TP of slot on diameter 1

[fineout]

Hi ,
this is always a problem for me conceptualizing and I decided to finally try and get some help. I get a lot of prints coming through with tabs, slots, punches, etc somewhere along the radius of a circle and then called out with a true position to the circle but with no other refrence to use as a datum for any angle or something. I have no idea how to get a number because it seems like if its along the circle its ok, or is it that the centerline of the slot has to be straight enough to pass through the center of the circle?

 

[KENAT]

"or is it that the centerline of the slot has to be straight enough to pass through the center of the circle" - more or less - the positional tolerance zone is centered on a plane through the center of the datum diameter.

Someone forum1103 may be willing to give a more detailed response, in fact that may be a better place for GD&T interpretation questions.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[Belanger]

I agree with Kenat. Datum A is the center axis of the inside diameter, as determined from its "maximum inscribed cylinder."
Then, the center plane of the tab must lie within two imaginary planes spaced 0.02 apart (if the tab's at MMC). This 0.02 "tolerance zone" must be perfectly centered around datum axis A.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems