Power drills have replaced hand drills and hand braces in timber work because they are faster and easy to operate. Power drills are operated either by electricity (Electric drills) or by compressed air (pneumatic drills).
There are two types of power drills, the heavy duty type and the light duty type. Figure A below shows the heavy duty type and Figure B shows the light duty type.
Normal power drills rotate the drill bit fixed to it at very high speed and make drill holes of required size. In some drills the speed is adjustable according to the cutting material.
Twist drill bits, usually made of High Speed Steel (HSS) are used in drilling wood, steel and other soft metals. Drill bits are available from 1mm diameter to 25mm or more with 0.5mm steps. For portable power drills the maximum drill size is 10 or 12mm.
HSS drill bits are not suitable for drilling masonry. The type of drill bit used for masonry are carbide tipped bits which are used with hammer drills, which have a percussion effect in addition to rotation.
For electrical safety it is best to use power tools rated at 110 volts. Since the normal power supply is 230 volts, a step down transformer 230/110 volt should be used with power tools. For more safety battery operated power drills are now available. Figure below shows a battery operated power drill.
Power drills with variable speeds can also be used as screw drivers to drive and remove screws.
Sanders or sanding machines are power tools used to smooth finished frames and wood items. Sanders have the means to attach sand paper and to move it rapidly over the wood. These may be powered by electricity or compressed air. There are three types of sanders.
Orbital sanders – In the orbital sander the disk with the sanding pad rotates while moving in an orbital path. This ensures that the sanding material does not travel the same path twice thus ensuring that there are no swirl marks.
2. Belt sander is a machine which consists of an electrical motor that turns a pair of drums on which a seamless loop of sandpaper is mounted. Belt sanders can be either hand-held, where the sander is moved over the material, or stationary (fixed), where the material is moved to the sanding belt. Stationary belt sanders are sometimes mounted on a workbench, in which case they are called bench sanders.
The Disk Sander is fixed to a work bench and the material to be smoothed is moved over the sanding surface. Disk sanders are dangused to smooth materials such as woods and plastics. It is also used to remove small amounts of waste material. It is a dangerous machine if serous machines and goggles, hand and finger protection must be worn when using
Cleaning and storing portable power tools.
Power tools should be well maintained to give better service and long life. Maintenance of power tools include:
1. Cleaning after use – Brush or wipe off dust and cut material, lubricate moving parts, clean and check electrical contacts.
2. Cable care – Check power cable for any damages or loose connections. Promptly replace if damaged. Fold the cable back to position.Store – Store securely in its proper location with due regard to tool safety and user safety