Bosch PS40-2A 12V Lithium-Ion Impact Driver Review Cordless Drill Reviews & Impact Drivers

Bosch PS40-2A Impact Driver Review

The Bosch PS40-2A impact driver shows how a big thing can come in small package! Compact, lightweight and powerful are easy ways to describe the little impact driver that packs in 800 in-lb of screw driving torque and only uses a 12 volt Li-Ion battery to do it. With all the power of full size drill built into a unit the size of a pocket screwdriver, the Bosch PS40-2A 12V Lithium-Ion Impact Driver is a combination we needed to check out for ourselves.


With all the interest in sub-compact battery powered tools, we figured it was time we started to check out some of the offerings that are available right now. These tools are becoming popular because of their small size and high power. The Bosch PS40-2A Impactor (impact driver) is just one of these types of tools. Some of you might be wondering exactly how does an impact driver different from a drill? Good question: An impact driver is much more powerful then a drill because it gets its power from an internal mechanism that delivers hammer blows to an anvil that transmits that power to the bit. With several thousand hit or beats per minute, these tools make driving screws nearly effortless with almost no fatigue since nearly all the torque is delivered to the fastener and none to the tool operator. These types of drivers work on the same mechanical principals as the impact wrench that your auto service guy uses to take the lug nuts off your car. The exception, of course, is that these tools will just about fit in your pocket.

Bosch PS40-2A Impact Driver Build Quality

Our test tool arrived in an attractive and well decorated cardboard box. Inside the box, the tool came neatly packaged within a zippered nylon carry case. The carry case had heavy elastic and Velcro enclosures to hold the tool and accessories safely in place. The lid of the case has a clear plastic pocket for the product manuals and other literature. The trouble with this pocket is that there is no way to secure it closed, and every time we moved the case around, the instruction manuals fell out on to the floor. Along with the impact driver came a Philips and a slotted screwdriver bit, a 30 Minute Charger (Model BC430) and two Litheon (lithium-ion, get it?) 12V Max Batteries (Model BAT411).

Bosch PS40-2A impact driver kit

The fit and finish of the Bosch PS40-2A Impactor is top notch. The dark blue plastic body is sturdy, and we felt no flexing or looseness. Bosch calls the plastic material used for the exterior body housing Durashield which is made of a flexible ABS and nylon blend that is supposed to help withstand extreme use and abuse. For extra grip there are over molded rubber patches across portions of the body of the Impactor. These rubber areas also help to protect the work piece from contact with the hard surfaces of the tool like on the metal gear housing. Inside the body is a high performance frameless motor with all metal gears and a metal hammer mechanism which delivers 1,800 RPM and 3,000 BPM (beats per minute). The gears and impacting hammer are housed inside an aluminum housing with a protective rubber shield on it nose of it. Bosch claims that their “Brute Tough“ unibody power train maintains better alignment between the gearbox and motor for what they claim is the most durable drive train system on the market. All we know is that it seems to work, and work well.

Bosch PS40-2A impact driver LEDs

Bit changes are easy and fast with the industry standard 1/4″ hex drive and quick release chuck. There are a ring of three LED lights that are located on the front of the Impactor that act as a flashlight that evenly lights up around the bit when the trigger is pulled. This is a handy feature because many of the drills and impact drivers we see only have one led on the lower side of the tool that leaves a big dark spot overhead where you are often trying to line up the tool. The trigger is a variable speed type that will allow the user to adjust motor speed depending on how far the trigger is pulled. The Bosch PS40-2A Impactor feels very comfortable and balanced in the hand and is also pretty lightweight at just over 2 pounds.

Testing and Use

The first set of tests that we performed on the Bosch PS40-2A impact driver took place in the lab. Using a laser tachometer, we found the “no load” motor speed to be 1825 RPM which is actually a little higher then the specified 1800 RPM. With our noise meter it register 78 dB SPL at no load full speed and under load the noise level increased to an average level of 95 dB SPL. The upper level noise fluctuated a little depending on the fasteners we were using and the material we were trying to drive them into. All noise measurements were taking from three feet away from the impacting end of the tool.

Bosch PS40-2A impact driver dimTo demonstrate and test the impact power of the tool we took it out to a job site where a contractor was installing some kitchen cabinets. The fasteners he was using were 3” stainless steel deck screws with number 2 square drives. Now for those that don’t know this, stainless steel is a tricky material to use for fasteners because it is relatively soft and it is very common to strip out the end of the fastener making it impossible to send home or remove. We started with the upper cabinets. After finding the stud placement and predrilling our holes, we positioned them on the wall and went to town with the impact driver. The LED lights came in very handy in this application of the tool because as we were reaching inside the cabinets. With the light it was easy to see where we had predrilled the pilot holes. The Impactor was able to easily drive the 3″ screws home. The same is true of the lower cabinets too. We did not strip out a single screw head, which anyone who has used stainless steel square drive screws knows is not an easy thing to accomplish when using a regular drill. When we first started with the 12V battery, we were a little on the skeptical side as to how long they would really last on a charge and we were pleasantly surprised that we were able to install over a dozen cabinet units including screwing the faces together on a single battery (with more battery power left). For those worried about the battery life, the 30 minute quick charger helps to eliminate that problem since it will probably be able to charge the batteries faster then you can wear them down.

Bosch PS40-2A impact drivercabinet

Bosch PS40-2A impact driver drillingJust to further push the tool, we figured we had to try a few more crazy stunts. One of the tests we did was to put a 3/4″ Irwin spade bit with a 1/4″ hex drive into the Impactor and see what we could do. We chose the spade bit because it takes more effort to make a hole with one then a regular style drill bit. Again, the Impactor was able to drill several holes though a 2×4 without seeming tired. Our last field test involved driving some 3″x1/4″ lag bolts in to a piece of pine. First off we started by drilling a pilot hold with a 1/8″ bit. Needless to say, the Impactor drove the fastener in with no trouble at all, all the way up to the head. Next we took the same fastener and sent it home in the same piece of wood without a pilot hole – and got the same results. While it is not as fast as some of the 14.4 or 18-volt models we have tested, it got the job done well enough to make this a truly handy tool. On the practical side we really did love the power to size factor. With a carpenter tool belt on, we were able to comfortably carry it in one of the pouches with out it falling out or feeling too heavy.



With all the power of a full size drill built into a unit the size of a pocket screwdriver, the Bosch PS40-2A impact driver is a 12V tool with a winning combination. At the end of the day, for the guy that has to have the best, Bosch is probably a good choice. One of the other fantastic features of this impact driver (along with many of the Bosch power tools) is their three year ProVantage Tool Protection Plan which means that for the first year that you own the tool, they will replace it guaranteed, and in the second and third years that you have it, they will replace any parts worn under normal use free of charge. If that isn’t good enough, they will give you free replacement batteries, within 48 hours for the first two years you own the tool! We gave this tool a Performance Rating of 9/10 because it demonstrates an amazing amount of power in such a compact size with some great extra features. For our Value rating we gave it an 8/10 because despite its awesome performance, it is a little on the pricey side.

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