0004// Definitions of Feature's Properties Part 1

When you using measurement tools (such as profile projector, CMM, vernier calliper), do you know what you actually measure? The reading you measure maybe is actual local size, size of related actual mating envelope, size of unrelated actual mating envelope or etc.

So, today we will discuss about feature's properties. Below are some feature's properties which mentioned in Y14.5-2009:

Feature (1.3.27):

A physical portion of a part such as a surface, pin, hole, or slot or its representation on drawings, models, or digital data files.

Unrelated actual mating envelope (1.3.25.1):

A similar perfect feature(s) counterpart expanded within an internal feature(s) or contracted about an external feature(s), and not constrained to any datum(s)

Related actual mating envelope (1.3.25.2):

A similar perfect feature counterpart expanded within an internal feature(s) or contracted about an external feature(s) while constrained either in orientation or location or both to the applicable datum(s).

Feature axis (1.3.28):

The axis of the unrelated actual mating envelope of a feature. Center plane of feature (1.3.29):

The center plane of the unrelated actual mating envelope of a feature.

Unrelated actual minimum material envelope (1.3.26.1):

A similar perfect feature(s) counterpart contracted about an internal feature(s) or expanded within an external feature(s), and not constrained to any datum reference frame.

Related actual minimum material envelope (1.3.26.2):

A similar perfect feature(s) counterpart contracted about an internal feature(s) or expanded within an external feature(s) while constrained in either orientation or location or both to the applicable datum(s).

Derived median line (1.3.31):

An imperfect (abstract) line formed by the center points of all cross sections of the feature. These cross sections are normal (perpendicular) to the axis of the unrelated actual mating envelope.

Derived median plane (1.3.30):

An imperfect (abstract) plane formed by the center points of all line segments bounded by the feature. These line segments are normal (perpendicular) to the center plane of the unrelated actual mating envelope.

Actual Local Size (1.3.54):

The measured value of any individual distance at any cross section of a feature of size.

I hope this post is useful for you.

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