parameterizable belt tensioner

This is a belt tensioner I developed to assist in tracking down vibration problems on my printer. It has [may have] a knurled knob for reproducible adjustment.

Update 03 April 2018: Modified to work with 20t toothed idler, M3 or M5 spindle. For this size idler the knurled knob around the m5 nut is too small to be useful. Instead I just use a flathead screwdriver from the sides to turn the nut. I advise using a silver nut so you can mark one face with a permanent marker and count the turns