Possible illegal gd & t callout

I believe I've stumbled across an incorrect use of Runout to a Flat Datum-A-Plane.
Imagine a bolt with a flat head: this is called out as Dat -A-. It also has a Flatness callout to itself, which is fine. The threaded shaft has a Runout callout to Datum -A-. This I believe is incorrect. If the pitch diameter of the threaded shaft was described as Datum -A- with the flatened side of the bolt head having the Runout callout, this would be correct. Am I correct? I just want some verification.

Nano Vujkovic over 10 years ago

Can you post the print?
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Shane-o over 10 years ago

No, sorry
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Nano Vujkovic over 10 years ago

If i understand it correctly, i believe it is a valid callout.
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Shane-o over 10 years ago

How can a flat plane marked as datum a have a perpendicular threaded shaft with a runout callout to datum a.
If the shaft was adatum a and i needed to check the runout of the flat plane to the threaded shaft i could understand this, then i could put the threaded shft on a v-block and put an indicator on the flat surface and check runout that way. But its
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Shane-o over 10 years ago

Callout to me is backwards and doesnt make sense
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Nano Vujkovic over 10 years ago

Don't mix concentricity with runout.
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Shane-o over 10 years ago

Also Screw thread rule: Tolerances of orientation and position and any datum reference applied to the screw threads apply to the axis of the pitch cylinder.
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Shane-o over 10 years ago

The datum construction is incorrect by calling out the flat screw head as datum a
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Nano Vujkovic over 10 years ago

The datum construction is incorrect by calling out the flat screw head as datum a

Why do you say that? You can make datum any feature on the part. Usually they would be contact surfaces. but not necessarily.
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Shane-o over 10 years ago

Maybe on bigger parts, this is typically a rule due to the fact that the external thread is
plays a mojors role in part functionality , especially with screws. have you heard of this rule before?
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