# How to deal with Multiple Datums - Position with respect to Multiple Datum Feature

O

#### Omar.

Hello everybody.

my question is:

If I have a call out of a position with respect to multiple datum feature
(A-B). I undestand that A and B would act as one datum. But for example if I would want a basic distance, where does the distance come from? from datum A, from Datum B or from a middle point?

Additionally, multiple datums can only be datums that they are on the same plane? I mean that they have the same vector (normal)?

Omar R.

#### optomist1

##### A Sea of Statistics
Super Moderator
Re: How to deal with Multiple Datums (GD&T)

drawing or image would help

#### Stijloor

Staff member
Super Moderator
Re: How to deal with Multiple Datums (GD&T)

Hello everybody.

my question is:

If I have a call out of a position with respect to multiple datum feature
(A-B). I undestand that A and B would act as one datum. But for example if I would want a basic distance, where does the distance come from? from datum A, from Datum B or from a middle point?

Additionally, multiple datums can only be datums that they are on the same plane? I mean that they have the same vector (normal)?

Omar R.

Datum features that are called out with an hyphen between them are always used simultaneously. For example, two cylindrical datum features may be utilized to create a datum axis. An axis can be viewed as the intersection between two perpendicular planes. Depending on the degrees of freedom that must be constrained, additional datums may be required.

Provide us with a drawing and a reference to the appropriate GD&T Standard if possible.

#### leftoverture

##### Involved In Discussions
Re: How to deal with Multiple Datums (GD&T)

Agree with the others, if you can provide a screen shot fo the particular callout, it would be easier to help.

O

#### Omar.

Re: How to deal with Multiple Datums (GD&T)

Hello All,

I am attaching a ppt explaining in detail my las questions.
I would really appreciate your help guys.

Regards.

Omar R.

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#### optomist1

##### A Sea of Statistics
Super Moderator
Re: How to deal with Multiple Datums (GD&T)

Omar, the drawings seems to present more questions than it answers:
-Is there a drawing title block?
-If yes, does ti call out ASME Y 14.5 1994 or 2009
-Is the part non-rigid or rigid?
-From the drawing, the part appears to be a hose clamp, and non-rigid.
-If non-rigid the drawing must identify the location/area of points of restraint, the sequence, the direction of the force and amount of restraining force applied.
-Regarding the question as to what datum the profile should reference, this is typically dictated by the part function and not how the part is manufactured.

Hope this helps some -

O

#### Omar.

Re: How to deal with Multiple Datums - Position with respect to Multiple Datum Featur

Hello Optimist1, thank you for your response.

Actually, that is not my drawing. It is a portion the Y14.5 (pag. 67).

I hope you can help me.

Thx.

#### optomist1

##### A Sea of Statistics
Super Moderator
Re: How to deal with Multiple Datums - Position with respect to Multiple Datum Featur

1994 or 2009?