QUICK GUIDE TO SELECTING THE RIGHT NAIL FOR CONCRETE

Direct fastening on concrete

Not all nails are created equal

There’s a large variety of nails to choose from for direct fastening applications. It’s not always easy to understand the differences between the various nail types and to select the right nail for your needs.
Our fastening systems are designed to achieve maximum performance in a wide range of applications.

What determines nail performance

Multiple factors such as concrete properties, nail design and the fastening system used can influence how a nail performs on your jobsite.

The three main factors that define the suitability of a nail for use on concrete are: stick rate (i.e. the percentage of nails that hold securely), holding values and the cost of the nail.

How should you select the right nail for concrete?

Read on and find out more about the influencing factors.

1. Concrete basics

A nail penetrating concrete needs to create a hole for the shank by crushing and compacting the concrete. It also needs to withstand hitting hard aggregates as it finds its way into the concrete matrix. The resulting holding value achieved by the nail is directly linked to its embedment depth.

We distinguish between three concrete types:

Soft (S)

Low compressive strength (e.g. 2-5 ksi)
Small to medium-size aggregates; e.g. soft limestone
Example: lightweight concrete

Tough (T)

Medium to high compressive strength (e.g. 5-7 ksi)
Medium-size aggregate; e.g. pit gravel
Example: normal-weight concrete

Very tough (V)

High compressive strength (e.g. ≤ 7 ksi)
High proportion of large aggregates, mainly hard; e.g. quartz, granite
Example: high-performance concrete, very old concrete

2. Nail features

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Tip shape

The shape of the tip influences how well a nail is able to penetrate the concrete. Four different shapes are in use. The cut tip, the ballistic tip, the stepped shank and the long conical tip.

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Nail geometry

Length and diameter also affect how easily the nail penetrates the concrete.

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Nail hardness

A nail’s hardness influences how likely it is to be driven successfully. A harder nail is easier to drive into hard material. However, if the nail is too hard, it will break instead of bending when it hits a hard aggregate in the concrete. Therefore, a good nail is hard with enough ductility to bend, not break when hitting an aggregate.

3. Factors influencing your nail choice

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Stick rate

The stick rate indicates the percentage of nails being properly driven to the correct depth, i.e. with the permissible nail stand-off.

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Holding value

Holding values provide a measure of a nail's load-bearing capability. Loads can be split into two types: shear and tension. Shear loads act at right angles to the shank of the nail and tensile loads are concentric.

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The cost of the nail

The wide range of Hilti nails offers the most cost-efficient solution for various applications by allowing you to choose exactly the right nail for your requirements.

4. Nail classes

Different nails have been developed for various applications. They can be grouped in the five classes illustrated in the table below.

In general, assuming the nail is suitable for your application, light duty class V nails present the most economical solution as they are the least costly. Cost is directly related to the manufacturing technologies involved as well as the material from which the nails are made. Each higher nail class performs better under harsher conditions than the one below, but the manufacturing costs, and thus the price of the nail, increase with each nail class.

5. Embedment

An additional factor that influences nail performance is depth of embedment.
A nail that can be driven deeper generally has the ability to hold higher loads. However, if a nail needs to be driven deeper, there are two side effects: The stick rate decreases and higher driving energy is required because the nail has to penetrate further into the concrete.

6. Nails and concrete

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Stick rate of nail classes in different concrete types

Nail performance varies depending on the type of concrete and the distribution of its aggregates. Nails of all classes perform similarly in soft concrete, but as the concrete gets tougher, the stick rate varies.

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Stick rate versus holding values of nail classes

Differences between nails become clear in tough concrete. Premium nails perform better than less costly counterparts. See how depth of embedment, nail geometry, hardness and tip shape vary between nail classes.

7. Hilti systems

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Perpendicularity

Our fastening tools help to keep nails perpendicular to the working surface, thus eliminating failures caused by attempting to drive the nail at an angle.

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Nail guidance

Thanks to excellent nail guidance in the tool and the use of solid washers, the nail leaves the tool at the angle you intend.

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Fastening energy

The nail driving energy released by a Hilti tool is precisely controlled to ensure reliable achievement of the desired embedment depth.

8. Selecting the right nail for your requirements

Here are four simple steps to help guide you to the right nail:

Understand the application
Be specific about what requirements are important
Get to know the Hilti range of nails
Then choose the right nail on the basis of your requirements

Following these four steps will help you:

Maximize the stick rate
Achieve the required holding values
Select the most cost-efficient nail
Achieve optimum embedment depth based on selecting the appropriate cartridge and adjusting the power setting