Parts

The same PCB is used for both the upper and lower half, and uses 4, 1/4x1/8 axialy polarized magnets, an SPDT snap action switch, M2 & M3 mounting screws, and some other random bits and bobs you probably have laying about.

The parts list specifies an Omron snap action switch: the most common subminiature size of the Omron D2F switch series, but almost any subminature switch will work. The circuit only uses the Normally Closed (NC) half of the switch as a momentary pushbutton. Testing has shown that other switches of the same package size will work and their repetability is good enough for use as a Z probe. Reliability testing has shown name brand switches to have a standard of deviation of the trigger point on the order of 0.002mm, and no-name aliExpress and ebay generics to be be 0.004mm- a full order of magnitude better than BLTouch and inductive probes and similar variants.

The operating temperature range of most mainstream switches of this class are 80°C, so theoretically the probe should function in a heated chamber of 60°C.