Impact wrench buying guide

Impact wrenches: A guide to bolt the options together

Impact wrenches are used for undoing and tightening bolts. Impact wrenches are used when no other tool can give enough force. They can also be called impact guns, air guns, air wrenches, rattle guns and torque guns.

They are generally used for the automotive industry, heavy machinery maintenance, steel construction and scaffolding. They rotate and, at the same time, apply great force in the rotation direction.

• Standard chuck impact wrench: These power tools have a square chuck that hold the sockets in place by means of a ball bearing that protrudes from the chuck itself. This is the more common chuck type.

• Hog ring impact wrench: Hog ring impact wrenches have a hole and rubber ring that hold the socket in place. They still have a square fitting so standard sockets can also be used. On these machines, the socket fits onto the chuck and then a split pin is fed through the socket and the chuck holding it in place. The rubber ring is then placed around the socket to stop the pin coming out during use.

Key Considerations When Buying An Impact Wrench

Some of the key considerations when looking to purchase an Impact wrench are:

Power: Power, measured by torque, is one of the main considerations when choosing an Impact wrench. Torque is measured in Newton metres (Nm). The higher the number, the greater the force. Impact wrenches range in power from 100Nm up to, and above, 1000Nm.

Unlike most other drills, impact wrenches have an additional function when undoing bolts, which is referred to as 'breakaway' or 'nut busting' torque. This is when an impact wrench uses an initial burst of extra power to loosen a particularly tight bolt (perhaps as a result of rust), before continuing to use the machines standard torque for the remainder of the loosening. The machine applies this automatically. Breakaway torque is also measured in Nm, although it likely exceeds the impact wrenches' standard torgue. For example, a 1000Nm impact wrench can have a nut busting torque of 1700Nm.

Impact wrenches are very powerful, so care needs to be taken during use to prevent bolts from being sheared off and to prevent materials from being damaged.

Size: The size of an impact wrench is mainly down to the bolts it will need to undo and the torque that is required.

For example: A 1005Nm impact wrench (a large tool) will work with M12 to M30 bolts (M12 = 12mm diameter, M14 = 14mm diameter etc.). A 280Nm impact wrench (medium size) will work with M8 -M16 bolts. The smaller compact 180Nm tool will work with M8 - M16 bolts.

As such, it is very important that you choose the correct impact wrench for the size of the bolt that needs to be tightened or loosened.

Speed: Some impact wrenches have a selection of speeds. Increasing the speed setting on an impact wrench will also typically increase the power (torque). Having the ability to change the speed setting on an impact wrench is useful as it can help to prevent damaged caused from the use of too much force.

Power source: The majority of impact wrenches are cordless. The main voltage used is 18v but some are available in 12v. There are some mains powered impact wrenches available (primarily in 110v for site use). These are good if you need sustained power all day long but generally aren't as powerful as their cordless counterparts, due to the recent advances made in li-ion battery technology. 18v is the most popular choice of impact wrench as they can produce almost twice as much torque as the corded options. They usually come with two batteries, so while one is charging the other can be used. It also allows for a greater scope of movement while performing the job in hand.

Chuck type: There are only a few different chuck sizes available for impact wrenches, which are are all square. They come in 3/8", 1/2", 3/4" and 1" sizes. The chuck sizes correspond to the impact sockets you have available, or wish to use on the machine.

Application: Steel works will usually require very heavy duty robust impact wrenches with a high torque output. Car industries typically use cordless 18v impact wrenches, which are very common among tyre companies for removing wheel nuts.

Some impact wrenches are suitable for scaffolding but these don't require a high torque output. Most manufacturers will state whether an impact wrench can be used on scaffolding or not.

Impact wrenches can be used around the home to tighten various bolts, but make sure that you don't use too much torque as this could result in damage.

Extras: Most of the bits used with impact wrenches will be impact sockets. You shouldn't use standard sockets as these are more susceptible to breaking and are not designed for high power. The bits designed for use with impact wrenches are far stronger. Look for impact sockets or impact socket kits. There are a variation of bits so you need to ensure that you get the correct fitting for the square drive size you have.

Impact Wrench Safety

Impact Wrenches are extremely powerful machines and can cause a lot of damage if not used properly.

Ensure the device is switched off when not in use. To do this, remove the battery or unplug the tool. This should also be done when changing bits on the power tool.

Read the manual and understand how it works. Even for an experienced user, when getting a new power tool, it is always a good idea to read the manual to ensure that you are familiar with the modes of operation and the features of the tool. This will also ensure that you get the best performance from your machine.

Grip the machine tightly. Impact wrenches can create a lot of twisting force. If you do not hold the machines tightly it could sprain or damage your wrist. Take care during use.

Wear the right clothing and protective gear. You should wear googles when using an impact wrench in case anything breaks off during use. As with most power tools, gloves should be worn.

View our range of Impact wrenches and find the lowest prices online at Howe Tools.