I need them to buy them. and to work them as I say instead of how they indicate standards.
then use to make finished components.
flange is just part of my product.
I look for crude, therefore from the moulders, because the processing of flanges is an eye-to-eye processing to say it in a bonario way.
they have absurd tolerances, and the pieces come crooked.
if I need a tenth tolerance that already in mechanics is an eternity., the tolerances of the flanges are at the millimeter
if the uses for piping also regulated (e.g. asme b31.3), those which are on the market and built according to b16.5 have adequate tolerances for the purpose and there is no need to modify them.
if you use it for other applications or always for piping but not standard (e.g., you have special holes for certain components that are also out-of-standard or built according to other standards) and you have no big numbers, you could get it from full: depends on how much and what you have to change compared to the std flange.
in any case modify a standard component and - especially if subject to pressure - you must make your alternative evaluations regarding resistance.