By Noelle Lord

Higher voltage, as in the 18-volt Fein Handy- master drill, not only equates to more power but also a heavier duty tool that’s necessary for lots of large-scale boring. Photo Courtesy of Fein

Product Primer
Before you start crunching numbers for individual tools, it pays to get a handle on the variety of cordless drill types now sold.

Drill/drivers are the most common, all-purpose choice. They are equipped to accept drill bits for boring holes, as well as driver heads for fastening, and are available in models ranging from 9.6 volts to 19.2 volts to support almost any need. A drill/driver’s gears are always engaged, so when the tool strains you can squeeze the trigger harder to speed up the motor to increase torque. Or, you can switch to a lower gear (low speed) or adjust the clutch setting if you’re doing repetitive fastening.

Some applications need more mechanical advantage, such as driving in hundreds of screws as fast as possible or drilling into masonry. Because so many households now have cordless drills, manufacturers are supplying cordless tools for specialized purposes or repetitive conditions to make our lives easier.

Impact drivers (also called stick drivers) are designed for fastening. Although there are adapters for drilling, they’re not practical for this application. Impact drivers have lower voltage and are light and compact but deliver a lot of torque. They are tailor-made for “easy” fastening, such as screwing down deck boards or making and installing cabinets. Their compact size makes them easy to maneuver in tight spaces. The impact action stems from how the tool is engineered to make small
turns in rapid succession, allowing it to deliver a lot of torque—sometimes twice as much as a larger tool. Impact drivers usually have the speed control in the trigger, allowing the user to vary the power precisely.

Hammer drill/drivers add a percussion action to assist the drill/driver in going through masonry and cement. In the tool’s drive train are two gears shaped like poker chips, with teeth that work over each other to create a bouncing, up-and-down action in each stroke. In most products, you can switch the hammer action off at the clutch, thereby turning the tool into a regular drill/driver, so that it can be your everyday drill if you have masonry and light concrete work in your mix.

Sizing up the Specs
Comparing the technical specifications for cordless drills can be daunting. It’s truly a numbers game with manufacturers constantly working to outdo one another. Bigger is not always better, and some specs, such as speed and torque, are inversely related to each other. You may be making trade-offs depending on which characteristic is most important to you. Here’s a rundown of the most common specs and what they mean in practical terms.

Voltage is one of the most familiar and prominently marketed features associated with cordless tools. In simple terms, volts are the force with which electricity flows from point A to point B, and while voltage is technically only part of the measurement of electrical power (watts), it is often an indication of the tool’s brawn. The higher the voltage is, the bigger the battery pack and motor must be, resulting in a heavier (and usually larger) tool. A 12-volt or 14.4-volt drill/driver weighs around four pounds, whereas most 18-volters are more than six pounds. Big voltage is necessary if you’re doing a lot of wood or timber boring or if you want the extra power to put down 100 decking screws. For tougher or longer jobs, more voltage means the drill doesn’t have to work as hard as a lower voltage tool doing the same task. If you’re not putting the tool through its paces all day long and body fatigue is a concern, most homeowners (and many contractors) meet their needs very well with 12-volt or 14.4-volt models.

Torque is not marketed as deliberately as voltage, but it’s another critical spec to consider. Torque output in cordless tools is measured in inch-pounds and is a number that denotes the amount of force available to produce torsion or rotation—literally twisting. Ample torque is always a good thing because, whether you are boring holes or driving fasteners, you want enough twisting force to get the screw or bit into the material. The catch is each manufacturer rates torque differently. Many go for the highest number, known as ‘hard joint’ or ‘hard case’ torque—the amount of torque the tool exerts when it’s pushed to its performance limit. Most of us don’t use a tool that way. What we’re interested in is ‘soft joint’ or ‘soft case’—real-world running torque, which allows the tool to continue when it encounters resistance.

Speed, or the range of rpms (revolutions per minute), is another useful rating for sizing up the tool’s utility. Speed, however, is also an important factor in the torque capacity of a cordless drill or driver. Quality cordless drill/drivers have gearboxes with two (and sometimes three) separate speed ranges that allow the user to gear the tool up or down like a car’s transmission for mechanical advantage. Slower speed ranges are around 400 rpm to 500 rpm, providing increased torque for driving large screws or making large holes. Higher speed ranges now reach 1,500 rpm to 2,000 rpm for rapid fastening or drilling. Some specialty products and lower priced drills have a single speed range with the trigger as the only control.

Most drills also have a variable speed feature. The more you squeeze the trigger, the faster the drill spins. Variable speed is usually associated with a break that stops the chuck from turning as soon as you release the trigger. This feature allows you to get a screw or a drill bit started, helps prevent over-torquing (which can break the head off a screw), and is also nice for delicate work.

Clutch settings limit the maximum amount of torque exerted by the tool. Virtually all cordless drill/drivers now have anywhere from 12 to 25 clutch settings. They assist the user in preventing the drill from driving a screw too far into soft wallboard, mangling a screw's head by turning too fast, or breaking off a soft metal, such as brass, by forcing it through too much resistance.

