Power Tools: Drills
The basic power tool is the electric drill. In its simplest form it can accept a variety of attachments, to increase its versatility, but it may not always be designed for really hard work and difficult jobs. Too often, the drill is blamed because its limitations have not been observed.
It is wise to buy the best equipment you can afford and take advantage of the greater versatility and ability to tackle those jobs for which the better drill is designed.
All power drills basically consist of a compact electric motor in a shell – very often of high-impact plastic-with the electric motor double insulated for safety. Most drills operate on mains voltage and connect to a suitable power point with a three-pin plug.
At the ‘business end’ of the drill a chuck is mounted. This is opened and closed by a key, which should always be kept in a safe place or clipped to the cable of the drill. New keys can always be bought if you do lose one.
Chucks are made in a variety of sizes. The most usual are 6mm, 8mm, 10mm and 13mm. The larger, taking bigger attachments, are intended for the more powerful drills. Motors are up to Ahp (373W) in power and cooled with a fan.
The drill needs little maintenance beyond occasional replacement of motor brushes and the blowing out of any accumulated dust in the ventilation apertures at the rear. A drill with a 10mm chuck meets most domestic needs.
The less sophisticated drills run at a fixed speed-usually around 2,800 rpm. At these speeds, there is a limitation on the work the drill can do. For greater versatility invest in a twin or multi-speed drill.
These run between speeds of around 900 rpm to 3,000 rpm. The slower speed is essential for drilling holes in hard surfaces. These two speeds cover most requirements. The speed is simply changed by a speed selector on the drill.
For drilling really hard surfaces, such as concrete, stone, hard brick and cement, a drill with a hammer action is needed. If you contemplate drilling in hard surfaces frequently, you would be wise to buy such a drill, or obtain a percussion attachment for a standard drill. The hammer action can be switched out and the drill then becomes an ordinary two-speed drill.
This percussive action is only used when hard masonry is being drilled. This hammer action is almost imperceptible in use; as the drill rotates it also percusses at high speed to penetrate the surface.
A special percussion bit should always be used and not an ordinary tipped drill bit, which is not designed for such work.
While a hammer attachment can be fitted to any standard, if it runs at a high, fixed speed it is not suitable for drilling hard surfaces. You would need, in addition, a speed-reducing device if this is not part of the attachment.
Apart from variable-speed drills, speed reducers can turn a fixed-speed drill into a multi-speed one.
Another device which reduces speed is the right-angled speed reducer which fits into the chuck of the drill.
10. November 2011 by admin
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