Work in Progress... This is a modification (more like a hack) of DuexVis' Techzone Huxley LM6UU X-Carriage. And version 2 and up takes the slim bearing holder from simonkuehling http://www.thingiverse.com/thing:16208. Thank you both for sharing and including all of the required OpenSCAD files. DeuxVis did the hard work for me by designing the object and figuring out the placement of the bearing holders. I just changed a few dimensions to suit my needs. And thanks to simonkuehling for the slim holders.
I needed a larger hole so I could drop my hot end down through the hole instead of pushing it up into the snug hole. I'm using a j-head nozzle Mark IVb from Hotends.com that is held by the original TechZone clamp. No other support is needed. So, I don't even need the 2 holes used to hold the peek block.
update: I printed and installed this on my Huxley. I posted more pictures.
Also printed PLA bushings (http://www.thingiverse.com/thing:16464). Soon, I'll update to these modified to 6mm (http://www.thingiverse.com/thing:16813). I'm still shopping for reasonably priced 1/4" bearings. And I'm hesitating on switching my printer to 6 mm smooth rods and bearings.
I am still working on the design of the .scad files. Let me know if you have any suggestions.
To make mods to the .scad files, follow the instructions in DeuxVis' original version. And add the 2 scad files from here to DeuxVis' files. I just made mods to a few of the sizes in the x-carriage.scad. And I modified the slim bearing holder from simonkuehling to fit 6 mm bearings. That modified file is also included here.
Any where I made changes, the original code is commented out and my changes follow.
Please let me know if there are ways I can improve how I made the changes. I'm new to OpenSCAD and 3D printing as well. I'll make changes as I learn and improve.
I also included pictures of my original TechZone Huxley carriage and hotend holder. I have the Mark IVb j-head attached. I can remove the entire holder and hot end together by pulling them up through the larger hole.
Update: As others have noted with the 8mm bearing holder, the original holders were not strong enough. So, I followed the advice of the others and increased the wall thickness of my modified 6mm holders. I'll upload the updated holder file and a new stl soon. I just printed the thicker one and the walls seem strong enough now. My friend printed the green one in the [I made one] picture with the thinner walls. After playing with the print for a while, all of the tabs broke off. I think this problem is solved with the thicker design.