Impact wrench buying guide

Impact wrench buying guide

Sebastian, self-taught DIY-er, Exeter

Guide written by:

Sebastian, self-taught DIY-er, Exeter

Referred to as an impact wrench, a bolt-on or a driver: this is the must-have tool for mechanics! Designed to tighten and loosen bolts, its torquing force is expressed in Newton-meters (Nm). Powered by electricity, battery or air compressor, let's discuss impact wrenches!

Important features

  • Wired
  • Battery
  • Air compressed
  • Torque
  • Impacts per minute
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How does an impact wrench work?

An impact wrench, also known as a driver, looks a bit like a drill if you squint a bit! It is designed to bolt orunbolt bolts and screw orunscrewscrews. Especially useful for mechanics using high-torque bolting, the impact wrench is the portabletool you see being used to remove your car's wheels when you change your tires or brake pads.

Designed for clamping, any precision task will need to be finished off with a torque wrench - to make sure the head is correctly tightened. To avoid buying one driver for each different diameter, the sockets are interchangeable.Genius! The impact wrench's screwing force is driven by a strikingmechanism composed mainly of an engine, an anvil, a hammer and a spring. The driver can be electric - wired or battery powered or compressed air.

Impactwrenches and impactors differ slightly, in the following ways:

  • An impact wrench is quite literally a wrench with impacts - as the name implies, the twisting force is produces is perfect for bolting;

  • An impactor is does not necessarily have impacts - although in practice, nearly all models are impact driven.

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Compressed air

What are the characteristics of an impact wrench?

An impact wrench is selected based on different factors, the three main ones being the spiketorque provided, the impacts per minute and the power supply.


The torque is measured in Newton-meters (Nm) and represents the twisting force that will be applied to the bolting and unbolting action. To give you an idea, a wheel bearing is tightened to about 120 Nm. Consult a torque chart to get a better understanding of the required torque. Don't guess or you'll look like a tool!

Impacts per minute

The impacts per minute determines the tightening speed. The higher the number, the more torque is applied to the offending screw or bolt.

Power supply


Pretty straight forward, just have to worry about the spike torque provided and the impacts per minute.


The higher the votlage (V) and the amp hour (Ah), the more the power and autonomy the impact wrench will have. Lithium-ion (Li-Ion) batteries are commonly favored because of their rapid recharging and the lack of memory effect. Most drivers will be equipped with this type fo battery.

Pressurized air

It is important to verify that the airpressure and air flow required by the impact wrench and those supplied by the compressor match to obtain optimal use.

Other factors to help you make the right call include:

  • The tool's weight is important for better maneuverability;

  • The anvil's coating;

  • The ergonomics of the handle ;

  • A variable speed trigger ;

  • The spiking speed relative to the impacts per minute;

  • The number of batteries, when applicable;

  • The spiking torque - for maximum loosening force;

Tips for choosing and using an impact wrench

Do not attempt to use non-shock sockets as they will break on the very first impact. Those sockets are fixed via a 1/2 " square connector. Shock socketsonly!

Always plan according to the intended tasks and the recommended boltage settings to be sure to get the right torque, otherwise your impact wrench can be over or under-charged and can result in damage or frustration!

Lastly, be wary of compressedair models and verify the required pressure and flow!

More Information

For passionate mechanics, builders and DIY-lovers, follow the links below for impact wrench-related accessories, advice from our editors and more helpful guides:

Discover our impact wrenches!

Guide written by:

Sebastian, self-taught DIY-er, Exeter

Sebastian, self-taught DIY-er, Exeter

Redo a roof with wooden beams? Check. Advise everybody in the DIY shop? Check. Redo bathroom plumbing? Check. If it doesn't work, try again! I'll do my best to advise you in your projects.

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