1.2 DEFINITIONS

 

Accuracy - The expected ability for a system to discriminate between two settings.

 

Assembly - the connection of two or more separate parts to make a new single part.

 

Basic Dimension - The target dimension for a part. This typically has an associated tolerance.

 

Dimension - A size of a feature, either measured, or specified.

 

Dimensional Metrology - The use of instruments to determine object sizes shapes, form, etc.

 

English System - See Imperial.

 

Error - a discrepency between expected, and actual values.

 

Imperial System - An older system of measurement, still in use in some places, but generally replaced by the metric system.

 

Limits - These typically define a dimensional range that a measurement can be expected to fall within.

 

Machine Tool - Generally use to refer to a machine that performs a manufacturing operation. This is sometimes confused with the actual cutting tools, such as a drill bit, that do the cutting.

 

Measurement - The determination of an unknown dimension. This requires that known standards be used directly, or indirectly for comparison.

 

Metric System - A measurement system that has been standardized globally, and is commonly used in all modern engineering projects.

 

Metrology - The science of measurement. The purpose of this discipline it to establish means of determining physical quantities, such as dimensions, temperature, force, etc.

 

Precision - Implies a high degree of accuracy.

 

Repeatability - Imperfections in mechanical systems can mean that during a Mechanical cycle, a process does not stop at the same location, or move through the same spot each time. The variation range is refered to as repeatability.

 

Standards - a known set of dimensions, or ideals to compare others against.

 

Standard Sizes - a component, or a dimension that is chosen from a table of standard sizes/forms.

 

Tolerance - The allowable variation in a basic dimension before a part is considered unacceptable