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26 terms

Lesson 2.2 Key Terms

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Aligned Dimension
A system of dimensioning which requires all numerals, figures, and notes to be aligned with the dimension lines so that they may be read from the bottom (for horizontal dimensions) and from the right side (for vertical dimensions).
Bilateral Tolerance
A tolerance in which variation is permitted in both directions from the specified dimension.
Datum Dimension
A dimensioning system where each dimension originates from a common surface, plane, or axis. Also known as baseline dimensioning.
Dual Dimensions
Where alternate units are displayed within the same dimension (both metric and standard dimensions can shown at the same time).
General Notes
Notes placed separate from the views; relate to the entire drawing.
Size Dimensions
describe the size of each geometric feature
Reference Dimension
A dimension, usually without a tolerance, used for information purposes only. A reference is a repeat of a given dimension or established from other values shown on a drawing. Reference dimensions are enclosed in ( ) on the drawing.
Limits of Dimension
The largest and smallest possible boundaries to which a feature may be made as related to the tolerance of the dimension.
Maximum Material Condition (MMC)
The largest size limit of an external feature and the smallest size limit of an internal feature.
Unilateral Tolerance
A tolerance in which variation is permitted in only one direction from the specified dimension.
American National Standards Institute (ANSI)
A private, non-profit organization that coordinates the development and use of voluntary consensus standards in the United States.
American Society of Mechanical Engineers (ASME)
1. A professional engineering organization that is known for setting codes and standards for mechanical devices in the United States. ASME drawing standards are found in the Y-14M publications. 2. The acronym for the American Society of Mechanical Engineers.
Arrowheads
Arrowheads are used to indicate the end of a dimension line or leader.
Datum
an item of factual information derived from measurement or research
Dimensions
length, width, and height
Leaders
the body of people who lead a group
Local Notes
Connected to specific features on the views of the drawing. Also known as annotations.
Tolerance
the act of tolerating something
Baseline Dimensioning
System of dimensioning in which all dimensions are placed from a datum and not from feature to feature. Also referred to as Datum Dimensioning.
Chain Dimensioning
Also known as point-to-point dimensioning where dimensions are established from one point to the next.
Dimension Lines
Lines that are thin lines capped with arrowheads, which may be broken along their length to provide space for the dimension numerals.
Extension Lines
Thin lines used to establish the extent of a dimension. Extension lines begin with a short space from the object and extend to about .125 inches past the last dimension line. Extension lines may cross object lines, center lines, hidden lines, and other extension lines, but may not cross dimension lines.
Nominal Size
The designation of the size established for a commercial product.
Location Dimension
A location dimension that defines the relationship of features of an object.
Least Material Condition (LMC)
The smallest size limit of an external feature and the largest size limit of an internal feature.
Unidirectional Dimension
A dimensioning system which requires all numerals, figures, and notes to be lettered horizontally and be read from the bottom of the drawing sheet.