Source: TOOLS OF THE TRADE Magazine
Publication date: August 8, 2011
My main goal was to determine what subcompact cordless tools can and can't do for pro users. Everybody knows they can drive cover-plate screws without breaking a sweat, but what are their limits? To find out, I performed power, speed, and runtime tests. The results made it clear that most of these tools – despite their small size and light weight – are surprisingly capable.
Pro-grade subcompact tools were made possible by the development of lithium-ion batteries and efficient motors. Regardless of how they're labeled, the battery packs for these tools are 10.8 nominal volts, because they contain three 3.6-volt cells. The rest of the world refers to subcompacts as 10.8-volt tools. In the U.S., their 12-volt designation is accompanied by a disclaimer stating that this value is reached only at the cells' maximum point of charge.
I put the drill/drivers and impact drivers through separate torture tests, which involved drilling thousands of holes and driving thousands of screws and lags into test planks (the "torture" was mostly to my elbows and wrists). The planks consisted of multiple layers of OSB glued together to create a substrate that was more uniform than framing lumber.
Drill/drivers. I tested the drill/drivers a couple of different ways, first by driving successively longer screws into the test planks and later by replicating the torque testing done in a lab.
The first test was very straightforward – the kind of thing a carpenter might do when trying out tools. I discovered that all of the tools could sink 3-1/2-inch coarse-thread and 4-inch fine-thread screws in low gear, but it was a struggle for the weakest of them. Shorter, 3-inch coarse-thread screws would be a comfortable maximum for any of these tools – the strongest of which can drive them in high gear, too.
Torque testing. There are two torque specs for each of the drill/drivers in this article (see the individual spec boxes): one from the manufacturer ("Rated Torque" in the specs) and one from my own testing ("PTI Torque"). I performed my own tests because the manufacturers do not adhere to a common test standard, which means that their numbers cannot be used to make comparisons between brands. In 2008 an industry trade group called the Power Tool Institute (PTI) developed a common standard for torque testing, but most manufacturers don't use it.
I borrowed an Electronic Torque Tester (ETT) from CDI Torque Products (the model specified by the PTI) to do my testing. As much as possible, I followed the PTI test procedure, with one major difference: PTI says to test five of each model and I tested only one of each.
I tested each tool in the same manner – by securing it to a sliding frame, connecting it to the ETT, and running it until it stalled. The ETT then displayed the maximum torque output.
I did eight tests per tool and threw out the high and low numbers. I have a lot of confidence in my results: Porter-Cable provided a PTI rating for its tool, and it was within 2 inch-pounds of the number I got. Also, the results squared with my experience using the tools: The models that feel the most powerful scored at the top of my torque test.
Impact drivers. I couldn't get the right equipment to torque-test impact drivers, so the spec boxes in this article contain only manufacturer-provided torque ratings for these tools. As a substitute for torque testing, I timed how long it took each impact tool to drive Simpson Strong-Tie SDS lags into test planks. The top five performers are close in terms of driving speed, but there's a noticeable fall-off after that (see the bottom chart below).