How smooth is peanut butter? I want to make 'cookie butter' (cookies, oil,  powdered sugar, Xmas spices).

My food processor doesn't grind the cookies fine enough. It still feels gritty on the tongue. So I am looking at buying a grinder, but I want to make sure it will do the job.

What is the mesh size or size in microns of the particles in smooth peanut butter?

Bonus question: does any one have a chart of size vs mouth feel of various foods?
Madehow.com discusses the entire process of making peanut butter. 


  Peanut butter is usually made by two grinding operations. The first reduces the nuts to a medium grind and the second to a fine, smooth texture. For fine grinding, clearance between plates is about .032 inch (.08 centimeter). The second milling uses a very high-speed comminutor that has a combination cutting-shearing and attrition action and operates at 9600 rpm. This milling produces a very fine particle with a maximum size of less than 0.01 inch (.025 centimeter).
  (Emphasis mine)


However, creating the correct emulsion of fat and particles may have a greater impact. As with ice cream, the fat coats the tongue and helps prevent a grainy texture. 

EDIT:
This report from Micromeritics, a rheological analysis firm, shows the particle sizes of three (unnamed) chocolate bars. However, it has a useful graph of particle diameters. For the smoothest chocolate bar, approximately 50% of particles are smaller than 5 nanometers, and nearly 80% are less than 10. The lowest quality bar has only 25% of particles smaller than 5 nanometers, and only 45% are less than 10.