I suggest printing at 0.3mm layer height with 3 perimeters at 25% infill in either ABS, nylon, or PET for temp resistance. Extruder parts shown in images are all printed in Colorfabb XT.

This direct drive extruder conversion was made to use hardware that came with the original extruder (Greg’s hinged accessible extruder) in the 8” i3 kit while reducing weight and complexity. The only part purchased separately was an mk8 drive gear (http://reprap.me/extruder/mk8.html). I made it to fit the E3D v5 hotend but it should fit the v6 as well. I can’t speak personally to pairing it with a jhead but it mounts to the x-carriage via a groovemount plate so it should work the same. I have also included a version without the backstop (this presses against the carriage to decrease stress on the extruder when disengaging the idler). I also remixed the design of the cooling duct (https://www.youmagine.com/designs/e3d-30mm-fan-duct) for the E3D heat break and mounted it to blow outwards. This orientation prevents blowing air across the part when printing ABS, nylon, or other materials with a propensity to warp. The cooling duct for the 50mm blower can be found here: https://www.youmagine.com/designs/50mm-blower-for-makerfarm-direct-drive-extruder  

Assembly instructions:

1.      Using a 3mm drill bit or screwdriver, remove material from holes on idler.

2.      Use a 2mm or slightly larger drill bit to clean out filament guide hole in extruder.

3.      Place M4 nut into nut trap on short side of the extruder base before attaching NEMA 17 stepper motor with (4) M3x10mm socket head cap screws.

4.      Insert dowel pin through 608 bearing and press into channel on idler. It may be necessary to use a pair of pliers.

5.      Place M3 nuts into nut traps on back of idler. The fit will be tight so you may have to use a pair of plyers.

6.      Place M3 nut into nut trap on backside of extruder motor mount and attach idler to extruder body with M3x30mm.

7.      In order, place M3 washer, spring, followed by another M3 washer onto M3x50mm screw. Insert end of screw into slot on front of extruder and thread screw into M3 nut from step 5.

8.      Repeat step 7 for second M3x50mm screw.

9.      Insert end of aluminum heat break into hole on bottom of extruder and slide groovemount plate onto heat break.

10.  Install entire assembly onto x-carriage using 2 M4x15mm screws and nuts using the two holes on horizontal portion of x-carriage.