【转帖】holes normal to contour

yang686526

holes normal to contour.
i came across a drawing that specifies in one of their notes
as follows,- all holes normal to contour within 0 degree
30'-. is this legal per asme y14.5 m-94?
is not profile of surface the right call out?

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rmaki,
   i would not regard the note as legal, as per asme y14.5m-1994.
   if perpendularity to the contour is what really matters, they could call up the contour as a datum, and specify that the holes are to be perpendicular to it.  what kind of a contour is it, and how are you going to make the inspection tools?
   i would use true position and possibly angle to locate the holes to a fixturable datum, and put a profile tolerance on the contour.  i would think that locating the contour to the holes would be easier then vice versa.
                            jhg
drawoh, i'm sorry i did not make myself clear in my post.
but,think of a windshield frame in a "u" shape 3".00 wide with a hole pattern of 65 holes all around ( sorry can not provide a dwg),the inspection will be on a inspection check fixture.
rmaki,
   that is not far off what i was visualizing.
   you can specify anything you want on your drawings, but if you cannot inspect it, you cannot control it.  my interpretation of your original note is that the contour is being used as a datum.  if so, your inspection tool will have to model your contour, probably at mmc.  
   are you trying to inspect the contour, or the holes, or both?  this affects how you do your drawings.
                    jhg
what they want to control is "both" contour and the holes.
contour have to be within the profile of the the mating part
and holes need to be at mmc in order to fit.
i never saw a call out like this one before. i think that true position will be the correct call to control the hole pattern to the contour datum.     
... which should then be controlled relative to three primary datums.
the edge... there is no honest way to explain it because the only people who really know where it is are the ones who have gone over.fff"> - hunter s. thompson

yeah, i'd probably control the 'profile' of the part using profile of a surface.  i'd then look at using position for the holes.
all related back to datums as ewh point out.
if the 'circular' portion of the u can be made a datum that may help with the perpendicularity of the holes on that surface.
kenat,