How to Fit Heavy Duty Bolts

Blindbolt NZ | 18th March 2021

Heavy Duty Bolt

Heavy Duty Bolt

Heavy duty bolts provide the ideal solution when heavy weight steel sections need to be fastened. This guide offers step by step instructions for the safe, quick and seamless installation of heavy duty bolts.

A Brief Introduction to Heavy Duty Bolts

Heavy duty bolts are also known as HD bolts. They offer an alternative to traditional blind bolts when the join being created features a shear plane which would otherwise cross the legs of the blind bolt. Heavy duty bolts are shorter than blind bolts and are the ideal solution for construction companies and manufacturers in circumstances which mean that other types of blind bolt wouldn’t be suitable.

How To Fit A Heavy Duty Bolt

One of the biggest advantages of using heavy duty blind bolts on construction projects is the fact that they are quick and simple to install. A heavy duty bolt can be fitted by following these steps:

Step 1: Make use of the table below when drilling a fixing hole in the components being connected. Ensure that you’re certain of the diameter, clamping range and depth clearance required for the project in question.

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: Once the fixing hole is drilled insert the heavy duty bolt. When a heavy duty bolt is being placed into a pre-drilled fixing hole, you should always be certain that the depth is enough to activate the bolt legs.

Step 3: Take a hammer and strike the activation pin located at the head of the bolt. Doing this will force the anchor legs apart at the base of the bolt, shifting them into the locked position. The activation pin needs to be flush to the bolt head in order to ensure that the bolt legs have been fully activated.

Step 4: You now need two spanners – one should be used to brace the HD bolt to the machined flats at the head of the bolt, while the other is used to tighten the nut. The table below will enable you to calculate the pre-loaded torque required:

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 our heavy duty bolt by clicking here

What Are the Advantages of Heavy Duty Bolts?

The activation pin mechanism of heavy duty bolts, combined with the expanding, locking legs is a unique combination, offering quick and cost effective installation across the construction industry. The installation process needs just a hammer, two spanners and a supplied nut, and can be completed in a few simple steps. This offers the kind of speed and efficiency which is hugely valued in industries such as construction and manufacturing.

What to Take Away

Heavy duty bolts, which are sometimes called HD bolts, provide an alternative to conventional blind bolts when heavy steel sections are being joined, or when a project requires shorter fixings. The unique nature of the activation and locking systems of HD bolts means that installation is quick and simple, using just a few simple instructions. Once the fixing hole has been drilled the bolt is put in place and then a hammer strikes the activation pin, which activates the legs, locking them into position. When this has been done, a spanner is used 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 0800 42 52 62 or by emailing us at

Heavy Duty Bolts

Heavy Duty Bolts

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