Summary

A telescopic adjustable mount for a Z axis endstop microswitch

Instructions

Print and assemble. Turn the screw to adjust.
M4 bolt 50mm + M4 nut + 3xM4 washers
M3 bolt 20mm + M3 nut + M3 washer
2xM2.5 bolts 20mm + 2xM2.5 nuts + 2xM2.5 washers (though can use M3 for these)
Short spring that fits M4 bolt

The print is in two parts, the clamp and the switch mount. Print in ABS.
Thread the M4 bolt as follows:
M4 washer, clamp, M4 washer, spring, M4 washer, switch mount, M4 nut
Now as you tighten and loosen the bolt the height should change.
Mount under the X-axis gantry as shown

I usually use a hall-effect switch but recently been having reliability issues with it, and wanted a way of getting a similar fine-tuning effect.

Use z-switchr.stl if you want to put the bolt thru from the top instead of the bottom - depends on your X-end clearance

Z endstop telescopic adjustable mount