Tinker toys for big kids!
This is a small printable cube that is used to construct frames and build objects using 5/16" all thread rod. 5/16" is the SAE size that will conveniently hold a 608 skate bearing.
The uploaded stl has holes through all 3 axes with one captive nut embedded in the sidewall. This holds your rod/nut in place as you tighten the other nut on. If you'd prefer captive nuts on both sides of each hole, then simply uncomment the noted line in the openScad file.
The location of the three axis holes and depth of captive nuts have been tuned to make roller bearings for 1/2" black iron pipe using standard 608 skate bearings. Bring your weird machines to life with dirt cheap all thread rod!
The typical usage is to press-fit a captive nut into all three axes and thread in rods where you want them. Alternately, some construction is easier if you put the nut on the all thread first and then insert the whole assembly into the captive nut recess. On the opposite hole, a washer is recommended before the second nut to distribute the load.
It is of course possible to use washers on both sides and avoid the captive nut recess entirely, but one captive nut makes pre-adjustment and tightening much easier. Or, just recompile with no captive nuts for a generic building block.
The Z axis from top to bottom (perpendicular to the print plane) should be the strongest and can be used to bear the greatest load. However, when arranged in a cube or frame and tightened with nuts on each side the entire assembly can be quite strong in all dimensions.
For easiest assembly, you may want to drill each of the axes out with a 5/16" drill press. This will make the rods slide smoothly through the holes.
The scad file is not quite parametric, but is variable-based so regenerating a different sized cube for metric or other size allthread should be rather simple.