Ultimaker 2+ DIY Hobbed Bolt

I wasn’t satisfied with the original hobbed bolt of the ultimaker 2+. When you look at it, it looks more like a file. And so it handles the filament –  I got a lot of shredded filament.

I used a M10 screw and built something like a lathe with my cordless drill. I wouldn’t recommend this, as the bearing isn’t designed for axial load. I cut off the head using a iron saw and used a file to remove the thread and get a diameter of 8mm on the outer parts. On the part that is like a file on the original i left all the thread. With this assembly you get a perfectly round shape, however its very likely that it won’t be cylindrical but conical. I used a caliper to avoid this.

I used a rotary tool to flatten the part, that connects to the extruder gear. Here it is very important to get the right size, otherwise the torque will break the plastic gear.

At last I used the same rotary tool, to cut 16 axial notches into the thread. I didn’t use any kind of angular helper tool. Here you see the result:

Even though the DIY bolt looks bigger, it fits sufficiently into the extruder and work well after 1kg of filament.