Lots of keys fit in the hole. Why does only one key let the lock turn?

10 mm12345housingshear linespringdriver pinplug (turns)tumbler pinboltarm
key in
0.0 of 24.0 mm
cut depths
no key
pin gap vs shear line
−1.8 · −2.8 · −1.0 · −2.4 · −1.4 mm
spring squeeze
3.3 · 2.3 · 4.1 · 2.7 · 3.7 mm
spring push (F = kx)
0.33 · 0.23 · 0.41 · 0.27 · 0.37 N
plug
0°
bolt
moved 0.0 mm

Press the steps in order, or press Auto. It runs in real time. Watch the pin gap numbers: 0.0 means that gap sits right on the shear line.

How a pin lock works: Lemelson-MIT Program (Linus Yale profile) and European Patent Office, EP 1 961 896 A2 (Background: plug, housing, driver and tumbler pins, springs, shear line, bolt). Spring push from Hooke's law, F = kx, in OpenStax College Physics 2e, 16.1. Every size, cut depth, spring stiffness (0.1 N/mm), key speed and turning speed, and the arm and plate that move the bolt are example values. Drawn to scale in millimeters with the Anatomy kit (MIT license).