxBolts are structural blind fasteners for connecting to hollow structural sections and other steel members where access is only on one side. They remove the need for welding or through bolting, speed up install work, and meet common approvals. If you want a clean, safe blind connection, install BoxBolts.
Quick Answer, how do you install BoxBolts?
Drill the correct hole size, insert the BoxBolt until the shoulder is flush, hold the hex shoulder with a wrench, then tighten the core bolt to the specified torque. The internal cone expands the sleeve inside the hollow section for a secure blind connection. Use the BoxSok tool to speed up one tool installation.
Step-by-Step Installation Guide
Step 1, prepare the hole
Mark and drill a standard diameter hole through the steel per your design and AISC 360 practices. Keep the hole within tolerance, remove burrs, and clean the surface for proper seating.
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- Focus keyphrase note, install BoxBolts into correctly sized holes only.
- Rule of thumb, the hole should be close to the BoxBolt body diameter, do not oversize.
Step 2, align the connection
Position the bracket, plate, or member so the holes align cleanly. Confirm fit up before inserting hardware.
Step 3, insert the BoxBolt
Slide the BoxBolt through the connected parts until the underside of the hex shoulder sits flush on the outer surface.
Step 4, hold the shoulder
Place an open ended wrench on the hex shoulder to prevent rotation during tightening.
Step 5, tighten the core bolt
Use a ratchet or impact wrench, or use the BoxSok tool for faster one tool installation. As you tighten, the cone draws into the sleeve, expanding inside the hollow section.
Step 6, torque check
Tighten to the specified torque for the size used. Verify with a torque wrench as required by the specification or QA plan.
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- Example targets often used, 18 ft lb for 5/16 inch, 59 ft lb for 1/2 inch, 140 ft lb for 5/8 inch. Always follow current manufacturer data.
Tips, safety notes, and common mistakes
- Hole tolerance matters. Oversized holes can reduce clamping performance. Keep holes within the specified limit.
- Edge distance and spacing. Maintain minimum edge distances and spacing per your design and the product data to avoid cracking or tear out.
- Use BoxSok for speed. One tool tightening cuts install time and helps with repeatable torque.
- Surface prep helps. Remove paint, burrs, or debris that could prevent the shoulder from seating flush.
- Do not weld after install. Heat can compromise the fastener. If welding is needed near the area, protect or remove hardware first.
- Document torque checks. Add a simple QA checklist for inspectors and sign off at each connection point.
Related Resources
FAQs about installing BoxBolts
What tools do I need to install BoxBolts?
A standard wrench or ratchet works fine, and the BoxSok tool enables one tool installation, which speeds things up and helps with repeatable torque.
Can BoxBolts be used in seismic applications?
Yes, specific BoxBolt types are approved for seismic categories A through F. Always check the current technical data to confirm suitability for your project.
What finishes are available?
Zinc plated, hot dip galvanized, and stainless steel options are available to match the corrosion conditions of your site.
How are BoxBolts different from regular bolts?
BoxBolts expand internally inside hollow sections to form a blind connection, which is useful where through bolting is not possible and welding is undesirable.
Conclusion
Install BoxBolts with a simple process, prepare, align, insert, tighten, and torque check. You get a fast, clean, code friendly blind connection that avoids hot work. For sizes, torque values, and approvals, see the official BoxBolt page.
Last reviewed: August 25, 2025
