GD&T Datum reference frame
Mufaddal Rasheed 
What does Datum reference frame mean? How is it formed in GD&T ?
As in co-ordinate geometry , there is always a reference system with respect to which dimensions are referred from or measured from.
GD&T also uses similar concept In the Datum reference frame system when establishing interrelations between features.
Here the reference frames are formed by features of a part which maybe planar features of features of size.
When Datum notations are applied to features, that feature is called as the datum feature and it will have datum planes associated with it.
Datum reference frame is formed by creation of datum planes for each datum feature
Consider this drawing
There are three datum features which primary, secondary and tertiary datum features.
The corresponding datum planes (which are theoretical) if intersected – as shown in the pink color . They form together the datum reference frame
The intersection point between all the three datum planes is nothing but the origin of the datum reference frame.
Here is another example.
The datum reference frame for this component would look like this .
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Categories: : GD & Tolerancing