This is a simple printable tool for hobbing bolts.
Designed to use (2) R6zz ball bearings from vxb.com to hob a 3/8in bolt
Can also be used to hob 8mm bolts with 608zz bearings with some minor modification, though a small amount of tape is required to make the bearings fit snugly.
The tool assumes 1/2in from tool bottom to lathe center on a 8x16 lathe.
Print the hobbing tool at very high infill with support enabled (there is only a small amount of support required)
Remove support, press in the R6zz bearings. Insert the bolt through the bearings with any necessary spacers.
Tighten a nut on the bottom of the bolt. It should be snug, but still allow the bolt to rotate easily.
Put in lathe tool holder and begin hobbing.