This calibration board helps size the holes for captive metric nuts (sizes M3,M4,M5,M6).Print this calibration board to help size the holes for captive metric nuts. The easiest way to make nut holes is to do a cylinder in openscad and set the facet count ($fn) to 6. It is assumed that you are making nut holes this way.Metric nuts actually are specified as a size range, with the diameter of the nut body ranging from a specified minimum to as much as 10% larger.The scad file has the increment set at .1mm. This should size most nuts, but you can change the range or the increment in the scad file if necessary.The actual size of the hole may vary depending upon what software you are using to slice your model. For example Slic3r uses the centerline of the nozzle as the measuring point, tending to cause holes to be a bit smaller than nominal.The calibration board (as currently specified in the scad file) is laid out as: ----- RADIUS M6 5.5 5.6 5.7 5.8 5.9 M5 4.4 4.5 4.6 4.7 4.8 M4 4.0 4.1 4.2 4.3 4.4 M3 3.0 3.1 3.2 3.3 3.4