Prusa I3 Rework Drop In Replacement/Upgrade Herringbone Gear Set with Solidworks 2014 source

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I was never clear on why herringbone gears needed an entire extruder upgrade to work properly, so I set out to create some replacements that wouldn't require any adjustments to your e-steps when swapping them in. After making these gears, I can confidently say there is essentially no noticeable backlash at all (and when I say "no backlash," I might even be overstating it slightly), as compared to spur gears which always have a noticeable amount of backlash that's easily detectable. One thing to note about herringbone gears is that they don't mesh together too smoothly by nature, so ensuring the outer layer of both gears are perfectly flush with each other is crucial. 12/21/2014 - Added less material big gear in .stl for those without access to SW 2014+ 11/6/14 - I removed the old small gear because I realized the hole for the 3mm grub screw was off-center, so I corrected that and made the part a bit stronger where it goes. Also, I enlarged the stepper shaft slightly to make fitting easier. Source and STL have been uploaded. Instructions: 40% - 100% infill with 200 micron layer height. First layer at 280 microns. Six vertical and top/bottom horizontal shells are recommended.