Electric drills are portable drilling machines. This device is powered by an electric motor carried within its casing. Apart from the motor the other main components include the chuck which encompasses the drill and a basic gear train that controls the speed of the rotating drill.
Most domestic electric drills take on the appearance of a pistol. This design is used to give the operator easier handling. The power cord is attached to the base of the grip and the on/off switch is incorporated into the trigger. In many cases an interlock is provided so that the trigger does not have to be pressed down continuously.
The motor is shielded by its casing and is usually of a universal or series type. The advantage of this sort, is that it is suitable for both DC and AC currents. It also has the capability to produce a high torque at low speeds. If the drill is pushed harder to the surface which it is boring the speed will decrease and the torque will increase. The gear train component can reduce the speed to around 2500 revolutions per minute.
In the 1980's the cordless drill became very popular, this drill is exactly the same in operation as standard electric drills but the power for the drill is sourced from a clip-on battery pack. The pack is removed periodically and recharged as required.
