DATUM REF 5 DEGREES OF FREDOM

[nry67]

it is possible to create a DATUM REF with 1 slot & 1 holes together to remove the 5 degrees of freedom. DATUM REF B in the figure linked

 

[Wuzhee]

A slot constrains 5 deg of freedom.

"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)."

 

[nry67]

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

 

[Wuzhee]

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.

 

[nry67]

My initial question was it is possible to create a Datum Reference Frame (DRF) with only A and B for my assembled
As the example.

 

[nry67]

 

[Wuzhee]

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.

 

[Burunduk]

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.

 

[jassco]

Hi, nry67:

The hole (10mm) and the slot (12mm) are two different features. It does not make sense to label them as datum feature "A".

Best regards,

Alex

 

[Eric Gushiken]

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.

 

[DanStro]

Are you asking about creating a custom DRF? Like something shown in fig 4-46 of 14.5 2009?

 

[SeasonLee]

nry67

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.

Season

 

[3DDave]

ASME Y14.5-2018 7.19, SIMULTANEOUS REQUIREMENTS

"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."