Impact Wrenches: Knowing your hog rings from your detent pins

​Question: What power tool is so strong, you won't find one in your average toolbox? An impact wrench, of course! In fact, these power tools have such a high rotational torque, they will normally only be used by professionals such as mechanics and construction workers. Impact wrenches are designed to tighten and loosen nuts, bolts, and fasteners. They are very popular among tradespeople as they require minimal effort on the user's part, get the job done fast, and provide a solution when a ratchet wrench just isn't doing the trick.

However, anyone in the industry knows, when it comes to choosing an impact wrench, the big question is whether you want one with a hog ring (friction ring) anvil, or with a detent pin anvil. If you're looking to purchase one but are stuck on what the difference is, let us explain before you buy.

How do impact wrenches work?

Before we establish the difference between anvils, you’ll want to know how an impact wrench works.

Impact wrenches are used as a last resort for when you just can’t loosen that lug nut or get a grip on a screw head with an ordinary wrench. An impact wrench brings additional torque - that is, the amount of force needed to make something move - to make it possible to loosen or tighten that stubborn nut. It is not used as a replacement for a wrench - you should always try to use a ratchet wrench or breaker bar first.

These powerful tools get their torque from an electric or air (pneumatic) motor that possesses a hammering mechanism to apply sudden blows to the nuts/bolts/fasteners with strong ‘impact’. The motor then applies a constant twisting motion to the nut/bolt in quick, forceful bursts - usually around every 5 seconds - to bring movement to it.

The result is so immense that, when used in the correct manner, there is not a nut or bolt it can't shift.

What do anvils do?

The anvil is the head of the impact wrench. Its sole purpose is to hold the socket or any other add-ons in place, so that you can use the tool as intended.

It is by far one of the strongest parts of the power tool, since it has to withstand not just the force of the motor, but also the friction of the nuts/bolts/fasteners, whilst holding onto the socket in the process.

This is why it is so important to choose the right type of anvil. Depending on your job, the type of anvil you choose (hog ring or detent pin) must hold onto your sockets with ease to prevent any accidents or loss of parts in the workplace. Some jobs, such as those that involve working at a height, make it that much more imperative you choose a secure anvil.

Hog rings

So, what exactly is the difference between anvils, you ask? To begin with, hog rings (friction rings) hold sockets in place with a C-shaped pin that is wider than the inside of the socket. They have smooth sides that apply just enough pressure to hold a socket without it being a challenge to remove. In short, they slide on and off with ease - and just a tad bit of force. This makes them popular with mechanics, as they will need to use a number of different sockets for one job.

Advantages of a hog ring anvil:

• You can remove/change the sockets quickly and easily

• You can slide sockets on and off using only the force of your hands; no external tools necessary

• Great for automotive jobs or any other profession that involves changing a socket regularly

Disadvantages of a hog ring anvil:

• The socket may slide up and down when the tool is on

• It can be dangerous to use at a height due to the risk of a socket falling off

• They may increase fatigue when used for jobs involving continuous socket-changing

Detent pins

On the other hand, detent pin anvils are commonly used by construction workers or those at a height, since they hold the socket more securely than a hog ring. With a tiny pin on the side that secures the sockets in place, it cannot be removed with just your hands, but is usually pushed in with a screwdriver, thanks to an internal spring. Another method is to match up the pin with the socket hole. The idea is, since it's so fixed on, you work harder to remove the socket.

Advantages of a detent pin anvil:

• The socket will stay in place when the tool is on

• Prevents accidents as sockets will not fall off at a height or down engine compartments

• Better durability - the less you change the sockets, the longer the parts will last

Disadvantages of a detent pin anvil:

• Requires hand tools, e.g. a screwdriver, to change sockets

• Socket changes take much longer

• Less friction sliding on the socket compared to a hog ring

Hog Rings vs Detent Pins: which is better?

The most important thing to remember is that the difference between anvils is simply how they hold the sockets. This means that when you purchase an impact wrench, you should choose depending on how often you need to change the socket. It is not a matter of which is 'better', per se, but rather, which is more suited to your job.

For instance, as mentioned, hog ring anvils are deemed easier for when you need to change the socket regularly, since the sockets can slide on and off without the need for assistance tools; whereas, with detent pins, it's the opposite.

This does not mean that hog rings are better than detent pins. While some may disagree, all preferences are, of course, subjective, and would depend on what you're using the impact wrench for. In fact, we would argue that both designs are extremely effective and essential for the power tool market, as trades jobs are not a one-size-fits-all. Plus, they are almost always similar in price.

Time to buy

So, now that you've got a bit of knowledge behind you on impact wrench anvils and the differences between them, it's time to choose one for your toolbox. We recommend DeWalt's 18V XR Cordless Brushless Impact Wrench collection as a great place to start!

DeWalt DCF921D2T 18V XR Cordless Brushless 1/2" Hog Ring Impact Wrench With 2 x 2.0Ah Batteries, Charger & Case

​Up to 609 breakaway torque: This 18V DeWalt Impact Wrench has up to 609 breakaway torque (406 Nm of fastening torque) to get your jobs done as quickly as possible, as well as ensure the removal of the toughest bolts Ultra-compact, lightweight design: Use your hog ring impact wrench in tight, confined spaces, as it is super light and easy to hold. You'll find yourself using the tool all day without irregular breaks and little hand strain Square drive with hog ring: The hog ring on this cordless impact wrench allows for quick socket changes, so you can get a job done quickly without the need to spend a long time changing the socket

DeWalt DCF921D2T 18V XR Cordless Brushless 1/2" Hog Ring Impact Wrench With 2 x 2.0Ah Batteries, Charger & Case

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£247.15

Inc VAT each. Price subject to change.

DeWalt DCF922P2T 18V XR Cordless Brushless 1/2" Detent Pin Impact Wrench with 2 x 5.0Ah Batteries, Charger & Case

​Brushless motor: Cordless impact wrenches from DeWalt feature a brushless motor to deliver a high performance and extend the tool's lifespan. It also allows for a much shorter design (125mm) to make it easier to use in compact spaces Up to 609 breakaway torque: This 18V DeWalt Impact Wrench has up to 609 breakaway torque (406 Nm of fastening torque) to get your jobs done as quickly as possible, as well as ensure the removal of the tightest bolts Ultra-compact, lightweight design: Use your 18V impact wrench in tight, confined spaces, as it is super light and easy to hold. Plus, the 1/2 square drive with detent pin allows quick socket changes

DeWalt DCF922P2T 18V XR Cordless Brushless 1/2" Detent Pin Impact Wrench with 2 x 5.0Ah Batteries, Charger & Case

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£318.90

Inc VAT each. Price subject to change.

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