Actuation Force vs. Bottom-Out Force: What are the differences?

Overview

Different switches have different actuation and bottom out forces, but what's the difference and does it make it difference in the switches you should use? Actuation force and bottom out force are measurements of how hard or how much weight you need to use to press down a key. It is usually measured in "gf" (g-force). Generally, the actuation force and the bottom out force is related to the weight of the spring used in each switch.

Actuation Force

The actuation force is the minimum force required to press down and actuate the switch or register the keystroke.

For linear switches, the actuation force is usually around halfway through the full travel distance of the switch. A linear switch is straightforward since there is no tactile bump to suddenly change the feel.

For tactile switches, the actuation force is usually around when you feel haptic feedback from the tactile bump along the keypress. The actuation of a tactile switch usually happens right after the sudden increase in force cause by the tactile bump, therefore the actuation occurs right after the bump when the force is less than before the bump.

Bottom Out Force

The bottom out force is the maximum force required to press down and fully compress the switch and travel its full travel distance.

Depending on the design, bottoming out can occur when either the stem pole (long pole stem or switches with shorter travel distances) or the stem rails (full travel switches) make contact with the bottom housing of the switch.

Like the actuation force, linear switches are straightforward since it is just one motion from beginning of the keypress to the end while tactile switches

What is Operating Force?

You might have heard the term "operating force" used interchangeably to describe the weight of a switch, but what exactly is it referring to? Operating force is most closely interchangeable with the actuation force.

Why Do These Matter and How Do These Affect Your Choice of Switch?

Depending on if you are a light typist or a heavy typist, either the actuation force or the bottom out force would be good to know before purchasing a switch. If you are a light typer then the actuation force would be a more relevant piece of data since you only press until the key registers. If you are a heavy typer then the bottom out force would be the relevant information because you would be bottoming out during typing.

Other Factors that May Affect the Typing Feel

Spring Length
- There will be a less noticeable difference in the downstroke for different spring lengths, but there will be a more noticeable difference in the upstroke.
- A longer spring length will feel more responsive on key up since the switch stem will bounce back up with more force than a shorter spring.
Lubrication
- Lubricating switches can make switches feel smoother to actuate by reducing the scratchiness caused by rubbing plastic on plastic.
- Depending on the amount of lubrication used, sometimes adding a large amount could cause the switch to feel "heavier" or more sluggish.
Switch Travel Distance
- Switches with shorter travel distances can feel more abrupt since the keypress will stop short, or they can feel more responsive depending on your typing style.

Share your thoughts in the comments and let us know if you have any questions!

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