HAMMERLOCK is machined from highly conductive copper.

It is easy to see why acorn clamps are more susceptible to corrosion than any other type of grounding connection.


Copper Grounding Connector

High Quality Connections

The patented HAMMERLOCK grounding connector from ERICO® connects the grounding conductor to the ground rod. Machined from highly conductive copper, the state-of-the-art HAMMERLOCK provides a low- resistance connection designed to withstand ground fault currents and lightning transients. The HAMMERLOCK connector’s mechanically rugged design will help ensure that the highest level of performance is maintained for many years after the connection has been buried in the harsh underground environment.

The HAMMERLOCK is one of the quickest and easiest grounding connectors to install and requires no special tools or training. It has been engineered to be user-friendly, cost-effective, and provides a high level of protection for people and expensive equipment.

Features Include:

  • Machined from 100% high-conductivity copper
  • Excellent mechanical strength
  • Irreversible connection
  • Fast and simple installation requires only a hammer
  • No training required
  • Provides a visual indication of completed connection
  • Allows for “T” or pass-through connections
  • UL® Listed (#2, 4 and 6 solid to 5/8” copper or galvanized rod)

The Importance of Grounding Connections

Electrical utilities and other industries are discovering significant cost benefits when high-quality electrical grounding systems are installed. Many are specifying low-resistance grounds along their transmission and distribution networks.

These low-resistance electrodes limit neutral-to-ground voltage, improve safety and provide better protection against lightning damage. In fact, the savings realized from reduced equipment damage and the decrease in service interruptions have prompted many utilities to undertake large-scale grounding improvement programs.

The three main components of the grounding system are the grounding connector, grounding conductor and ground rod. They are all equally important to the performance of the system. A loose or corroded connection will render the grounding system ineffective. While acorn clamps are still the connector of choice, many installers recognize the serious deficiency in their performance and the risks associated with poor-quality connections. Many acorn clamps are loose the day they are installed.

In order to install an acorn clamp effectively, it is necessary to know the proper torque level for the bolt. Since acorn clamps don’t come with instructions and most crews don’t have or wouldn’t use a torque wrench, many are broken or installed incorrectly. The cost of replacing damaged equipment, and the labor associated with doing so, quickly puts the cost of using inferior connectors into perspective.

Installation Costs

The actual cost of the grounding connector represents only a small fraction of the total installed expense when the labor rate of the installation crew, equipment overhead costs, ground rod and conductor costs are considered. Installation costs increase significantly when deep-driven rods are used — a common practice in grounding improvement programs.

Therefore, investing in the best-performing, longest-lasting grounding connector is a wise choice. Initially paying more for a quality connector will actually save money in the long run, by reducing downtime and eliminating the need for crews to return to the site for repairs.


Acorn clamps are utilized because they are inexpensive. They were developed before the proliferation of expensive electronics, at a time when the demand for electric power was lower and before power quality was a serious consideration. The HAMMERLOCK, on the other hand, was designed to meet the needs of today’s modern grounding programs. Therefore, an upgraded or perhaps more aptly stated, updated, grounding program specification should require a quality connector and exclude the acorn clamp.

How the HAMMERLOCK works

The ground wire is placed through the connector body and then the body is placed on the top of the ground rod. As the connector is struck with a hammer, HAMMERLOCK is connected to the ground rod using the same compression technology used in the threadless couplers that connect deep-driven rods together.

At the same time, the ground wire is locked in place as the connector plug enters the body.

Ease of Installation

Installing the HAMMERLOCK is as easy as swinging a hammer. Its intuitive design requires no special tools or training. When the large diameter on the HAMMERLOCK plug is flush or below the round body, the connection is complete and irreversible. The HAMMERLOCK can be installed three to five times faster than an acorn clamp and is easier to install in a trench.

The HAMMERLOCK provides a high-quality grounding connection that is easy to use and cost-effective — withstanding 100% of the current carrying capacity of the conductor. Given the important function of today’s grounding system, the HAMMERLOCK provides excellent connector value.

H86317-USEN Hammerlock PDF

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HAMMERLOCK vs. Acorn Clamps – A Comparison
Acorn Clamps
Its intuitive design requires no special tools or training Proper installation of an acorn clamp requires the use of a torque wrench and knowledge of proper bolt torque level
A few swings of the hammer and the HAMMERLOCK provides a complete, irreversible connection Many acorn clamps are loose the day they are installed
HAMMERLOCK installation is 3 to 5 times faster than an acorn clamp It takes longer to install an acorn clamp
HAMMERLOCK allows for 100% of the conductor and ground rod circumference surface areas to be used in the connection An acorn clamp only uses 15% of the available contact area between rod and conductor
The HAMMERLOCK provides a high-quality grounding connection that is easy to use and cost effective Acorn clamps are more susceptible to loosening and corrosion than any other type of grounding connection
The HAMMERLOCK is manufactured from high-conductivity copper – 93% IACS Manufactured from low conductivity silicon bronze – 10% IACS
With HAMMERLOCK there is visual indication of the finished connection Provides no visual indication of a completed connection unless a torque wrench is used
The HAMMERLOCK has excellent mechanical strength and a robust design Pulling on the ground conductor can loosen the acorn clamp