Frankie Flood needed some custom-sized wingnuts that are commercially unavailable, so he went ahead and 3D printed his own part and then sand cast it. This process, and all of the steps he used, has been extensively photographed and shared on his blog. If you desperately need to replace hard to find parts, or are just interested in sand casting with 3D printed parts, you will no doubt find Flood's own experiments with sand casting a highly educational experience! Read more at 3DPrint.com: http://3dprint.com/120875/sand-cast-wingnuts/