How to Fit Heavy Duty Bolts

Blind Bolt US | 18th March 2021

Heavy Duty Bolt

Heavy Duty Bolt

What are heavy duty bolts? They are the ideal solution for fastening heavier steel sections, and in this guide we offer step by step instructions for heavy duty bolt installation which is quick, seamless and safe.

A Brief Introduction to Heavy Duty Bolts

Heavy duty bolts also go by the name ‘HD bolts’. They offer an alternative to the traditional blind bolt whenever the shear plane in question would cross the legs of any blind bolt installed. The fact that heavy duty bolts are shorter fixings makes them the ideal choice when other types of blind fastener aren’t suitable.

How To Fit A Heavy Duty Bolt

The quick and simple nature of the installation process for heavy duty bolts is one of the major benefits they offer. The following is a step by step guide to fitting a heavy duty bolt:

Step 1: Consult the table below when drilling a fixing hole in the components being connected. It will enable you to calculate the clamping range, diameter and depth clearance of the project being worked on.

Product Code Bolt Size Hole Diameter Clamping Range (Min) Clamping Range (Max) Depth Clearance
HD0845ZF M8 x 45 8 7 25 10
HD1045ZF M10 x 45 10 7 25 12
HD1060ZF M10 x 60 10 7 40 12
HD1245ZF M12 x 45 12 8 22 15
HD1260ZF M12 x 60 12 8 37 15
HD1660ZF M16 x 60 16 12 30 25
HD1675ZF M16 x 75 16 12 45 25
HD2070ZF M20 x 70 20 15 32 30
HD2085ZF M20 x 85 20 15 47 30

(All values in mm unless stated otherwise)

Step 2: The heavy duty bolt is then inserted into the pre-drilled hole, ensuring that there is sufficient depth for the bolt legs to be activated.

Step 3: Using a hammer, strike the activation pin located at the head of the bolt. Doing this will force apart the anchor legs at the base, shifting them into a locked position. Try to hit the pin head-on. The bolt legs will be fully activated only when the activation pin is flush to the bolt head.

Step 4: Take the first spanner and brace the heavy duty bolt to the machined flats at the head of the bolt, then use the second spanner to tighten the nut. The table below will give the optimum pre-loaded torque needed:

Bolt Size Recommended Pre-load Geomet 500B Tightening Torque(Nm) A4-70 Stainless Steel
M8 20 18
M10 35 24
M12 45 30
M16 95 45
M20 120 80


You can view a short video demonstrating how to fit a heavy duty bolt here.

What Are the Advantages of Heavy Duty Bolts?

The activation pin and expanding, locking legs of heavy duty bolts are unique, and provide quick, cost effective installation across a range of construction projects. Full installation can be completed using just a hammer, spanners and a supplied nut, in a few simple steps. When industries like construction and manufacturing value efficiency and adopt the maxim that ‘time is money’ heavy duty bolts are the obvious choice.

What to Take Away

Heavy duty bolts, or HD bolts, are the ideal alternative to conventional blind bolts when heavy steel sections need to be joined or a project calls for shorter fixings. The unique nature of the activation and locking system means that installing heavy duty bolts is quick and simple if a few easy instructions are followed. Drill the fixing hole, place the bolt, strike the activation pin to activate and lock the legs and then use a spanner to tighten the nut.

Interested in finding out more about our heavy duty bolts (HD bolts) and how they can benefit your projects and tasks? Get in touch and speak to a member of the BlindBolt team by using the contact form below. You can also contact a member of our team on (630)882-9010 or by emailing us at

Heavy Duty Bolts

Heavy Duty Bolts

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