Exploring the Inner Workings of a Combination Lock

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Combination locks are a common sight, but have you ever wondered what’s inside them? In this article, we will take a peek into the secrets of a combination lock. Let’s take a look at the lock itself:

Opening a lock is not always an easy task, but that’s what keeps the lock secure. Once you do manage to open the lock, you’ll find an array of parts that look like this:

A typical combination lock has three cams. One of them is a metal cam that’s directly attached to the turning face of the lock, while the other two are made of plastic. Two plastic spacers fit between the cams:

These spacers are placed on a shaft at the back of the lock and held together by a spring that provides friction between the cams, keeping them in place when the lock is assembled.

Each cam has a tooth on both sides, and these teeth engage as the cams rotate:

The purpose of these cams is to control a latch that engages the lock’s hasp. The cams have indentations in them, and when these align properly, the latch fits into the indentations and releases the hasp:

If the indentations don’t align properly, the latch engages the hasp like this:

If you’ve ever used a combination lock before, you’ll be familiar with the process: “Turn the dial clockwise two full rotations to the first number of the combination. Then turn it counter-clockwise past the first number to the second number. Then turn the dial clockwise to the third number and the lock will open.” This is why this process is necessary. When you turn the dial 2 full revolutions, the teeth of all three cams engage, so they all turn together. When you turn the dial counter-clockwise past the first number, the first cam’s tooth engages the second cam, so the two cams move together while the third cam stays in place due to the friction provided by the spring. When you turn the dial clockwise again, only the top cam rotates. Once all three indentations are aligned properly, the lock opens.

You could theoretically stack up to 4 (or 10) cams, but it would make for a tedious process of opening the lock. Nevertheless, it would certainly be more secure!


1. How does a combination lock work?

A combination lock works by using a series of rotating discs or cams that have notches cut into them. When the correct combination is entered, the notches will align and allow the lock to be opened. The combination is typically a sequence of numbers, which are entered by rotating the discs or cams to the correct position.

2. What is the difference between a combination lock and a key lock?

The main difference between a combination lock and a key lock is the way in which they are opened. A key lock requires a physical key to be inserted and turned, while a combination lock requires the correct sequence of numbers to be entered. Combination locks are often used in situations where keys can be lost or stolen, or where multiple people need access without the need for individual keys.

3. Can combination locks be easily picked?

While it is possible to pick some combination locks, it is generally more difficult than picking a traditional key lock. Combination locks can be made more secure by using more discs or cams, and by using a longer combination sequence. Some combination locks also include additional security features, such as a shroud that covers the lock mechanism and makes it harder to access.

4. How do you reset a combination lock?

The process for resetting a combination lock will vary depending on the specific lock model. In general, the lock will need to be opened using the current combination, and then a reset button or lever will need to be activated. The new combination can then be entered and the lock closed. It is important to follow the manufacturer’s instructions when resetting a combination lock, as incorrect procedures can damage the lock or render it unusable.

5. What are some common problems with combination locks?

Some common problems with combination locks include forgetting the combination, the lock becoming stuck or jammed, and the lock mechanism becoming worn or damaged over time. These problems can often be resolved by carefully following the manufacturer’s instructions for resetting or repairing the lock, or by consulting a professional locksmith.

6. Can combination locks be used outdoors?

Many combination locks are designed for outdoor use, and are made from materials that are resistant to weather and corrosion. However, it is important to choose a lock that is specifically rated for outdoor use, as some models may not hold up well in harsh weather conditions or prolonged exposure to moisture.

7. Are combination locks more secure than key locks?

Combination locks can be just as secure as key locks, but it depends on the specific model and how it is used. A high-quality combination lock with a long combination sequence and additional security features can be very difficult to pick or bypass. However, it is important to choose a lock that is appropriate for the intended use, and to follow best practices for securing the lock and the items it is protecting.

8. How long does a combination lock typically last?

The lifespan of a combination lock will depend on a variety of factors, including the quality of the lock, how often it is used, and the conditions in which it is used. With proper care and maintenance, a high-quality combination lock can last for many years. However, if the lock becomes damaged or worn, or if the combination is forgotten or lost, it may need to be replaced.

9. Can combination locks be opened without the combination?

It is possible to open some combination locks without the correct combination, but it generally requires specialized tools and techniques, and can be difficult or time-consuming. However, if the lock mechanism becomes damaged or worn, it may be possible to bypass the combination and open the lock with relative ease. In general, it is best to keep the combination in a safe and secure location, and to be cautious of anyone who may be attempting to gain unauthorized access to the lock.

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