This is a small adapter plate that allows you to attach a bowden tube to a (Greg's Accessible) Wade's extruder. I hacked it together based off of Mark's very nice bowden adapter and mount. (I just didn't need the M8 rod mount part... I use it with my own mounting block found here:http://www.thingiverse.com/thing:73763 )
I have included STL files for using an M4 nut, or a commercial Push To Connect tube adapter. The SCAD file can make either.
Print the part. Drill out the M4 holes to the proper size (11/64 drill works). I also recommend drilling a 3-4mm deep 4-5mm hole (I used drills from a 1/8th up to an 11/64th one at a time to make sure I didn't go to deep) into your extruder body so that the 4mm OD tube can be threaded past the end of the nut and top of the adapter plate (and fit into the hole).
Screw an M4 nut onto your (4mm OD) Bowden Tube. Slip the tube into the slot, push the nut into the cutout. Stick a piece of filament through your Wade's extrder, slip it into the bowden tube, then using the filament as an aligning tool, bolt the adapter to the bottom of your Wade's Extruder. (Note, I also have a base mounting plate that holds the stepper at the correct angle to use this part on a Rostock-mini printer, see http://www.thingiverse.com/thing:73763 )
Note: unless your Push To Connect adapter is a good one (i.e. that will actually release the tube without breaking) you may as well just use an M4 not screwed onto the tube. This part is simpler, but you'll have to drill out and tap the hole in the center to match your PTC adapter.