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Unlike MSS, for the Composite Feature Control Frame the top and bottom operate together. It is shown to be a composite tolerance because there is one geometric symbol that spans across the two frameworks. Feature Control Frame is placed in a note, chart, or tolerance block Composite Feature Control FrameĪ Composite Feature Control Frame (FCF) contains two tolerance zone frameworks. Feature Control Frame is attached to an existing frame this is generally used for refinement.į. However, if it is NOT directly in line with the dimension then it is controlling just the surface associated with that extension line.Į. Take extra care to note that if the feature control frame is directly in line with the dimension, it is controlling that feature of size. Feature Control Frame is attached directly to dimension extension line of feature. This is controlling the surface associated with the leader line.ĭ. Feature Control Frame is attached directly to extension line of feature. Both instances shown here are controlling just the surface.Ĭ. Feature Control Frame is attached to feature (or extension line relating to the feature) using leader arrow. Feature Control Frame is located directly underneath or next to note/dimension of a feature. How the feature control frame is placed on the drawing will determine if the geometric control is on a feature of size (FOS) or a surface.Ī. The feature control frame can be placed on feature of size and surfaces. Below is how you would read the frame in order to describe the feature.īe sure to check out our individual pages for each GD&T symbol for examples and specific uses of the feature control frame. The feature control frame forms a kind of sentence when you read it. During measurement, this is the datum fixated last. This letter corresponds to a feature somewhere on the part which will be marked with the same letter.
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Secondary Datum Feature Reference (if required) – If a secondary datum is required, it will be referenced to the right of the primary datum feature reference.Note: The order of the datum is important for measurement of the part. This is the datum that must be constrained first when measuring the part. The letter corresponds to a feature somewhere on the part which will be marked with the same letter. Primary Datum Feature Reference (if required) – If a datum is required, this is the main datum feature used for the GD&T control.See the Modifiers section of the GD&T Symbols page for further clarification on these features. Feature of Size or Tolerance Modifiers (if required) – This is where you call out any tolerance modifiers in the feature control frame.The unit of measure is based on the drawing standard.
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Tolerance Value – The TOTAL tolerance of the geometric control.Diameter Symbol (if required) – If the geometric control is a diametrical tolerance, then the diameter symbol (Ø) will be in front of the tolerance value.See our page on GD&T symbols for a description of each symbol. Geometric Symbol – This is where your geometric control is specified.Leader Arrow – This arrow points to the feature that the geometric control is placed on.
#DATUM FEATURE SYMBOL HOW TO#
This information provides everything you need to determine how the geometrical tolerance needs to be interpreted and how to measure or determine if the part is in specification. Datum references (if required by the GD&T symbol).Tolerance zone modifiers: material condition modifiers, projections….The feature control frame consists of four main pieces of information: A feature control frame is used in GD&T to describe the conditions and tolerances of a geometric control on a part’s feature.