Improved Knob for X and Y Tensioners

This is a modified version of the knob originally designed by Simhopp
(http://www.thingiverse.com/thing:1428253) and referenced Ratm3at's design of the hot bed knobs (http://www.thingiverse.com/thing:1708803)

I have added the ability to embed your M4 nut into the housing of the knob while printing for a cleaner over all look.

Using your slicer or printer, pause the print at 4.0mm high or layer 20 (when printing with 0.2mm layer height) pop in your nut and allow for the print to resume.