Basic bolt circle diameter dim. Does it control bolt pattern runout to a center? 1

[mschroeder]

I have a flat disk, 20 holes around, and see so many examples of bolt circle dia's dimensioned as basic with a position on the holes.

Does the basic bolt circle dimension control location to a center hole in the disk used as datum A?

Does the basic bolt circle diameter dimension still allow circular position tolerance zones or are they now constrained to arc shaped zones?

Thanks.

--mschroeder

 

[powerhound]

I agree that we still dimension to the center of the hole but that is to or from a centerline established by the hole feature. All I'm saying is when calling out an angle as in the OP, I think there still should be some real feature to measure the angle from.

Maybe I should use more care in the emoticons I choose. Is that why you took such offense? A simple smiley face probably would probably not have been so bad.

Powerhound, GDTP S-0731
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[CheckerHater]

Powerhound,
I forgot about emoticon already.
I totally agree that it is always better to give clear dimensions feature-to-feature.
But that’s the reason I was trying to convince you guys that implied 90 deg dimension is basic – there is no tolerance accumulation, so calculating 90-20=70 is “lesser evil”.
OP explained that his drawing was incomplete, so the whole argument was probably about nothing anyway. At least we figured out yet another difference between 1994 and 2009 editions.