KNRLR - a tool for making knurled bolts which are actually spiky

thingiverse

Attach this accessory to your Dremel tool for creating custom M8 knurled bolts, despite its technical name as "spiked" bolt. The creator made this due to the unsuitability of standard Ultimaker knurled bolts with his current extruder design. Modeled in 3dsmax, it requires two M3x8 screws, one M3x20 screw, and an M8 nut (non-locking) for assembly. First, attach part B to part A using M3x8 screws, then fix part B with an M3x20 screw. Remove Dremel's rubber cap and mount the hexagonal part on top of the tool. Attach a thin cutting disc before placing the bolt you want to knurl through the round hole in part A. Secure the 17-tooth gear on the bolt while ensuring its bottom layer faces toward the tip. Screw an M8 nut to secure the gear and begin cutting by holding Dremel at max speed, pushing the bolt towards the disc. Rotate the bolt for new cuts until completed. This process is quick, easy, but requires safety precautions. The resulting bolts have excellent grip properties, yet untested in real use due to ongoing extruder development.