With glow-in-the-dark filament, you can go thru 2-3 spools before having to replace the brass nozzle.
With metallic filaments, you may have to replace at just a 1/2 to 1 spool.
There are also harden steel nozzles available that will last much longer. ($10-25)
There will also be a gemstone nozzle available soon, that is supposed to last forever ($75-90)
The new nozzle has a perfectly cylindrical bore in the tip, and a flat bottom. This allows for a smooth extrusion, that is “struck-off” flat, on the surface of the plastic.
The worn nozzle has rough edges inside the bore, and a slightly round bottom. The grooves will cause the appearance of “striations” on the surface of the plastics, and will not only NOT be “struck-off” flat, but will also cause the filament to stick to the rounded edges, and cause some “lifting”, as the extruder moves across it. This may also cause some uneven “bulging” at the edges of the surface layers, b/c extrusion is not be controlled consistently at the outer perimeters.
Use a fine-tooth metal file, and lightly hand file off the roundness at the tip. 1 perfectly flat stroke is all that is needed, then a few angled strokes, (with the nozzle profile), to remove an burrs.
Start with a .4mm drill bit, and work your way up, until there is resistance to hand drilling.
Use digital calipers to measure the last drill bit that you used.
Re-set your slicer’s “nozzle diameter” to the new bore diameter, and you have a perfectly good nozzle to use.
Unless you are printing highly detailed objects, the small amount of additional “layer banding” is hardly noticeable.
BUT, as with everything in this hobby, changing one parameter(nozzle diameter), means having to make other adjustments as well. (this is “the art” of 3d printing)
Small nozzle diameter is great for highly detailed print objects, but plastic is being restricted from moving too fast thru the orifice, that means having to reduce extrusion speed and temperature(since you don/t want to cook the filament for too long).
Larger nozzle diameters are great for reducing print time, and increasing the strength of a printed object,b/c it will produce wider “extrusion widths”. Now you can increase the extrusion speed, since there is less restriction of plastic moving thru the orifice. Increasing speed, also means having to increase extrusion temperature, just to keep up with the volume of plastic moving thru the nozzle. Quality is decreased, but that doesn’t matter if your print object is more mechanical, than aesthetic.
Basic “rule-of-thumb”: Nozzle Dia. x 1.2 = plastic extrusion width
.4 nozzle = .48 extrusion width @ 0.2mm layer height
.5 = .6 @ 0.3mm
.6 = .72 @ 0.4mm
The math, shows that the aesthetics of the outer layers starts to deteriorate, even thou the strength of the object is increasing.
So using the term “quality of a print” , is subjective, given the print objects desired outcome, “Pretty vs Strong”