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A
A.DelNegro1-Visitor
1-Visitor
September 20, 2010
Question

another GTOL question

  • September 20, 2010
  • 2 replies
  • 1034 views
I was able to show the axis datum, finally as shown here.





The question is, I have a drawing with the datum as shown below. Is it
possible to create a datum like this?



And what is the difference between this and what I have above? The
datum below is referenced in a run-out tolerance.







I was able to create the dim attached to a dim. like this... but not by
itself like above.







Thanx again,

Tony



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2 replies

P
ptc-19327451-Visitor
1-Visitor
September 21, 2010


In the drawing example above, the datum is attached to a surface edge
and not the dimension (I assume). I think this only makes sense if the
surface is flat and shown edge-on. If the surface shown is actually
part of a cylinder or cone, the dimension should be attached to one of
the dimension leaders, the feature centerline, or if not a cone or
cylinder, the datum should be attached to a form or profile feature such
as flatness, circularity, cylindricity, or profile of a surface.





If attached to the dimension leader, this would define the datum as only
being confined to the surface that is being dimensioned for size. If
attached to the overall component centerline, I think that you would
need to still define datum locator targets and/or zones as required,
because the part is not one continuous diameter throughout its length.





I would suggest that this is probably what was wanted originally. This
confines datum A to the center axis of the 3.000 diameter portion of the
component. As a thought experiment, I would re-create this datum by
chucking this diameter in a collet or other self-centering device that
contacts the part on the entire 3.000 diameter cylinder only.



Just my $0.02,





Christopher F. Gosnell



FPD Company

124 Hidden Valley Road

McMurray, PA 15317
B
bkurth10-Marble
10-Marble
September 21, 2010

Anthony,

Depending on what you want to do, you can change how your gtol is displayed within your drawings by changing the gtol_datums setting in your Drawing Options.

Right-Click in an open area of your drawing, Click Properties >> Drawing Options. Then scroll down until you see thegeometric tolerancingarea (shown in attached image). We use ISO by default, but if you change to ASME, for instance, it will directly change how your gtol is applied when using it around a diameter, as you are showing. You should check on what standards your company is using, though, as this setting will change other display characteristics, as well.

Brian

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