Carriage bolt thumb head (imperial)

thingiverse

This is a screw cap designed to fit a carriage bolt. Many makers have created knobs that attach to hex screws or bolts, but finding large hex bolts can be challenging. This solution is intended for situations where you need to visit the big box store and purchase a carriage bolt. The sizes are based on US carriage bolts: "#10", "1/4", "5/16", "3/8", "7/16", "1/2", "5/8", "3/4", "7/8", "1". I included both short (knurl=12) and tall (knurl=50) caps for sizes #10 through 3/4. The naming convention for a file like 5.8-h18k12f1.05.stl indicates that it is designed for a 5/8" bolt, with a cap height of 18mm, 12 knurls, and an expansion factor of 1.05 to account for tolerances and plastic shrinkage. The size has been engraved on the underside (hidden from view). Customizers can adjust: size, knurls, height. If you download the file and run it through OpenSCAD, there are functions available for rendering a carriage bolt, a carriage bolt cutout. Features like diameter and font can be easily modified.