Modern Power Tools - the Lithium Ion Cordless Drill

By: Amanda King

Power tools are essential for those jobs, which require more intense workmanship that ordinary tools cannot handle. A power tool is basically a tool, which is powered by an electric motor or alternatively a compressed air motor or petrol driven motor. They are typically used in the construction industry but are also used around the house to complete those otherwise hard to do jobs. Power tools are used for cutting, drilling, shaping, grinding, painting, sanding and polishing. Machine tools are a form of power tools used in metal work. It is not uncommon for the same power tool to be used both in wood and metal work.

The first used power tool was the lathe. Power tools were initially developed during the time of the industrial revolution. When factories began to use power tools to drive belts from overhead shafts. The main power source was a water wheel or later a steam engine. These tools were stationary until the introduction of the electric motor in the 1880s, which made the self powered stationary and portable tools we know today possible. The electric motor has remained the preferred source by which stationary power tools are driven. These tools use a cord but what has become increasingly popular for portable power tools is the battery. However batteries still have limitations because of they run out and lack sustaining power. Cost of buying and maintaining the use of batteries keep the cordless versions in lower demand on the market. Nailers and paint sprayers more frequently use air pressure, while chain saws, weed eaters and lawn motors have a preference for petrol driven motors.

One of the most popular power tools is the cordless drill, which is a type of electric drill but instead of being connected to a wall socket uses rechargeable batteries. Typically cordless drills come in the hammer drill configuration and mostly have a clutch setting, which allows them to be used for driving screws. In order to continue working without much interruption the tradesman will have a number of spare battery packs charging while drilling, so that he or she can quickly swap them.

The earliest cordless drills used 7.2V battery packs but over the years the battery voltage has increased to 18V and more, thus allowing these tools to produce as much torque as those drills connected to a main power supply. The main disadvantage of most current cordless drills is the use of nickel-cadmium (NiCd) batteries, which develop a "memory effect" or internal short circuits due to dendrite growth. This severely limits their usefulness and life span and in turn creates a hazardous materials disposal problem. Drill manufacturers are now producing lithium ion batteries. Makita Electric Works and Milwaukee Electric Tool Corporation are two such manufacturers producing lithium ion batteries. The main advantages are lack of memory effect and very short charging time. Lithium ion batteries can provide an hour of work per twenty minutes of charging instead of vice versa. These batteries also have a constant discharge rate meaning that the power output remains constant until the battery is depleted, something that nickel-cadmium batteries lacks. This constant discharge rate makes cordless drills much more versatile. Lithium-ion batteries also hold a charge for a significantly longer time than nickel-cadmium batteries, about 2 years if not used, vs. around 4 months for a nickel-cadmium battery.

Cordless drills will increase in their popularity as science overcomes its' limitations and as power tools become increasingly powerful.

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