Popular Woodworking 2003-02 № 132, страница 70

your work. Obviously, drilling through the side of a board, or missing the second board altogether and screwing your hand is not a recommended procedure. Also, when putting in a screw, having the screw tip angled to the screw head will strip out the head, making the screw unusable and often leaving it only halfway in the hole. (See the photo on previous page.)

Now back to drilling. If you're drilling all the way through a piece of wood, when the bit pushes out the back side of the wood, there's plenty of force pushing on a weak wall of wood fibers, and the last ¹/32" of wood ends up being torn through rather than drilled through. Using a backing board (photo at left) will solve this unsightly problem.

Sometimes your workpiece

ALL ABOUT BATTERIES

We had some questions about cordless drill batteries and went to an industry expert, Doug Bock, the group sales manager for Panasonic, for the answers. Panasonic's battery division sells batteries to many manufacturers of cordless drills and is the largest manufacturer of cordless drill batteries in the world.

When you talk about battery performance, think of the amp/hour rating like the gas tank in your car. The larger the tank (and the higher the amp/hours) the longer the drive. It's not a perfect analogy. That doesn't take into account variables in the engine and drive train (motor and gearing) that can affect performance, but it's a quick way to think of things.

Bock explained the difference between NiCad and NiMH batteries simply and in terms of performance. NiMH batteries provide longer run time in the same amount of battery "space." But because of their charging differences they require different care from the charger, making them more expensive. NiCad batteries absorb heat when charging and charge in a flat line with a quick heat spike at the end. NiMH batteries give off heat as they charge (requiring venting) in a gentle climb with a gentle peak at the end of the charge. The difference in heat spikes requires different

Blow-out, when drilling completely through a board, can be annoying and unattractive. It's also easily reduced or eliminated completely by using a backing board.The left-hand hole shows standard blow-out.The right-hand hole was made with the backing board (shown at left) and shows remarkably less damage to the surrounding wood.

One of the more clever additions to the drill bit category is the piloting/countersinking bit shown at left.Working backwards from right to left, the bit can be used as a pilot bit, combination pilot and countersink, or as a combination pilot and counterbore for use with plugs or buttons. The bit shown here uses a replaceable standard-size drill bit in case of breakage.

charging technology. Early NiMH batteries didn't fare well in NiCad chargers.

Bock also wants to dispel the "memory" rumor you hear about rechargeable batteries. It

was true at one time that if a battery wasn't completely charged the first time it would "remember" that level and recharge only that far. This is old technology and no manufacturer sells batteries with this problem. As to battery maintenance, Bock says to follow the directions. Many batteries will require between three and seven charges to reach maximum capacity. If a battery is left dormant for a month or so (even in a trickle charger) it may not perform up to capacity. By charging the battery for 24 hours (reconditioning the battery) you should get back the full performance of the battery.

One of the more important factors in extending the life of your battery is the charger.A "smart" charger can improve not only the life expectancy, but also the battery readiness. If a battery is charged while too hot (from recent use or just ambient temperature) it may not take a full charge. Smart chargers will check the battery temperature and delay charging automatically until the temperature drops.Also, smart chargers allow the battery to remain safely in the charger once charging is complete without discharging or damaging the battery. In fact the best chargers apply a trickle-charge to keep the battery topped off.

70 Popular Woodworking February 2003