I have got two 1.75mm Mk Vb jheads from hotends.com. I have not run a 3mm version so cannot compare the two sizes.
The 1.75mm size has a PTFE tube inside and I have replaced this with my own after it was damaged.
I used a 1/4" PTFE rod cut to length and I drilled a 2mm hole down the middle, the Wiki says 1/8" I think. After screwing in the brass hot end (be careful or the peek will split, just do it hand tight) the 5/16" hollow lock set screw is tightened down on the tube.
There is a short PTFE tube that pushes into the inside of the hollow lock set screw. It is 4mm od/2mm id x 7mm long, same tubing I use for my Bowden tube.
Further thought .................. my brass nozzle is drilled out to accept 1.75mm filament, not sure what diameter the 3mm version is drilled out but I don't think it will be suitable.
Edited 4 time(s). Last edit at 01/10/2015 06:59AM by dave3d.