Ultimaker Internal Axle/Bearing Cap

Based on the design by @jwags55 http://www.thingiverse.com/thing:99113 the key difference here is that the hex nut has been inset an extra 1mm. This allows two things, 1) greater hold on the nut and 2) allows it to be used in combination with my replacement outer end cap design using the same standard bolts (my external end cap is 1mm thicker than the standard wooden ones that come with the ultimaker).

Unfortunately I don't have the right CAD software to correctly modify .STEP files from the