No matter whether you are a retail tire dealer who offers automotive service or a commercial tire dealer who focuses on the needs of truck tire users, the odds are you have an impact wrench or three in your shop and service trucks.
Although these tools make the technician's job easier and faster to perform, they are probably the most used and abused as well as the most taken for granted. The fact that these tools are critical to keeping wheels on and people safe sometimes gets forgotten.
While most technicians are in favor of ``more power,'' the selection of the proper impact wrench for the job is essential. In order for the proper torque to be achieved during wheel installation, the impact wrench must be capable of doing this work-but not of ``overdoing'' it.
There are many impact wrench types from which to choose-whether you are servicing automobiles with 1/2-inch impact wrenches or truck wheels with 3/4-inch or 1-inch impact wrenches.
In most parts of the world, truck tire service is performed using a 3/4-inch-drive impact wrench, while the 1-inch drive is preferred and commonly used here in the U.S. and Canada. There are, however, a few fleets in the U.S. that have opted to use the 3/4-inch-drive wrench so that they avoid applying too much torque to the wheel fastening system.
Impact wrenches should be selected on the basis of the torque needed to service the wheel system being worked on. You can choose from wrenches that have varying ranges of operating torque, are designed for high-production work, have multiple speeds, put out more power in one direction for fastener removal and less in the other for fastener installation, and have extended anvils to reach lug nuts in deep truck wheels.
Some units are designed for tire-service use while others are designed for working on shocks, springs and front-ends. You can select ``standard-duty'' or ``general-duty,'' ``heavy-duty,'' ``extra-heavy-duty'' and ``super-duty'' wrenches too.
However, the working torque range is the factor that is the most important when deciding what to buy.
Impact wrenches that produce excessive torque can over-torque nuts, break studs, damage wheels and can result in wheel separations. An impact wrench must be selected that also will accommodate the size of the nuts used.
It is recommended that a heavy-duty or extra-heavy-duty tool be used for truck wheel installation applications. The key is to select the tools that best fit your needs.
Once you have the impact wrench ideally suited to your service work, proper care and maintenance is vital for it to consistently deliver maximum performance throughout its life. Pneumatic tools use compressed air as their lifeblood. The system that delivers the air must be free of moisture and any other contaminants or debris.
Compressors can be equipped with air dryers to reduce the moisture in the air lines, but they still should be drained periodically. Moisture separators and filters also must be installed and should be drained daily as well.
The line that leads directly to the air tool should have a filter to strain out dirt and debris, a pressure regulator to control the air to the tool and a lubricator to ensure the air tool's components are oiled as it works.
Removing the moisture from the air line is critical to the health of an impact wrench. Moisture is the leading cause of failure in impact wrenches. The components primarily affected are located in the motor housing, which includes the cylinder, rotor, vanes and end plates. These parts depend on a clean and dry source of compressed air.
If moisture enters the cylinder assembly, rust, corrosion and pitting will attack the components. There are no seals or gaskets between the cylinder and end plates, so the surfaces must be clean and smooth in order to maintain torque output.
Having too much or too little air supplying the wrench also is bad.
The wrench becomes either hyper or anemic. Operating wrenches with too much air pressure causes O-rings and valves to rapidly deteriorate. Usually the throttle valve is the first component affected. This valve is either steel or plastic and is linked to the trigger to control the flow of air through the wrench. High pressure causes this valve to wear at a much faster rate.
Operating an impact wrench with too little air underpowers the tool. It will not have enough energy to operate in its torque range and you'll end up with loose wheels.
With all the attention you pay to the impact wrench, don't neglect your shop's air compressor.
It is very important that the compressor your shop uses is adequate for the facility's needs and that the output of the compressor is checked on a regular basis. The compressor must be able to supply each air line with enough pressure to operate the tools and equipment in their working torque range.
Air leaks can rob the system of power to air tools and can be very expensive in terms of energy loss, since the compressor will have to work harder, as well as wheel loss when fasteners cannot be tightened to the proper torque. Therefore, all leaky fittings, nipples, couplers and hoses should be replaced immediately.
Proper hoses and fittings are essential for top performance of impact wrenches as well as other air tools. Should the wrong piping and fittings be used, an otherwise adequate compressor can be choked.
Hoses should be connected securely by installing appropriately sized quick-change chucks.
Impact wrenches with a recommended operating pressure of 90 psi must have an air system that supplies this pressure while the tool is running.
To ensure that the impact wrench is getting the proper running pressure, install a tee fitting with a gauge attached to it at the air inlet of the gun and attach the hose to other end of the tee fitting. Measure pressure when the impact wrench is running. The gauge should read 90 psi.
When the tool has stopped, air pressure in the line may be substantially higher.
Regularly checking the running pressure also can assist in detecting any restrictions in the air lines which commonly occur if the air lines are run over by vehicles or debris gets in the air system.
Impact wrenches should be checked in both directions on a regularly scheduled basis to ensure their output is correct. This can be done in a couple of ways.
First, install a wheel nut on a vehicle using the impact wrench. Measure the torque on the nut using a torque wrench in the tightening direction. If working range torque is not achieved, the impact wrench will need to be inspected and probably rebuilt. Or, you can just send the wrench out to a service center to check torque and bring the tool to its original performance capacity.
When installing a whip hose directly onto the impact wrench, do not use Teflon tape-it can flake loose and lock up the motor. Instead, use a liquid pipe sealant to prevent damage to the housing. Couplers should not be used at the wrench's air inlet, where they increase overall bulk, put an unnecessary strain on the inlet threads and deteriorate rapidly due to vibration. Use the recommended air hose and coupling assembly shown in the manufacturer's parts list.
When impact wrenches are not in use, such as at night, they should be cleaned, lubricated and stored in an area where they will not collect dirt or moisture. It is recommended that a liberal amount of air tool oil be poured in the inlet. Then run the tool before storing it. However, check the tool's parts list for the amount and type of lubricant needed and add only the amount specified.
If the impact wrench has a sealed oil-lubricated clutch, it will lose power if overfilled. Do not use air tool oil with detergent since the detergent causes the vanes or rotor blades to hang and become pitted. It also eats through the throttle valve and other small parts. Using oil with detergent is the second most common cause of shortened impact wrench life.
Impact wrenches should never be dropped, thrown, dragged around by the hose or left where they can be run over. It's best to use protective covers on all your impact wrenches to reduce damage from being abused or accidentally dropped.
In normal use in automotive repair shops and in truck tire service, impact wrenches are eventually going to wear out. However, if the air is free of moisture, is at the correct pressure and the tool is properly maintained and cared for, impact wrenches will deliver maximum performance for a longer period of time.