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Fundamentals of Graphics Communication, 3/e
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Bertoline - Fundamentals of Graphics Communication Third Edition

Glossary N-O

Please click on the desired term below to view the glossary definition.
NC  (n) Acronym for numeric control, a form of programmable automation of a machine tool, using numbers, letters, and symbols. Unlike on an engineering drawing, the part geometry must be defined using coordinates instead of graphics. All NC systems today use computers and are called computer numerical control (CNC) machine tools.
negative space sketching  (n) A technique where you concentrate on sketching the space between the objects and not on the object itself.
networked hierarchy  (n) A hierarchical parts structure used by modeling systems. In a networked hierarchy, parts can be shared across assemblies by means of software links set up external to any one file. These parts structures are often managed by special database software networked across workstations within an organization.
nominal scale  (n) A qualitative data scale that has no inherent order to it (e.g., New York, Boston, and Houston).
nominal size  (n) A dimension used to describe the general size of an object, usually expressed in common fractions. For example, a bolt might have a nominal size of 1/2".
nonhierarchical  (n) A structure in which elements may be sorted into separate groups, but there is no defined linkage or ordering of the groups. Layering in CAD systems is often defined as being nonhierarchical.
nonisometric line/plane  (n) A line or plane that is not parallel to one of the principal isometric axes or to two adjacent isometric axes, respectively. In an isometric drawing, nonisometric lines and planes are typically more difficult to draw than isometric elements.
nonuniform rational B-spline  (n) See NURBS.
normal  (adj. or n) A term describing a direction perpendicular to a planar surface, or a vector representing a perpendicular direction. Normals are used to calculate the orientation of a surface with respect to a light source or view point.
normal edge/line  (n) An edge of a face parallel to a plane of projection and perpendicular to the adjacent orthogonal planes. The edge appears as an orthogonal, true-length line in two of the principal views and as a point in the third view.
normal face  (n) A planar surface of an object that is parallel to one of the principal image planes. A normal face is seen in its true size and shape in the image plane to which it is parallel and is seen as an edge in the other two principal image planes. The normal face is named for the image plane to which it is parallel.
nuclear engineering  (n) A field of engineering that includes all areas of research, development, and application of nuclear energy. Areas of specialty include reactor engineering, reactor control, nuclear materials, reactor physics, controlled thermonuclear fusion, reactor safety, fuel management, and shielding.
numeric control  (n) See NC.
NURBS  (n) Acronym for nonuniform rational B-spline, a type of free-form curve that uses rational B-splines and allows for a weighting value at each point on the surface. Because NURBS can also precisely describe conic surfaces, they are gaining popularity in tasks previously done with other types of 3-D modelers.
nut  (n) An internally threaded device used on the ends of threaded fasteners to join materials. Nuts are an alternative to threading the part itself and are often paired with a washer to assist in distributing the pressure and/or securing the nut.
oblique  (adj.) A direction that is neither parallel nor perpendicular to a plane.
oblique edge/line  (n) An edge of a face that is not parallel to any of the three primary orthogonal planes. The edge appears foreshortened in all three principal views of a multiview drawing.
oblique face  (n) A planar surface of an object that has been rotated about two axes from one of the principal image planes. An oblique face will appear foreshortened in all three of the principal views. Unlike inclined and normal faces, an oblique face is not seen as an edge in any of the principal image planes.
oblique projection  (n) A form of parallel projection used to create oblique pictorials. Oblique projection results when the projectors are parallel to each other but at some angle other than perpendicular to the projection plane. Typically the most descriptive face of an object is placed parallel to the frontal plane.
offset coordinate method  (n) A construction method used to construct non-normal views of cylinders, circles, arcs, and other curved or irregular features. The feature is first drawn in an orthographic view, and then regularly spaced coordinate points are transferred to the foreshortened view space, where they are connected using an irregular curve.
offset section  (n) A full section view generated by multiple, connected cutting planes that are parallel but not coplanar. This technique is used to allow the cutting planes to pass through a series of features that do not all lie in the same plane.
ogee curve  (n) A curve that connects two parallel lines with two arcs, forming a smooth curve. Such curves are often seen in architectural details.
open loop  (n) A set of edges in a CAD model that does not connect end to end, creating a closed loop. Solid modelers differ as to whether open loops can be used as profiles for feature generation. Open loops cannot be used to define faces on a solid model.
operating system  (n) The software controls the basic functions of a computer system, such as reading and writing files to the disk, communicating with the printer, etc. Common operating systems include UNIX, MS-DOS, and Macintosh OS.
ordinal scale  (n) A qualitative data scale that has an inherent order. Even though ordinal data has an order, the order is not quantitative because the individual data elements are symbolic and have no inherent magnitude.
orthographic projection  (n) A parallel projection technique that creates a 2-D image of 3-D objects or structures on an image plane perpendicular to the lines of sight. The orthographic projection technique can produce pictorial drawings, such as isometric or oblique, that show the three dimensions of an object or multiviews that only show two dimensions of an object in a single view.
outline assembly  (n) A general graphic description of the exterior shape of an assembly. Outline assemblies are used for parts catalogs and installation manuals or for production when the assembly is simple enough to be visualized without the use of other drawing techniques, such as sectioning. Hidden lines are omitted except for clarity.
output device  (n) A peripheral hardware device linked to a computer that allows information in the computer to be accessible to the human senses. Common types of output devices include computer monitors and printers.