Use the following standard parts for build:

2x hexscrew M2x12mm

1x hex bolt M10x80mm Stainless Steel

1x brass tube Inner Diameter 10mm Outer Diameter 12mm, 20mm Length

1x microswitch

How to:

• Cut the Hex bolt at 26mm under the Head
• Use a grinder and a Drill. 
• Clamp the Screw into the drill and rotate it and use the grinder to give the shape. 
• The head should be approx H4mm, D16mm
• Press the brass tube into the printed part
• screw the microswitch to the printed part, use the nut to close the hole

READY.

The bolt should move up and down easily. There should be 0,15mm tolerance between the bolt and the brass tube. The spring force of the microswitch is enough to lift the bolt. After a few runs I can confirm an accuracy of 0.02mm.