Normally a calibration probe for Z axis is enough for 3D printer, be it a magnetic sensor, a hall probe like BL touch or a simple switch that clicks at touch.

Not true when you work in 5 axis, your bed tilts, and needs calibration mapping before every print individually. That is another beast all itself.

Using a CNC calibration probe is not good, for CNC working beds are stiff by nature, while 3 D printers have beds on springs, so a more sensitive tools is required.

So after a few months of design, print, test, cursing and reiterate the design, print, testing, cursing and back to drawings for i don't remember how many times, it finally works.

I never thought that inventing such a small and delicate device would drain my psyche as it did.

Unlike the CNC probing tools that have 3 points of breaking the contact, I needed 5, and in a small tool, and very sensitive to touch, and simple, and cheap, and easy to make.

And here it is.

3 elements to print, the body, the probing stylus holder and the top element.

You will need to buy adequate metal threaded inserts (M3, M4, M2.5) some 20 and 30 mm long bolts (M3 and M2, and M2.5) obviously the corresponding nuts, large washers, and the stylus of your choice.

Additionally if you have not printed a calibration holder, now is the time to do it. This assembly is intended to work both on the Flip manually tool swap system and on the automated flip tool swap system, in case you have not installed one, you might want to do that now.

Insert all threaded inserts in their holes accordingly, the one for the stylus in the stylus porter, and the two ones for the bolts where they belong to match the top piece (if you printed all in nylon or better, no ned for inserts for the top piece, threading the nylon with the bolts once is good enough)

Place the stylus in the porter tight, insert the assembly in the cleansed holder (is finicky to clean it) and once is in position (you might need to slightly enlarge the passing hole, make sure you do so but not exaggeratedly) place one by one the 4 microswitches and bolt them in with their nuts over large washers.  Make sure all 4 tips of the microswitches touch the probe but none too hard so that the probe can travel up and down feely while caressing the tips of the switches.

When done place the top piece firmly and bolt it, than place on it the fifth switch and bolt it so that it touches the probe head without preventing it from moving sidewise at will.

The probe is ready to be connected, you will either need to connect the 5 pairs of the wire in the Arduino or you will make a small PCB to hang on the probing tool somewhere with a microchip converting analogue to digital signal and take only 2 wires to the Arduino board.

When ready bolt the Calibration Probing Tool to the Flip Carrier slide while the slide is fitted to the Calibration Holder, make sure the tip of the stylus falls perfectly in the centre without clicking on any of the switches before you mark for the holes to bolt it to the holder.

Same method is to be applied to all your printing heads to make sure that swapping any tool gives you zero placement errors and all tips are going to be in the same exact place no matter what you swap.