I often hear people on the forum ask what diameter a Badger or Omni needle is because they have been exposed to a certain Japanese airbrush company's literature which always lists the needle diameter. The diameter of the needle has nothing to do with how fine it will spray.
The key to the needle and fine lines is the grade to the tip (how gradual the needle comes to a tip). The more gradual the angle (sharper the point) the finer the line the airbrush will create. This is why if you look at the grade/point on the fine needle of the Sotar you will find it to be the sharpest needle point on the market, which is what enables it to create the finest line achievable. Most people want to know the size of the opening of the tip. They think this has something to do with the fineness of the line, when in fact all the opening of the tip notably effects is the allowability of varying viscosities of material and varying particle sizes (usually pigment) to pass through it and how much overspray an airbrush will create. This is why the tip openings on the Badger 155s, 200s and 360s are the slightest bit larger - because it provides more forgiveness for larger pigments and heavier viscosities, hence it is more forgiving and will clog less. The 100s, 150s, 200-20, and Sotar on the other hand have smaller openings and will be more sensitive as far as clogging goes, but they give less overspray (tighter, not finer lines). There is also the factor of how the grade of the needle plays into the equation. A needle with a more gradual angle to the tip (sharper/pointier) will also lead to more clogging. Hence the Sotar again is more sensitive in regard to clogging. This is why Badger engineers designed the step angles on the 155, 200, and 360 needles - the dual step in grade to the tip further lessens the likelyhood of clogging, yet still allows for precise atomization. These guns (155, 200, 360) are for more general applications and are far more foolproof because of their designs. The 100, 150, 200-20 and especially the SOTAR, because of their tip/needle designs are more detail oriented.
This is the most common misnomer related to airbrushes and their line fineness, but you can see why Badger generally has given up on trying to explain this to people who unknowingly think all that matters is the size of the paint tip opening. Because Iwata's is smaller they think the Iwata airbrush is better, when in fact there is far more to it and the Iwata is more likely to clog and often times does.
My thanks to Ken Schlotfeldt at Badger for enlightening me to these facts.
Mike
“Wisdom is the right use of knowledge. To know is not
to be wise. Many men know a great deal, and are all the greater fools
for it. There is no fool so great a fool as a knowing fool. But to know
how to use knowledge is to have wisdom. " Charles Spurgeon