Manufacturers tout that more settings mean more precise torque control. Professional users, however, often say they rarely use clutch settings and prefer to go by the feel of the tool and their familiarity with the materials. Homeowners will probably want a tool that falls somewhere in the middle. (I would make myself crazy adjusting through 25 settings!)

Chuck capacity indicates the largest diameter bit shaft that a drill's chuck can hold. Smaller (lower voltage) drill/drivers are fitted with 3/8” capacity chucks, while larger tools come standard with 1/2” chucks. Once considered strictly industrial, a modern 1/2” chuck is ideal these days because it can accommodate a greater variety of bit sizes. Many manufacturers have a ‘caming chuck’ or ‘ratcheting chuck’ that permits extra tightening of the bit, making it more dependable and stable so it won’t skip when working through resistance (using extra torque).

Weight is a hot topic of conversation when shopping for cordless drill/drivers. Although it’s primarily a function of total voltage (the higher the voltage, the greater the battery size and weight), higher power components also require more heavy-duty materials and more mass. An 18-volt powerhouse needs a larger and therefore heavier motor to support it; larger chucks (going from 3/8” to 1/2”) need more and heavier housings to control the additional torque. The newest battery technology boasts comparable weight to its lower voltage counterparts, but the tool itself must be sturdier, and therefore weighs more, to handle the additional power.

Other components to consider include product housing, switches, bearings and gears, and the motor and transmission. More professional-grade products are designed for tougher conditions and harsher use and usually have a housing that can survive at least a 10’ drop test. A dusty environment (and what old house isn’t dusty?) will take its toll on switches and motors. Many manufacturers design motor and gear housings to shield them from dust and moisture. Look for tools with heat shields and cooling fans for motors if you’re going to be running them for extended hours. A high-powered drill/driver needs a motor that won’t burn out from the additional power and a transmission to keep up with the speed. It’s worth doing some homework online or talking to the manufacturers’ technical support people to find out about the many specifications that are available and how each manufacturer’s product differs.

How Much Power?
Of course there wouldn’t be cordless tools without rechargeable batteries. Battery capacity is measured in ampere-hours (Ah) or, to use a crude analogy, the quantity of electricity that is delivered over a period of time. For example, a car battery rated at 10 Ah can deliver 10 amps for one hour or one amp for 10 hours. In cordless tools, the higher the amp-hour rating is, the longer the tool will run per battery charge. Any battery is actually a pack comprised of multiple cells, each supplying about 1.2 volts of electricity. Weight is a factor of battery size because each one of these cells adds mass. A 12-volt drill has a 10-cell battery; a 24-volt tool has 20 cells—and twice the weight. Depending on the battery technology, most battery capacities run between 2.4 and 3.5 Ah.

No manufacturer is willing to say how long a battery will last or how many times you can charge it because that depends on battery use and care. The average is 1,200 to 1,500 charge–discharge cycles. Some batteries will fail at 500; some will go to 3,000. A high quality tool will probably outlast its batteries, and then you’ll need to decide whether to buy more batteries (anywhere from $25 to $100 each, de-pending on the manufacturer) or spend $80 more and upgrade your entire drill.
It’s a shame to think we’re living in an age of disposable tools. Some manufacturers offer new tools that use older battery technology or one battery for their entire cordless line.

Other Features
The warranty says a lot about a product. The longer the warranty, the longer the manufacturer expects the tool to last without developing problems that the company will have to pay for. Many drill/drivers offer only one- to two-year warrantees and some go to three; expect different warrantees for the tool and its battery.

Repairing old houses is demanding enough that you don’t need to expend energy on a tool that’s hard to position, doesn’t adjust easily for settings or changing bits, is difficult to fit into tight spaces, or has switches that aren’t in the right places for fingers to maneuver. Assessing the ergonomics or the “hand” of a tool is important. Carefully consider how it fits your grip, balances in your hand, and whether it allows your fingers

to reach switches and the battery release easily. A comfortable grip and well-distributed tool weight will make a big difference when you’re holding a building part in one hand and trying to maneuver a drill with the other. Visit tool retailers
and actually feel different tools with different components. If possible, run the tool or one that is equivalent. On paper, a drill/driver may have perfect specs for your applications, but you may find it too powerful to control or not versatile enough for different tasks.

I saved price for last because it won’t matter if you buy the wrong tool. I prefer to buy the highest quality tool I can afford. Manufacturers making professional-grade tools run more endurance tests, often offer longer-lasting batteries with shorter charging times, and focus on ergonomics for the user’s comfort and safety. Ultimately, you want a product that feels good in your hand, is easy to use, and helps you do the best job possible around your old house, whatever that job may be.

Noelle Lord specializes in restoring building surfaces at Peter Lord Plaster and Paint and writes about the care of historic buildings from her home in Limington, Maine; irestore@adelphia.net.