Impact wrenches are powered socket tools, powered by compressed air or electricity, they are one of the most common and useful tools in both the professional, and serious amateur workshop. Impact wrenches work by spinning a "hammer" to a high speed, and then suddenly engaging the socket, to deliver a sudden burst of torque. While electric (both mains and cordless) and hydraulic models are available, it is the air impact wrench which is by far the most popular.
Air impact wrenches are by far the most popular of all air tools, and if you're doing any serious amount of automotive work you'll definitely want one. Before you rush out and make a purchase however, there are a couple of considerations - power source, and socket size. Power source will depend on your budget, and what tools you already have. Socket size will depend on the type of work you're doing.
As already mentioned, air impact wrenches are by far the most popular, but that doesn't mean they are your only choice. While they are relatively inexpensive, and offer good power, they do need a compressor as a power source. Unless you already have a suitable compressor that will add a considerable amount to the cost of the tool. If you don't have a suitable compressor, and are doing only occasional or light automotive work (such as in a home workshop) then an electric or cordless wrench is probably a better bet. These days the cordless wrenches are more than capable of light work, and are reasonably priced.
Your other main choice will be socket size. Most impact wrenches are available in sizes from 1/4" to 2" and even larger. For the home workshop a 1/2" is usually sufficient, with a 1" drive being more suitable if you're working on SUVs or light commercial vehicles. If you're working on big rigs then a 2" drive might be needed. Larger than 2" is normally only used for industrial purposes.
There is one other choice to me made, and that is style. The smallest wrenches are shaped like a screwdriver, but they are only capable of delivering low torque. Most 1/2" wrenches are of the "pistol grip" variety, shaped like an electric hand drill. As you move up to heavier duty tools you'll start to come across D and T grips which allow for a much firmer hold, and so much higher torque levels.
Few Advantage of Impact Wrench are as following-
1 Exclusive Through-bolt Construction Reduces Replacement Costs
Steel front/motor housing/handle are clamped together by four high-strength steel bolts. This exclusive feature provides better tool performance and eliminates stripped threads and loose inserts in motor housing.
2 Positive Oil-foam Lubrication System Reduces Major Cause of Impact Wrench Maintenance
Impact Wrenches feature a unique oil-foam bath that provides positive lubrication for the hammer, anvil and other working parts.
The system is designed so that if the impact mechanism runs low on oil, the tool will stop running which eliminates one of the major causes of impact wrench failure: lubrication. By simply refilling the oil reservoir, the tool can be returned to service.
3 Patented Heavy Duty Telescoping Impact Mechanism
The smooth-hitting telescopic impact mechanism is patented and has only three major parts: hammer, anvil, and rotor. These combine to provide power directly to the fastener. The hammer is splined ot the inside of the motor, which then impacts directly on the anvil and delivers more power per blow while also reducing weight and shock to the operator.
4 Patented Positive Lock Socket Retainer
With a variety of shut-off and non shut-off pulse tools to choose from you're sure to find just the right pulse tool for your job.
The correct style for you will depend on the type of work you'll be doing, so take that into consideration when making a purchase.