Block tolerance does not apply and the applicable tolerance will be given A basic dimension is alway associated with a feature control frame or datum target.
GD&T Geometric Dimensioning and Tolerancing terms and definitions.Īctual Size - Actual size is the measured size of the produced feature.Īngularity - Angularity is the condition of a surface, axis, or centerplane, which is at a specified angle (other than 0, 90, 180 or 270 deg.)īasic Dimension - A basic dimension is a theoretically exact value used to describe the exact size, profile, orientation or location of aįeature.
#Simulated datum iso#
GD&T Symbols, ISO G&T Symbols 1101 DefinitionsĮngineering Design Manufactuirng Definitions and Terms Likewise, a "true" True Geometric Counterpart of a cylindrical actual feature would have to be of a diameter value which is precise to infinite decimal places.Geometric Dimensioning & Tolerancing GD&T Symbols & Definitions To fully represent the TGC, an infinite number of points would need to be scanned with perfect precision.
#Simulated datum simulator#
A plane simulator or a datum plane tangent to a portion of the scan considered as the planar datum feature may contact the 3 high points on the cloud of points, but it may not properly represent the plane which would contact the 3 highest points on the actual surface that was scanned.
#Simulated datum software#
I would say that the simulators established by the software have perfect form and perfect relationship to each other, but an indirect and imperfect relationship to the actual surfaces of the datum features. that have perfect form and perfect relationships to each other. It's interesting because the geometric counterparts established by coordinate metrology devices are perfect - the software defines perfect planes, perfect cylinders, perfect parallel-plane widths etc. RE: Datum Feature Simulator - definition Vs. It's like someone was paid by the word and no one made a map. With the corresponding true geometric counterpart," "If irregularities on a datum feature are such that the part is unstable (i.e., it rocks) when it is brought into contact "When magnified surfaces of manufactured parts are seen to have irregularities, contact is made with a true geometric counterpart at a number of surface extremities or high points." Being theoretical there can be no contact seen by magnification. This however, is a place it runs off the rails from deep in 7.6: That clarification would not be required if "datum" was still in the term. True geometric counterpart doesn't help cement that place in the hierarchy.įrom the foreword: "The use of the “true geometric counterpart” term is limited to datums." I preferred the previous term - "theoretical datum feature simulator" as it bridged the gap from datum feature to theoretical datum. Note that step 3 can either use best-effort gauges or best-effort measurements.
I'm trying to figure out what reasoning has led you to believe the train has left the tracks, seriously.Ģ) (Theoretical) True Geometric Counterpart that is aligned to the three planes.ģ) (Not theoretical) Datum feature simulator that is the imperfect not-theoretical best effort approximation as an approximation of the True Geometric CounterpartĤ) (Part) Datum feature that is aligned to the applicable Datum feature simulator Photons are physical enough I keep seeing really attractive deals on photon wood cutters.
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