Basic dimensions of hole pattern

[310toumad]

The usual convention shown for dimensioning holes located on a bolt circle is by assigning a basic dimension of the angle between the holes times the number of instances. My question is would it be valid to have the basic dimension be the relative center distance of the holes rather than using the angle between them?

 

[MintJulep]

It's just geometry.

https://en.wikipedia.org/wiki/Chord_(geometry)

 

[chez311]

Basic dimensions are theoretically exact dimensions. As long as you relate the true position of your holes back to your DRF, these basic dimensions can be in just about any configuration imaginable - though of course there are some that are more easily interpreted than others. This can be polar (radius/angle) or cartesian (x,y coordinates) or something entirely different. The choice is yours as a designer to determine what is best in a particular circumstance.

 

[pmarc]

Snapshot taken from ASME Y14.5-2009: