How to Buy a Cordless Drill
It’s rare that you’ll find a woodworking shop that doesn’t have at least one cordless drill. It’s actually two tools in one: a drill and a power screwdriver, with a two-speed gearbox that lets you select high speed/low torque for drilling and low speed/high torque for driving screws. The clutch is used for driving screws to prevent stripping out the hole or the screw.
Many woodworkers even have two (or more) cordless drills. This reduces the number of bit changes so you can have your pilot/countersink in one and your driver bit in the other. It also allows you to keep one lightweight drill and one heavyweight. The smaller and lighter-weight drills are great when you need to drill a lot of small holes or drive small screws, but you’ll need more power for drilling larger holes in hardwood.
Know the Features
What it really comes down to is finding a drill (or drills) with the power you need and the comfort you desire.
This is a personal preference. If you can, hold several drills and pretend to drill some holes with them (looking funny in the store for a few minutes will pay off with years of comfort). Is the handle comfortable, or too big, or too small? Is the head angle (the relationship of the driver to the handle) correct for you? How easy is it to change direction? In most cases, you’ll find a few that are much more comfortable to you than the others.
Higher-voltage batteries provide more power. Although more expensive, NiMH batteries appear to have a longer run time per pound than ni-cad, but the jury is still out on this one.
The ampere-hour rating, abbreviated Ah, gives you an indication of how long you can go between charges. Higher Ah ratings won’t provide any more power, but their charges last longer, generally in direct proportion to the rating number (a 3 Ah battery will last twice as long as a 1.5 Ah). Higher Ah batteries usually don’t weigh any more than lower Ah batteries.
Higher speeds drill holes faster, and usually cleaner, than slower models. Be especially careful of larger, more powerful drills, which may be geared down for heavy use and lacking the higher speeds that are better for everyday small bits.
Although a drill may seem light enough in the store, think about holding it at a difficult angle for a long period. Don’t get carried away and get the biggest, most powerful cordless drill you can afford. For one thing, it’ll weigh much more than moderate 9.6- to 14.4-volt drills. For another, when you’re working in the shop, an outlet and perhaps a drill press are right at hand for those really large holes. The lighter weight of moderate-size drills will make your arm happy for years.
The drive system should include:
1. A two-speed gearbox so you have the option of high speed or high torque.
2. Smooth speed control at the trigger so you can start screws or bits slow and then speed up (electronic speed controls, especially those that provide constant rotation speed, are particularly good).
3. An electric brake for safety and so you can move on to the next hole or screw quickly.
4. A multitorque clutch so you can apply just enough torque to drive a screw home without stripping the screw or hole.
T-handles are the most popular because they’re better balanced and fit into tight spaces easier. While you can always use a second hand behind the motor on a T-handle, a pistol grip gives you a lot of one-handed power so you can to push directly in line with the bit. Some rubber on the handle helps your holding power as well.
Need some extra power and control? An optional side handle will let you really apply some force.
With the exception of a few impact/hammer drills and some bargain-basement specials, everything’s keyless now–and it’s a good thing, too! You want one that loosens and tightens easily and that gets a solid hold on the bit. You’ll also need to decide between 1/2-inch and 3/8-inch capacity. One-half-inch chucks are necessary for some larger bits, but they weigh more than the 3/8-inch chucks. Most woodworkers choose 3/8-inch chucks.
An automatic chuck lock is a convenient feature on keyless chucks. When you turn the outer ring of the chuck to change bits it automatically locks the chuck. Makes doing this three-handed operation much easier with two hands.
If you have a need for multiple cordless tools (the flashlights that use these batteries are really great), having interchangeable batteries is a big plus. In this case, choose a drill that’s part of a coordinated line of tools.
The heart of cordless tools
The battery pack that comes with a battery-powered tool is actually a collection of battery cells, usually AA size, but 1.2-volt instead of the standard 1.5-volt AAs we use for most consumer electronics.
Batteries work by converting chemical reactions to electricity. A battery comprises two metals immersed in a liquid electrolyte. In a ni-cad the metals are nickel and cadmium. When the battery is charged, the nickel is oxidized (similar to copper turning green). When the battery is used, the nickel is reduced and the cadmium is oxidized by electron flow between the two. This flow of electrons is what produces electrical flow through the motor of a tool.
A NiMH (nickel metal hydride) battery is similar except that it uses metal hydrides instead of cadmium. Metal hydrides have the potential to produce power for longer periods than cadmium. These batteries last significantly longer in small electronic devices, such as digital cameras, but the jury is still out as to whether this holds true for higher-power applications such as cordless tools. Used NiMH batteries are not considered a hazardous waste, as are used ni-cad batteries.
Overcharging will significantly reduce the life of your batteries. A good charger won’t allow this to happen, no matter how long you leave the battery in it. Indicator lights showing when the battery is being charged, when it’s fully charged, and when there’s a problem may be important for you.
Is there battery memory?
Although there is such a thing as memory for ni-cad and somewhat for NiMH cells, it is rare that this effect is ever present. Memory only happens when a cell is continuously charged and discharged exactly the same amount in a repetitive cycle over a long period of time. The only known example is NASA’s use of ni-cad batteries on a satellite that were charged/discharged exactly the same every day by a computer. You stand a better chance of never making a single mistake in woodworking throughout your entire life than of experiencing memory effect in your power tool batteries.
Some models allow the battery to be inserted with the bulk facing forwards or backwards. This can come in handy in tight spaces.