Industrial CT Scanning Combination Lock Analysis

Sometimes, the same inspection technology used in advanced manufacturing can solve a much more relatable problem: a forgotten lock combination.

At the Nel PreTech Corporation CT lab, a simple household lock turned into an interesting demonstration of how industrial CT scanning can reveal hidden internal features without disassembly.

A Summer Cleaning Mystery

With school letting out for the summer, my son was cleaning his room when he came across an old 4-digit combination lock. The problem was simple: nobody remembered the code.

Trying every possible combination manually would mean cycling through all 10,000 possible number sequences. Even at a pace of two seconds per attempt, that process could take more than six hours.

Rather than spending the afternoon testing combinations, I decided to approach the problem like an engineer.

I brought the lock into the CT lab for a non-destructive scan.

Poroma 4-digit Mechanical combination lock ($8.99 on Amazon for a 2-Pack)

Brand

Puroma

Special Feature

Weatherproof

Lock Type

Mechanical Code Lock

Item dimensions 

L x W x H

3.15 x 1.73 x 0.8 inches

Material

Alloy, Steel, Zinc

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The Puroma 4-digit combination padlock is made up of three main physical parts: the Shackle (the U-shaped bar that locks and unlocks), the Lock Body (the zinc-alloy base that protects the internal mechanism), and the Combination Dials (four scrolling wheels)

1. Main Components

• Shackle: The curved metal bar. On Puroma locks, this usually pops up or pulls out when the correct code is entered. It contains an internal pin that engages with the code dials.
• Lock Body: The outer shell that houses the brass or steel inner cylinders. It is often weather-proofed for both indoor and outdoor use.
• Combination Dials: Four rotating wheels, each numbered 0 through 9. Together, they provide 10,000 possible unique combinations.

Link to a YouTube video of someone taking apart this exact lock:

https://youtu.be/fmwLfQdwHQY?si=fa3ziHL8Zr_NmGut

Using Industrial CT Scanning to See Inside the Lock

Industrial CT scanning made it possible to inspect the complete internal assembly without cutting the lock open or damaging the mechanism.

Using X-ray projections captured from multiple angles, the scan generated a detailed volumetric dataset that revealed:

• Combination dial alignment
• Internal shackle teeth positions
• Lock body geometry
• Dial notch locations
• Mechanical engagement features

This type of non-destructive inspection is commonly used throughout manufacturing industries where internal visibility is critical.

Applications often include:

• Battery failure analysis
• Additive manufacturing inspection
• Porosity analysis
• Medical device validation
• Aerospace component inspection
• Assembly verification
• Dimensional metrology

In this case, the same technology was simply being applied to a forgotten combination lock.

The Engineering Behind the Lock Mechanism

Inside the lock are four rotating combination dials. Each dial contains an internal notch that must align precisely with a corresponding tooth on the shackle for the lock to open.

The scan showed that the lock had been left in the “0000” position, but the internal notch locations revealed the actual combination needed to align the mechanism correctly.

By analyzing each dial individually, I determined how many positions each wheel needed to rotate to align the internal notches.

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A Real-World Example of Non-Destructive Testing

While this project was done for fun, it demonstrates an important principle behind industrial CT scanning: the ability to inspect hidden internal features without damaging the part.

That capability becomes especially valuable when working with:

• High-value aerospace components
• Medical devices requiring validation
• Battery cells with internal defects
• Additive-manufactured parts with hidden porosity
• Assemblies that cannot be sectioned destructively

Traditional inspection methods often require cutting parts apart to understand what is happening internally. Industrial CT scanning eliminates that limitation by allowing engineers to evaluate complete internal geometries in 3D.

Even something as simple as a lock demonstrates how much information can exist beneath the surface of a seemingly straightforward mechanical assembly.

CT Scanning Beyond Traditional Manufacturing

One of the more interesting aspects of industrial CT technology is its versatility. Nearly any object can become an engineering investigation when viewed through CT data.

At Nel PreTech Corporation, industrial CT scanning supports industries ranging from aerospace and automotive to medical manufacturing and advanced materials research. But projects like this also help demonstrate the accessibility and visual power of the technology itself.

A forgotten lock combination may not be a production-critical failure analysis project, but the same inspection principles apply.

The ability to see what cannot otherwise be seen continues to make industrial CT scanning one of the most valuable tools available in modern engineering and metrology.

Industrial CT Scanning Services at Nel PreTech Corporation

Nel PreTech Corporation provides industrial CT scanning services for dimensional inspection, internal defect analysis, assembly verification, porosity evaluation, and non-destructive testing across a wide range of industries.

From highly engineered aerospace components to unique one-off investigations, CT technology delivers insight that conventional inspection methods often cannot provide.

To learn more about Nel PreTech’s industrial CT scanning capabilities, contact the team for a consultation or request a quote today.