Text and photos by the author.
Air (pneumatic) impact wrenches are a mainstay of any shop. However, there are times (and those times are frequent) when dragging an air hose around isn’t ideal, especially when working in a confined area, or where the air hose (straight or coiled) can become entangled or pose a tripping hazard, or when you’re concerned about dragging an air hose over a painted surface.
Especially in the case of an engine builder’s assembly room, where cleanliness is absolutely paramount, air hoses can collect and drop/drag dust and other contaminants onto engine components. Granted, any professional engine builder isn’t about to assemble an engine using a power tool (fasteners are always tightened using precision-calibrated instruments such as torque wrenches, stretch gauges and angle-gauges). However, when it comes to engine disassembly, a clean, cordless impact can provide both convenience and time-savings.
When cordless impact wrenches were first introduced to our industry years ago, they often lacked the necessary torque that many applications demand, and battery life, well, just plain stunk. Today, advances in design, materials and construction have finally met these challenges, and the Bosch cordless impact “guns” are prime examples of top-level tools that actually meet professional requirements.
For this review, I chose a sampling of three cordless impact wrenches from Bosch’s extensive lineup, including Models IWHT180, IWH181 and 24618.
Model IWHT180 is a big boy (10 inches long), offering a 1/2-inch drive, with a whopping 500 ft.-lbs. of available torque. It’s also a weighty workhorse (6.7 lbs.), with an extended “snout” for, well, extended reach (nice for high heat areas, placing your hand a bit further away from the heat source). One aspect of the drive is its flat-anvil design that features a friction ring. The socket wrench is definitely secured onto this drive nose, but you’ll have to force the socket on and off using a bit of muscle. Let’s put it this way: Once the socket is engaged to the tool, it’s not about to accidentally fall off. Considering the size, weight and available torque, this is definitely the big-gun in the cordless arsenal. I carried this guy around on a long road trip, and used it on five occasions to remove and install wheels on cars, trucks and trailers. No compressed air needed, and no generator required. Just pull it out of its sturdy case, get the job done and put it back into its case. I never re-charged the battery for a two-week period, and it never let me down. This is a real brute.
Model 24618 is a 1/2-inch drive “compact” version, punching out an impressive 1,600 in.-lbs. of maximum torque (that translates to about 133 ft.-lbs.). This gun has become one of my favorites, especially for engine disassembly. During test-fitting and clearance-checking of a 501 CID Pontiac drag engine that was equipped with main cap studs, I tightened main cap nuts (using a torque wrench) to 110 ft.-lbs. (caps 1 to 4) and 140 ft.-lbs. (cap number 5) in order to measure installed main bearing inside diameters during bearing-clearance checks. When it came time to remove the crank, I used the Bosch 24618 to remove the main stud nuts (I hadn’t even fully charged the lithium ion battery pack at this point). To my delight, this compact gun didn’t even think about arguing. I was able to zip off each nut quickly and with ease. The lightweight and compact design (along with the great ergonomic grip shape) made this chore a pleasure.
Model IWH181 features a 3/8-inch drive, in a tidy compact snub-nose package, with a maximum torque rating of 1,500 in.-lbs. (about 125 ft.-lbs.). During the restoration of a few cars in my shop, I routinely used this 3/8-inch gun to zip off a variety of bolts and nuts undercar and underhood. Eliminating the need to drag an air hose around was a nice change of pace. And unlike the rechargeable batteries that I’ve used in years past, I never ran the battery down during this work. The life of these 18-volt lithium ion batteries is really impressive!
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