Simplified underbed piezo sensor mount

This is a simplification of my combined bed mounting and piezo nozzle contact sensor https://www.thingiverse.com/thing:1399512 and is shown in the sectional drawing. A 27mm piezo disc with a hole drilled in it is fitted between the bed adjusting nut and carriage. The piezo can be mounted directly on a flat surface on the carriage under a pad - this gives very low compliance; or it can be mounted on the ring abut without the pad, this method giving better sensitivity but more compliance. Many details on this and others on http://forums.reprap.org/read.php?1,635075,page=1
Two nuts are provided for 3mm or 4mm bed jacks. Glue or otherwise fix a nut, preferably Nylon or Nylock in the recess. Amplifier/conditioner DIY or from https://www.precisionpiezo.co.uk/shop
Take care drilling the hole in the piezo element, use a sharp drill and hold the piezo to a flat surface with strong tape. Drill 5mm hole for a 3mm jack or 6mm for a 4mm jack.. The ceramic powder may be injurious to the health, cl