What is the best method for inspection of a large partial radius? Does anyone know of technical publications or articles on radius measurement uncertainty? We have a lot of parts that have radii that are less than a quarter of the complete diameter. Most of the radii are between 5 and 8 inches and have tolerances that are as low as plus or minus .002". The problem is that if the radius is large and you have just a small portion of the radius, and unless the radius has perfect form, most measurement software, cmm's, comparators will give a reading based on best fit of points which will not be repeatable. This is something we struggle with on a weekly basis. I have been trying to find technical papers/publications on the uncertainty of this type of measurement and would think that this has been researched but so far unable to find anything.