Our rig combines the front wheel of a car/truck with a weighted sled like those typically seen at tractor-pulls. Although our STR TorQ-O-Matic 5000 testing rig results may not provide a number you can brag about, it does a great job at providing work that levels the playing field on these high torque cordless impact wrenches. As the impact wrench turns the rotor, the weight moves further up the ramp, providing more clamping force on the rotor via the caliper.
I definitely like the mobility of the electric impact, as a road mechanic it’s a lifesaver. That being said their’s nothing like being able to call in for some air support. I’ve had several air impact wrenches throughout the years, from 3/8″ up to 3/4″. I’d have to say Ingersoll Rand makes the best product. Their line of composite guns is my favorite by far. All the torque you need, without all the weight associated with some older models.
open-end wrench open-ended spanner A one-piece wrench with a U-shaped opening that grips two opposite faces of the bolt or nut. This wrench is often double-ended, with a different-sized opening at each end. The ends are generally oriented at an angle of around 15 degrees to the longitudinal axis of the handle. This allows a greater range of movement in enclosed spaces by flipping the wrench over. common
In operation, a rotating mass is accelerated by the motor, storing energy, then suddenly connected to the output shaft (the anvil), creating a high-torque impact. The hammer mechanism is designed such that after delivering the impact, the hammer is again allowed to spin freely, and does not stay locked. With this design, the only reaction force applied to the body of the tool is the motor accelerating the hammer, and thus the operator feels very little torque, even though a very high peak torque is delivered to the socket. (This is similar to a conventional hammer, where the user applies a small, constant force to swing the hammer, which generates a very large impulse when the hammer strikes an object.) The hammer design requires a certain minimum torque before the hammer is allowed to spin separately from the anvil, causing the tool to stop hammering and instead smoothly drive the fastener if only low torque is needed, rapidly installing/removing the fastener.
You need a good a battery to power all though which is why Craftsman have bundled a top quality one in this impact wrench kit. It is a Lithium-Ion battery for superior performance (always good to see) and is rated at a phenomenal 4ah. That means it can deliver the juice to run the tool for hours on end – because what’s the point of having an outstanding tool like this if it is sat on the bench half the time waiting for a battery charge?
Adjustable Wrenches. These tools have one stationary jaw and one adjustable jaw that can fit a variety of different nut sizes. When you use an adjustable wrench, make sure you’re turning the tool toward the adjustable side, putting pressure on the stationary jaw. This will prevent you from stripping or rounding your fastener. These wrenches are a great choice for any toolbox because you’ll always have the wrench size you need. 
Various methods are used to attach the socket or accessory to the anvil, such as a spring-loaded pin that snaps into a matching hole in the socket, preventing the socket being removed until an object is used to depress the pin, a hog ring which holds the socket by friction or by snapping into indents machined into the socket, and a through-hole, where a pin is inserted completely through the socket and anvil, locking the socket on. Hog rings are used on most smaller tools, with through-hole used only on larger impact wrenches, typically ¾" drive or greater. Pin retainers used to be more common, but seem to be being replaced by hog rings on most tools, despite the lack of a positive lock. ¼" female hex drive is becoming increasingly popular for small impact wrenches, especially cordless electric versions, allowing them to fit standard screwdriver tips rather than sockets.
Where the Ingersoll Rand did suffer a bit is in the feature set area. This is where the age of the tool showed. There is no worklight, it’s only a single speed/mode, and it has a brushed motor. We would love to see a remake of this gun, using the great features as in our review of the Ingersoll Rand W5132 Cordless Impact Review. If Ingersoll Rand will release a new 1/2” high torque, with a brushless motor, multi-speed features, and the halo LED worklight, then first place may be much closer.
Sockets and extensions for impact wrenches are made of high tensile metal, as any spring effect will greatly reduce the torque available at the fastener. Even so, the use of multiple extensions, universal joints, and so forth will weaken the impacts, and the operator needs to minimize their use. Using non-impact sockets or accessories with an impact wrench will often result in bending, fracturing, or otherwise damaging the accessory, as most are not capable of withstanding the sudden high torque of an impact tool, and can result in stripping the head on the fastener. Non-impact sockets and accessories are made of a harder more brittle metal. Safety glasses should always be worn when working with impact tools, as the strong impacts can generate high-speed shrapnel if a socket, accessory, or fastener fails.

Impact wrenches are available in all sizes and in several styles, depending on the application. ¼" drive wrenches are commonly available in both inline (the user holds the tool like a screwdriver, with the output on the end) and pistol grip (the user holds a handle which is at right angles to the output) forms, and less commonly in an angle drive, which is similar to an inline tool but with a set of bevel gears to rotate the output 90°. ⅜" impacts are most commonly available in pistol grip form and a special inline form known as a "butterfly" wrench, which has a large, flat throttle paddle on the side of the tool which may be tilted to one side or the other to control the direction of rotation, rather than using a separate reversing control, and shaped to allow access into tight areas. Regular inline and angle ⅜" drive impact wrenches are uncommon, but available. ½" drive units are virtually only available in pistol grip form, with any inline type being virtually impossible to obtain, due to the increased torque transmitted back to the user and the greater weight of the tool requiring the larger handle. ¾" drive impact wrenches are again essentially only available in pistol grip form. 1" drive tools are available in both pistol grip and "D handle" inline, where the back of the tool has an enclosed handle for the user to hold. Both forms often also incorporate a side handle, allowing both hands to hold the tool at once. 1¼" and larger wrenches are usually available in "T handle" form, with two large handles on either side of the tool body, allowing for maximum torque to be applied to the user, and giving the best control of the tool. Very large impact wrenches (up to several hundred thousand foot-pounds of torque) usually incorporate eyelets in their design, allowing them to be suspended from a crane, lift, or other device, since their weight is often more than a person can move. A recent design combines an impact wrench and an air ratchet, often called a "reactionless air ratchet" by the manufacturers, incorporating an impact assembly before the ratchet assembly. Such a design allows very high output torques with minimal effort on the operator, and prevents the common injury of slamming one's knuckles into some part of the equipment when the fastener tightens down and the torque suddenly increases. Specialty designs are available for certain applications, such as removing crankshaft pulleys without removing the radiator in a vehicle.
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