Exploring the Internals of an Electric Screwdriver

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An electric screwdriver. View more power tool images.
©2007 HowStuffWorks

Electric screwdrivers are fascinating as they amalgamate batteries, motors, gears, and switches into a single, compact, and powerful package. Let’s dismantle one and see what lies inside! Here’s the screwdriver we will be examining:

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After removing the cover, you’ll find all the essential components of the screwdriver arranged in a line from one end to the other. These include:

  • A rechargeable battery
  • A switch
  • An electric motor
  • A dual planetary gear system (how cool!)
  • A simple locking mechanism for the chuck
  • The chuck itself, which holds the screwdriver

The ridges inside the case and two long pins hold all these parts together.


©2007 HowStuffWorks

The components inside are pretty basic. We’ll examine the switch and how it transmits electricity to the motor in the next section.

Switch Block

The switch block serves two roles in this screwdriver:

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

An exterior and interior 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, the contact remains untouched. However, 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 transmit motion from the motor to the screwdriver bit. On the next page, we’ll delve into how the gears interlock.­

Electric Motor


The electric motor
©2007 HowStuffWorks

The electric motor is a standard DC electric motor. See How Electric Motors Work to see the parts inside an actual electric motor.

At the end of the motor is a small 6-tooth gear. This gear fits into the center of the planetary gear system, as shown here:


The central gear of the three smaller gears is linked to the motor.

The electric screwdriver’s gear system is its core component. An electric motor alone cannot produce much power. You can easily halt the rotation of a small motor by gripping its axle. However, if the motor is geared down significantly, it can easily drive a screw into a piece of wood with great force. This screwdriver employs a dual planetary gear system with a 56:1 reduction ratio. This means that the motor rotates 56 times to turn the chuck once. Thus, the chuck moves slowly in relation to the motor, but has a high amount of torque (it requires 56 times more force to stop the motor from spinning due to the gear ratio).


©2007 HowStuffWorks

The central gear must turn about three times to rotate its three neighboring gears once. These gears must turn about two and a half times to move around the outer ring once, totaling around 7.5 turns. The outer ring remains stationary, while other gears move inside it.

The gear set has two identical layers, one on top and one on the bottom (the bottom layer is concealed behind the top and cannot be seen in the photographs). The gear system’s top layer attaches to a small table with a second 6-tooth gear underneath. This gear rotates once for every 7.5 motor rotations, due to the top layer’s movement. The bottom 6-tooth gear requires 7.5 turns to move the bottom gears around the ring once, resulting in a gear ratio of about 56.25:1. The bottom gears are connected to a piece of metal that rotates the chuck once for every 56 motor rotations.

For more information on how electric motors work, read How Motors Work. For more information on how gears work, please read How Gears Work. To learn more about power tools and related topics, follow the links on the next page.

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FAQ

1. What is an electric screwdriver?

An electric screwdriver is a power tool that is used to tighten or loosen screws. It is powered by electricity and has a motor that rotates the screwdriver bit.

2. How does an electric screwdriver work?

When you press the trigger of an electric screwdriver, it sends an electrical signal to the motor. The motor then converts this electrical energy into mechanical energy, which rotates the screwdriver bit. The rotation of the bit helps to tighten or loosen the screw.

3. What are the advantages of using an electric screwdriver?

An electric screwdriver is faster and more efficient than a manual screwdriver. It can also be used for longer periods of time without causing fatigue. Additionally, electric screwdrivers come with a variety of features such as adjustable torque settings, which make it easier to work with different types of screws.

4. What types of electric screwdrivers are available?

There are several types of electric screwdrivers available, including corded and cordless models. Corded electric screwdrivers are more powerful and are ideal for heavy-duty jobs, while cordless models are more portable and convenient to use.

5. Can an electric screwdriver be used for other tasks besides tightening or loosening screws?

Yes, an electric screwdriver can be used for a variety of tasks such as drilling holes, sanding, and polishing. It all depends on the type of bit that is attached to the screwdriver.

6. How do you maintain an electric screwdriver?

To maintain an electric screwdriver, you should keep it clean and free from dust and debris. You should also periodically check the screwdriver’s bits and replace them if they become worn or damaged.

7. Are there any safety precautions that should be taken when using an electric screwdriver?

Yes, it is important to always wear protective gear such as safety glasses when using an electric screwdriver. You should also make sure to read the manufacturer’s instructions and follow all safety precautions.

8. What should you consider when purchasing an electric screwdriver?

When purchasing an electric screwdriver, you should consider factors such as the power of the motor, the type of bits that can be used, and the overall design and ergonomics of the screwdriver. You should also consider your specific needs and the types of projects that you will be working on.

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