Just one more quick comment on CFM, nozzle size and blasting…
I discussed a little about the differences and relationship between CFM and PSI in a previous post. PSI is basically the amount of force you blast with. CFM is the volume of air being used during blasting.
It is sometimes suprising to realize how much air (CFM) is required during blasting. At a given PSI setting, the amount of air needed is directly related to the nozzle size being used. The larger the nozzle, the more air that is required. This also means that if you want to use a large nozzle, you will need a large compressor.
For example, at 80 psi, a 1/8″ nozzle will require 20 CFM. At the same pressure a 1/4″ nozzle will require 85 CFM and a 1/2″ nozzle will demand 340 CFM. A basic chart that shows the air requirements for different nozzles at different pressures is on the PPB Series page.
Rule of thumb: double the nozzle size, quadruple the CFM required.