Different focus lenses

[lezervago]

Hi All,

Can you help me, what is the practical difference of the different F38,1/50,8/63,5 lenses?
What are each ones advantage/disadvantage?

I want to cut nylon webbing, with the possible nicest edge (with less melted/thickened part).

thanks

[SWMS]

Your answe albeit complicated is here
http://www.parallax-tech.com/faq.htm

Basically the narrower the beam the more accurate it is and more powerful but there is a trade off as the useable thickness of cut is less. Good for cutting hard thin material

Likewise the thicker the beam the thicker the cut but it's less powerful and less accurate. Good for less dense thick material.