i have started tig welding and am unsure about the tungsten. i sharpen all of my tungsten on a peanut grinder. i have a tungsten only wheel. do i need a seperate wheel for each different type of tungsten (thoriated, ceriated, lanthanated)? if i contaminate my tungsten do i need to cut off the entire tip or just resharpen it? i have noticed the tip of my tungsten is discolored after i use it. is it contaminated or just too much heat? btw im welding autobody metal and 1/16 sheet metal with an htp 130 dc/hf and 1/16 2% ceriated tungsten. thanks for any help.