Hi, time to show what i came up with after some strange experiments ;p
so i prefer to actually put some PTFE for "lubrication", but it's a mate of one element and you have true all metal (tested by a friend).
It's quite reprap and rep-strap friendly - just a simple aluminum interface, piece of plate
Most important thing is, that single pipe goes all the way from cold to hot. No place for block or to deform PTFE if present Additional aluminum is used to suck up the heat clean and make transition length just 10mm long + 10mm in hot zone but with some insulation and then just model the nozzle how you wish, fast, precise, long short and - the thing I'm most proud of is this: [
www.youtube.com]
check the project here [
www.reprap.org]