Hi all,

I am having a debate with a coworker and which method means what in relationship to the datum and to the other holes

the way I understand it the top method means nothing is positional more than 0.1 from the datum

the bottom one means the hole patterns can be 0.1 from the datum and each hole set can be a additional 0.1 from the datum.

Hopefully I explained this well enough and not cause world war 3 for designer/engineers but would like some more input as I do not see this specific thing covered in ASME Y14.5

regards,

As I understand it, basic dimensions are theoretically exact. Since the position tolerance of both of your patterns are all the way back to datums A, B, and C, there is no tolerance stackup when you add the values of the basic dimensions. The [25.00] + 2x[75.00] in the second drawing means exactly the same as the [175] in the first one.