Profile Tolerance Question

[zumkatze]

Hello,

I have a customer's drawing of a sheet metal part with a flange bent at a 91 degree angle from the top surface. On this flange surface, they indicate two Datum B points with the top surface as Datum A. Also on the flange surface, they have a GD&T profile callout of .060 to A, B, & C (a point on an edge).

My question is: Does a profile callout include the datum surfaces too? Or are the Data constrained (A, B & C) and the profile is checked on all non-datum surfaces?
Thanks in advance

 

[drawoh]

zumkatze,

A profile callout normally requires datums. You need somewhere to measure from. You should inspect the surfaces that are controlled by the profile specification, i.e. the ones it points at.

JHG

 

[zumkatze]

The customer's drawing is pointing a profile tolerance to a datum. Is it correct to check the profile tolerance of the datum surface itself?

 

[fsincox]

I see no issure with it, it is more a question of how it is done and what, then, did it mean.
Frank

 

[zumkatze]

Personally, I didn't know you could check a datum against itself.

 

[drawoh]

zumkatze,

I have just created a drawing with a profile tolerance aimed at tertiary datum_D. Datum_D is not shown on the FCF obviously because it is the feature being measured. It is at an angle, so perpendicularity is not appropriate. The angle specification is not appropriate because I did not specify the angle.

Now that I think of it, I may just just add datum_D to my specification. One point of tertiary Datum_D contacts the fixture face. The remainder of the surface must be within the profile tolerance of the fixture face.

In most cases your part is orthogonal. You do not need profile to control datum faces. You need flatness to control the primary datum. Perpendicularity to the primary datum will control your secondary datum, and perpendicularity to primary and seondary controls your tertiary datum.

Most of the time, your tertiary datum is not a face. It is one point somewhere on the face.

JHG