How to dimension compound curves and compound angles to those curvese GD&T

[bear9298]

What is the proper GD&T dimensioning/callout for drilled holes that are at an compound angle to datum "A" but you want the holes to be perpendicular to the sweeping contoured surface...

 

[drawoh]

bear9298,

What you want is to have your holes perpendicular to a curved face, right? Each hole will be at its own angle in[ ]3D.

What really matters here? Is it perpendicularity to the curved face, or is the curved face coincidentally perpendicular to where you put the hole? How are you going to inspect this thing?

--
JHG

 

[bear9298]

Thanks "drawoh" and yes curved face.. it is a rectangular pad, base being datum "A" with a cylindrical profile along the top face.. "kind of like laying a 6" dia tube down onto the top surface of the base plate" want the 6 holes and spot faces to come in from the top direction at a compound angle to datum "A" but to be perpendicular to the curve at the point of contact... make any since?

 

[bear9298]

drawoh.... sorry.. inspect! I would think it would be to datum "A", "B" and "C" with the curved face a datum.. "D"... that help?

 

[drawoh]

bear9298,

Your datums are your fixturing points. You can pick up your curved face using datum targets. Otherwise, it does not make a good datum. A curved face defined by datum targets does not provide a reference for perpendicularity.

My second paragraph was about priorities. What is more important, the holes or the curves? Your datums, your tolerances and your dimensioning should be based on your requirements, how you part will work, and on how you will inspect it.

--
JHG

 

[bear9298]

drawoh... important.. the holes.. a bolt goes thru the hole in the top plate then thru the part and thru a back up plate and a nut is put on the bolt.. washer on both ends... I can get the counter bored faces to the holes but the holes to the contoured surface was where I failed... Follow you on the Datum targets but the holes perpendicular at the contact point on the curves face??? Hope I'm not going in circles here. apologize if I am... Thanks drawoh for all your time and explanation.