Inside an Electric Screwdriver

Switch Block

The switch block really has two roles in this screwdriver:

  • In the center position it prevents electricity from flowing to the motor.
  • It can supply power of either polarity to the motor, so the motor can spin in either a forward or reverse direction.

An outside and inside view of the screwdriver's switch

The two metal loops at the bottom of the switch are on either side of a contact that leads to the motor. With the switch in its neutral position, nothing touches the contact. But when you move the switch to one side or the other, one loop touches the contact, completing the circuit.

The two loops at the bottom of the switch slide to touch a metal contact.
©2007 HowStuffWorks

The wires deliver electricity from the batteries. The batteries and the contact for recharging them are inside the screwdriver's handle.

The batteries and handle
©2007 HowStuffWorks

Gears carry the motion from the motor to the screwdriver bit. On the next page, we'll take a look at how the gears fit together.­