What is an Impact Wrench? Top 5 Milwaukee Cordless Impact Wrenches

Looking to buy a new impact wrench, but you are unsure what is the best one you can get? This buying guide aims to help you make an informed decision and purchase the right impact wrench for your needs. Thus, we will go through a few different points to ensure you’ve got it all covered!

What is an impact wrench?

An impact wrench is a socket wrench power tool producing high torque output with minimal user effort by storing energy in a rotating mass and delivering it to the output shaft. An impact mechanism consisting of an anvil (output shaft), a hammer (impactor), and a spring, helps with the process. This mechanism allows the wrench to tighten and untighten as necessary. The tool collects energy by the hammer cage over one or more revolutions, and once the hammer hits the output shaft (anvil), it creates the tightening or untightening torque.


Impact Wrenches are primarily used in the automotive industry, but they can also find an application in other sectors. For example, in construction projects, the assembly and maintenance of heavy machinery and any other instances where a high torque output is needed.


Power Supply

Air (pneumatic)

The most popular power source for an impact wrench is compressed air. These tools are more powerful and deliver better ergonomics than electric tools. They have a lower maintenance cost, and if well maintained and lubricated, pneumatic tools can be used continuously 24/7. However, to use an air impact wrench, you would require a compressor.

Corded electric

With corded impact wrenches, you will have power all day long without worrying that you will run out of battery. Corded tools offer extremely high-power output and are usually lighter than cordless equivalents as they don’t use heavy batteries, saving you money in longer terms.

However, the long, trailing cables that come with corded tools can sometimes be hazardous and lead to an injury. Moreover, you may not always have access to a power supply, and it is time-consuming to set up the transformer needed on site.

Cordless electric (battery-powered)

Since the arrival of the cordless impact wrench in the mid-2000s, corded and air impact wrenches have become less popular. Cordless impact wrenches don’t have the additional requirements of air compressors. They also offer better mobility and agility than corded impact wrenches and can be used in confined, hard to reach spaces.

Motor Type (Brushed or Brushless)

Brushless motors offer a longer runtime, better performance, and lower maintenance cost, as you don’t need to change the motor brushes when they get worn down. Read more about brushless vs brushed motors on our  Drill Buying Guide.


The torque of an impact wrench is measured in Newton Metres (Nm). The higher the torque, the more twisting force the machine can produce. There are impact wrenches with multiple torque settings, which allows you to adapt the torque output to the application. Impact wrenches with a hog ring socket offer a more efficient torque supply.

Impacts per minutes

The impact per minute affects the tightening speed. The greater the number, the more torque is used on the screw or bolt.

Body Style

Inline vs Pistol Shaped Impact Wrench

The body style is essential when you choose a cordless impact wrench. Cordless impact wrenches come in two body shapes – inline and pistol grip. The inline body looks like a large screwdriver with a grip behind the hammer and anvil. While the pistol-grip body is shaped like a handgun, and the grip is positioned beneath the motor. Inline wrenches are smaller; thus, they work best in tight spaces where you cannot fit the bigger pistol-shaped wrench.

Socket Size

The socket size is another vital feature of the impact wrench. Socket sizes are designed to fit specific nuts and bolts sizes. Furthermore, only particular socket sizes work with each impact wrench shape. For example, a ¼” socket is used with both inline and pistol wrenches, but ½” and ¾” sockets are used only with pistol-shaped wrenches.

Best range on the market

According to various sources, the M18 Fuel Mid-Torque Impact Wrenches are the best cordless impact wrenches on the market. They are incredibly compact and lightweight and offer high-quality performance like that of high-torque models thanks to fastening torque up to 550 ft-lbs and nut-busting up to 650 ft-lb.

The Milwaukee M18 Fuel Mid-Torque Impact Wrenches are available with a 3/8” square friction ring (M18 FMTIW2F38-502X), ½” square friction ring (M18 FMTIW2F12-502X), or 1/2“ square pin detent styles (M18 ONEIWP12-0).

Top 5 Milwaukee Cordless Impact Wrenches

M18 FMTIW2F12 18V 1/2″ Mid-Torque Impact Wrench

M18 FMTIW2F12 18V 1/2" Mid-Torque Impact Wrench

M18 FMTIW2F12 is the most versatile cordless impact wrench from the Milwaukee range with an industry-leading performance at 881 Nm of nut-busting torque and 745 Nm of fastening torque and an incredibly compact design, with only 152 mm overall length ideal for applications in tight spaces.

M18 ONEIWP12 Fuel One-Key 18V ½” Mid-Torque Impact Wrench

M18 ONEIWP12 Fuel One-Key 18V ½” Mid-Torque Impact Wrench

M18 ONEIWP12 is the equivalent of M18 FIWP12 but with ONE-KEY™ technology. With the ONE-KEY™ the tool can be connected with Milwaukee’s ONE-KEY™ App for complete tool customisation, allowing you to tune the tool to your needs. The ONE-KEY™ app also provides an inventory function for managing your entire tool/equipment fleet. M18 ONEIWP12 has four modes of operation thanks it’s unique Milwaukee® DRIVE CONTROL™:

M18 ONEFHIWF34 18V Fuel One-Key 3/4″ High-Torque Impact Wrench

Milwaukee M18ONEFHIWF34-0X 18V Fuel 3/4" High Torque Impact Wrench (Body Only)

M18ONEFHIWF34 is the best seller from our Milwaukee Impact Wrenches range. It delivers 1627 Nm of fastening torque in a compact size of 213 mm. Similarly to M18 ONEIWP12, the tool has a 4 -Mode DRIVE CONTROL™ which allows the user to shift into four different speed and torque settings to maximise application versatility. Mode 4- “Bolt removal” provides a maximum nut-busting torque of 2034 Nm then turns to 750 rpm for unmatched control when removing fasteners.

M18 ONEFHIWF1 18V Fuel One-Key 1″ High-Torque Impact Wrench

Milwaukee M18 ONEFHIWF1-0X 18V Fuel One-Key 1" Impact Wrench in Case (Body Only)

The M18 ONEFHIWF1 is the most powerful amongst the Milwaukee Cordless Impact Wrenches. It is the world’s first cordless 18V 1″ high torque wrench and it delivers the incredible 2,033Nm of fastening torque at half the size and weight of AC, petrol, or pneumatic solutions.

M18 ONEIWF38 18V Fuel One-Key Compact 3/8″ Impact Wrench

Milwaukee M18 ONEIWF38-0 18V Fuel One-Key Compact 3/8" Impact Wrench with Friction Ring (Body Only)

M18 ONEIWF38 is the same as M18 FIWF38 but with ONE-KEY™ technology. It is the most compact cordless impact wrench in its class, delivering the most access in tight spaces, with a performance at 339 Nm of fastening torque.

See our  FULL RANGE of Milwaukee Impact Wrenches
If you have any more questions, please do not hesitate to contact us on 01358 726719 or at admin@toolden.co.uk