This is a tool to make M8 hobbing bolts.It uses two 608 bearings to hold an 8mm bolt.The tool assumes a lathe tool holder of at least 10x10mm... I used it on my Rotwerk EDM350DR and it worked fine :)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 608 bearings. Insert the bolt through the bearings with any necessary spacers.Tighten two nuts 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. 200-400rpm seems to be working fine for M3, M4 hobbing.