"The datum feature of the linear extruded shape
shown in Figure 7-3, illustration (f) establishes a true
geometric counterpart that creates a datum plane and
a datum axis and constrains five degrees of freedom
(two translational and three rotational)."
I know that, concerning the Slot. My question is, it is possible to take the hole + the slot to create a DATUM REF. Like to if you have 4 holes together. As Shown in the link
What will be controlled by this slot-hole datum system? Why would you do that?
Edit: you could separate the slot and hole. The width of the slot would be Datum B (wrt to A) and the axis of the hole would be Datum C (wrt to A|B). Then the feature you want to control calls out A|B|C and it locks all 6 degrees of freedom.
The hole doesn't add anything to the equation regarding the DRF. Use datum targets A1 and A2 on slot&hole respectively if you can't comprehend the ABC concept.
Is it appropriate functionally to use the hole & slot as a single reference?
Typically in such cases face A will constrain 3 degrees of freedom, the hole additional 2, and the slot will lock the last rotation. Then it's A,B,C as suggested by Whuzhee. Or if from some reason you want to unite the two references anyway you can use the "common datum features" concept as in my deleted post above.
I wouldn't use the hole or slot as primary datums. Part of the skill of selecting primary datums is using surfaces that are large, easy to access or grab. Usually this means outer surfaces. The holes and slot and the mating threaded holes can be positioned using regular positional tolerancing.
If I understand your questions correctly, I would say NO, you cannot create a hole pattern with a hole(Ø10±0.2) and a slot(12±0.2 X 18±0.2), because they are two different feature of size.
In your case, normally we will assign the round hole as the 2nd datum feature and the width of the slot as the tertiary datum feature.
"In a simultaneous requirement, there is no translation or rotation between the datum reference frames of the included geometric tolerances, thus creating a single pattern."
