What is a Mechanical Switch?

Close your eyes and imagine the perfect keystroke. Not the mushy, uncertain squi sh of a rubber dome. Not the vague, inconsistent feedback of a cheap membrane. Imagine crisp precision—the exact moment a key registers, consistent across every press, hour after hour, year after year. That's the promise of a mechanical switch, and it's the beating heart of every custom keyboard.

A mechanical switch is a small marvel of engineering—a self-contained, precision mechanism beneath each keycap. Unlike the rubber dome sheets hiding under most office keyboards, each mechanical switch is an independent unit with its own housing, stem, spring, and metal contacts. It's a tiny engine with one beautifully focused purpose: transforming your keypress into electrical signal with exact, repeatable feedback.

Mechanical Switch Anatomy

The Magic Happens in Milliseconds

When you press a key, here's what unfolds in a fraction of a second:

  1. The Stem Descends: Your finger pushes down the switch stem (the part that connects to your keycap), which travels smoothly through precisely engineered housing guides.

  2. The Spring Compresses: Inside the switch, a calibrated steel spring compresses, providing resistance. This spring weight—measured in grams (like 45g, 62g, or 67g)—determines how "heavy" or "light" the switch feels to press.

  3. Contact! At a precise point (usually around 2mm down in a 4mm travel), two metal contact leaves inside the switch touch, completing an electrical circuit. This is the "actuation point"—the moment your keypress registers to the computer.

  4. The Return: Release your finger, and the spring instantly pushes everything back to the starting position, ready for the next press.

This elegant dance happens consistently across 50 to 100 million keypresses—that's potentially decades of daily typing—without degradation in feel or performance.

Why "Mechanical"? Understanding the Revolution

The term "mechanical" distinguishes these switches from their vastly inferior "membrane" or "rubber dome" predecessors. The difference isn't just technical jargon—it's transformational to anyone who types regularly.

Rubber Dome Keyboards: The Status Quo

In standard office keyboards, a single sheet of rubber domes sits beneath all the keys. Press a key, and you're collapsing a squishy rubber dome that pushes two layers of plastic membrane together. It's cheap to manufacture (which is why it's everywhere), but the experience is compromised:

Mechanical Keyboards: Precision by Design

Each key on a mechanical board has its own complete switch mechanism. This fundamental difference creates cascading benefits:

The Custom Keyboard Revolution

This modularity unlocked the entire custom keyboard hobby. When Cherry's MX switch patents expired in the 2010s, manufacturers worldwide began innovating, creating hundreds of switch variants. Today, you can choose switches with:

The Anatomy of Excellence: Inside a Switch

Understanding what makes switches different requires looking at their components. While hundreds of switches exist today, they all share fundamental anatomy:

1. Top Housing

The upper portion of the switch casing. It guides the stem's movement and protects internal components. Material matters:

Manufacturing tolerances here determine "stem wobble"—how much the stem can wiggle side-to-side. Premium switches minimize this for clean, precise keystrokes.

2. Stem

The star of the show—this is what your keycap mounts to and what you physically push. The stem's shape defines the switch's fundamental character:

Most modern switches use MX-style stems with a + (plus) shaped cross mount, the de facto standard established by Cherry in the 1980s. Made typically from POM (Polyoxymethylene), chosen for its low-friction, self-lubricating properties.

3. Spring

The steel coil that provides resistance and return force. Springs come in various weights and designs:

Spring swapping is among the most popular switch modifications—it can completely transform a switch's character.

4. Bottom Housing

Houses the metal contact leaves and spring, with pins that connect to your PCB:

The bottom housing material (often nylon) significantly impacts sound profile—it's what your stem impacts when you "bottom out."

5. Metal Contact Leaves

Hidden inside the bottom housing, these copper alloy leaves are what actually register your keypress. When the stem descends, it pushes one leaf into contact with another, completing the circuit. The quality and design of these contacts directly affect the switch's reliability and lifespan.

Why Your Switch Choice Matters More Than You Think

Switches aren't just about "clicky or not clicky." They fundamentally shape your entire typing experience:

The beauty is you don't have to choose one switch forever. Hot-swap PCBs let you experiment. Switch testers let you try before committing. The perfect switch for you exists—you just need to find it.

Ready to Explore the Varieties?

Now that you understand what a switch is and how it works, it's time to discover the fascinating world of switch types. Head to The Three Switch Types to explore linear, tactile, and clicky switches and find your perfect match.

Curious about the more technical details? Check out Switch Characteristics to dive deep into actuation force, travel distance, and the specifications that separate good switches from great ones.

External Resources