The printrbot team working on the hot end decided to take the Microsoft approach, and not make itself backward compatible with existing hot ends... This frustrated the heck out of me, so i designed an adapter so any hot end will fit.
Really printrbot? Come on.
Print this, and install in between the existing mount.
See the skp file for a diagram how it all fits together...
Please feel free to make this design better.
V2.0: Added slot for 6-32 nut for top mount. Use 1" 6-32 screw.