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never seen this before - is it right?

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duk748

Mechanical
Jul 18, 2007
167
hello - i received a drawing from a vendor of a plate that has a tapered diameter at the front of it - i am attaching a sketch of the plate because of company rules - the datums on the tapered surface are angular and flatness - i dont think this is right - if it is i have never seen this used like this before - i would have thought that maybe profile would have been better suited - the tapered nose fits into a mating piece and has to have little or no gap when assembled - thank you in advance[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1687027076/tips/taperdatum_a6vbph.pdf[/url]
 
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Without an angle angularity is a reach unless they think it applies to an axis - which is a case not specifically defined for tapered features. Flatness also would not appear to apply.

Ask the vendor for some examples of extreme limits of variation they think this scheme will allow.
 
Are the flatness and angularity applied by a leader to the conical surface outline?
Can you show a sketch of the callout exactly as it is on the drawing instead of the explanation note?
 
Hi All,

I agree that if this is a conical feature, neither flatness nor angularity can be applied directly to the surface. Perhaps the intent was to control the form and orientation of each cross section. This could be achieved using straightness and angularity with the EACH ELEMENT annotation. Also, the form tolerance should be smaller than the orientation tolerance.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
 
hello and thank you for the replies - yes the datums are shown with a leader attached to the tapered surface - i also think that without an angle dimension the angularity is useless - i would have thought that possibly a diameter as a datum then an angle dimension as basic - just my thoughts - thank you for the help - i will contact the vendor and report back as to what i find
 
Jargon - those are Feature Control Frames, not datum feature symbols.
 
Angularity can't be used to control the included angle of a cone (Edit: unless EACH LINE ELEMENT note is used, as mentioned by Evan, and a datum is referenced). Angularity is mainly intended and able to control orientation of a flat surface or cylinder axis relative to a datum feature.
 
Flatness definitely wouldn't be valid. Angularity seems valid. Another way to control that angled surface is with profile. If the entire part is circular they might even be able to use total runout.
 
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