Multiple secondary target points

RLD89 · Feb 21, 2017

When using datum targets on a flexible part with a complex shape, there is no limit to the number of primary target points. Can the secondary have more than two target points?

3DDave · Feb 21, 2017

If it makes sense to use multiple directions of restraint then there is no need to limit the number of them.

pmarc · Feb 21, 2017

From Y14.5-2009, para. 4.20:
"In a restrained application, it is permissible to use as many datum targets as necessary to establish the datum features."

SeasonLee · Feb 21, 2017

There are 4 target points on secondary datum feature on Fig.B-2 Y14.8-2009.

Season

Belanger · Feb 21, 2017

Even in an unrestrained condition, it would be permissible to use more than the usual number of targets. The part may not contact all of them (which is why restraining is often advisable) but maybe full contact isn't needed.

Also, there are instances of a secondary datum needing less than two points of contact -- only one point.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

RLD89 · Feb 21, 2017

Thanks to all for the responses. It clarifies doubts I had.

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Multiple secondary target points

RLD89

Aerospace

3DDave

Aerospace

pmarc

Mechanical

SeasonLee

Mechanical

Belanger

Automotive

RLD89

Aerospace

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