filament and nozzle dia

I was just thinking of how to build my future 3D printer. just had a few questions I thought i'd ask. the rest of the forum is too messy to sift information out so I thought i'd just throw it out here:

1) is there any sense to use a 0.5mm nozzle with 1.75mm filament? or will there be problems in cases where the filament cannot feed fast enough to make the volume etc?

2) if answer to (1) is yes, will I need specially made nozzles? and where can I get them from?

the reason i'm asking is this: i'm thinking of building a 3D printer which is capable of printing high resolution small items, and big, strong parts if I need. At first I was thinking about a dual extruder, but for now i've decided to choose to be a bit less ambitious first. The only thing is that if possible I want to stock only one type of filament if possible (to maximise economies of scale - a bit headache to have two different sets of filament, and in different colours too) so i'm thinking of stocking both a 0.5mm and a 0.3mm (or smaller if possible) nozzle, which I will switch between depending on the print project. I understand this means disassembling the extruder, but for now that's ok. i'm also going to redesign the extruder to allow me to swap nozzles easily.

Anyone got any suggestions? i'm still planning about how to build my first 3D printer. I presently borrowed a friend's old reprap Prusa V1, i've just souped up some of its parts to V2 to get rid of wobble and increase print quality, but i'm hoping to build up a new frame which is modullar and easily upgradable. are there any potential pitfalls I should avoid?

Well, they say that a 1.5MM extruder would need twice the strength of a 3MM extruder to push the filament out. If you think about it, it kinda makes sense.

But my recommendation to you would be: try to work with whatever you have, then try to work down to see if you can reach the resolution required.

With regards to the nozzle, I'm sure there are cnc machines who can mill the parts out of a block alu/brass, but I don't know if anyone has actually tried to make and use one with success.

[forums.reprap.org]
[hydraraptor.blogspot.de]

Hope these help.

SW