Hot End/Nozzle  

When properly assembled, you can't tighten the nozzle flush against the block

Posted by: @rufus

So in the manual p73 pict42 it states that the nozzle should have a gap between the heater block and the hex of the nozzle. What is that gap and why in the world is there NO shims or stops on the tube housing that threads into the heater block?? 

Most of the instructions aren't clear on this, but if you've assembled the heatbreak and heater block correctly, it should be impossible to tighten a proper v6 nozzle flush against the block. The heatbreak itself as screwed into the block is the stop. It's easiest to verify everything with the hotend removed from the extruder housing.

Also can someone tell me if the filament is supposed to stop just before leaving the tube housing and entering the nozzle? In other words the filament is not able to push all the way to the nozzle but is stopped at the end of the tube, melted and then pushed into the nozzle as gel??

The filament should be melting as soon as it goes past the "transition zone" through the narrow neck and into the heater block. You'll see this when you do a cold pull as a good pull will show the inside of the heatbreak and nozzle.

Great explanation

Thanks for the reply. Very helpful just to bad Prusa is not as straight forward