How to Fit a Heavy Duty Bolt?

Blindbolt UK | 15th March 2021

Heavy Duty Bolt

Heavy Duty Bolt

Heavy duty bolts were developed to provide an effective solution for fastening heavyweight steel sections. In this guide, we'll provide step-by-step instructions to facilitate safe, quick and seamless heavy duty bolt installation.

A Brief Introduction to Heavy Duty Bolts

A heavy duty bolt, also known as an HD bolt, is a type of fastening, which provides an alternative to the traditional blind bolt in cases where a shear plane would ordinarily cross the legs of the blind bolt. Heavy duty bolts are shorter fixings, which can be used by manufacturers and construction companies where other types of blind fastener would not be suitable.

How To Fit A Heavy Duty Bolt

One of the most significant benefits of using heavy duty blind bolts in the construction industry is the ease and speed of installation. To fit a heavy duty bolt, follow these steps:

Step 1: Using the table provided below, drill a fixing hole in both of the components you plan to connect. Calculate the diameter, the clamping range and the depth clearance required for your individual project.

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


Step 2: Insert the heavy duty bolt into the fixing hole. When placing HD bolts into a pre-drilled fixing hole, always allow sufficient depth to activate the bolt legs.

Step 3: Select a suitable hammer and then strike the activation pin, which is located at the head of the bolt. Aim to hit the pin head-on. This action will force the anchor legs of the bolt apart at the base, moving them into a locked position. It is important to note that the activation pin should be flush to the bolt head to ensure full activation of the bolt legs.

Step 4: Using a spanner, brace the HD bolt to the machined flats located at the head of the bolt and tighten the nut using an additional spanner. Use the table supplied below to determine optimum pre-loaded torque

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 our short video demonstrating how to fit a heavy duty bolt by clicking here.

What Are the Advantages of Heavy Duty Bolts?

Heavy duty bolts have a unique activation pin mechanism and expanding, locking legs, which affords swift, cost-effective installation within the construction industry. The installation process, which can be completed in just a few steps, requires only a hammer, spanners and a supplied nut. In construction and manufacturing, efficiency is key and time is of the essence, making this type of fastening an excellent choice.

What to Take Away

Heavy duty bolts, also known as HD bolts, offer an alternative to conventional blind bolts when joining heavy steel sections and working on projects that require shorter fixings. Featuring unique, innovative activation and locking systems, heavy duty bolts can be installed quickly and easily by following simple step-by-step instructions. The fixing hole is drilled, the bolt is placed and then a hammer is used to strike the activation pin, activate the legs and lock them in position. Finally, a spanner is utilised to secure 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 +61 3 9757 4989 or by emailing us at

HD Bolt

HD Bolt

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