Craftsman Computer Aided Mechanical Drawing key terms

A parallel projection method in which projectors strike the projection plane at right angles, producing true-shape views of surfaces parallel to that plane and enabling several aligned views of one object.

A placement convention in which the object sits between the observer and the projection plane, so the view from above is drawn below the front view and the view from the left appears on the right.

A placement convention in which the projection plane lies between the observer and the object, so the top view is drawn above the front view and the right-side view appears to its right.

One of the six standard orthographic views of an object, chosen so that the front view shows the most characteristic shape and the fewest hidden features.

A dashed line style used to represent an edge or contour that is not visible in the current view, drawn with short evenly spaced dashes that meet at corners.

A continuous thick line showing the outline and visible edges of an object in a given view; it carries the strongest line weight on a drawing.

A thin line of alternating long and short dashes marking axes of symmetry, centers of holes, and pitch circles of gears or bolt patterns.

The thickness assigned to a line type; heavier weights denote visible outlines while lighter weights are reserved for dimension, extension, hatch, and center lines.

A thin line terminated by arrowheads that spans the distance being measured and carries the numerical value of the dimension, usually placed outside the object outline.

A thin line projecting from a feature to the dimension line, showing exactly which points the measurement refers to and normally separated from the outline by a small gap.

A theoretically exact plane, axis, or point from which dimensions or tolerances are measured, chosen to reflect how the part functions and to avoid stacked tolerances.

A dimensioning method in which all measurements originate from one common datum surface or axis, reducing accumulated error and simplifying inspection of the part.

A dimensioning method in which each dimension starts where the previous one ends; simple to draw but it accumulates tolerance along the chain.

The total permissible variation in a dimension, equal to the difference between the upper and lower limits; it defines how much a feature may deviate from nominal size.

The maximum and minimum permissible sizes of a feature, stated either as explicit values or as a nominal size with plus and minus deviations.

The nominal dimension from which limits of size and deviations are derived; it is the same for both mating parts of a fit and is not itself a permissible size.

The relationship between the limits of size of two mating features, ranging from clearance through transition to interference, determined by the chosen tolerance zones.

A fit in which the tolerance zone of the hole lies entirely above that of the shaft, so a gap always exists between the assembled parts.

A fit in which the shaft is always larger than the hole within the permitted limits, so the parts must be pressed or shrunk together and cannot move.

A control, shown in a rectangular feature control frame, that limits form, orientation, location, or runout of a feature relative to a stated datum.

A rectangular box containing the geometric characteristic symbol, the tolerance value, and any datum references, attached to the controlled feature by a leader or extension line.

A measure of the fine irregularities left by machining, specified on drawings by a symbol with a roughness value such as Ra and any required machining allowance.

A view produced by imagining the object cut by a cutting plane, removing the nearer portion, and showing the exposed cut surface with hatching plus the visible edges behind it.

A thick line, usually with long dashes and arrows at the ends, that indicates where the imaginary cut is taken and the direction in which the resulting section is viewed.

Thin, evenly spaced parallel lines drawn at a consistent angle across cut surfaces in a section view to distinguish solid material from open space.

A section view in which one quarter of the object is removed, showing half the view in section and half in outside view; used for symmetrical parts such as shafts and pins.

A view projected onto a plane parallel to an inclined surface, so that the inclined face appears in true shape and size rather than foreshortened.

The apparent shortening of a line or surface that is not parallel to the projection plane, so its drawn length is less than its true length.

The actual size of an edge or line shown when it is parallel to the projection plane; inclined edges require an auxiliary view or rotation to appear at true length.

A pictorial drawing on three axes spaced 120 degrees apart, with all three axes drawn at full scale, so edges along them appear at true length.

A pictorial drawing in which the front face is drawn true shape and parallel to the picture plane while receding edges are drawn at an angle, usually half scale.

The standard compass-and-straightedge procedures, such as bisecting an angle or drawing a tangent arc, used to build accurate geometry before any CAD tools are applied.

A CAD setting that forces the cursor to lock onto precise existing geometry such as endpoints, midpoints, centers, or intersections while drawing or editing.

A CAD drawing aid that constrains the cursor to a fixed grid or increment spacing, ensuring entered points land on regular coordinates.

A named organizational level in a CAD file that groups related geometry and carries shared properties such as color, line type, line weight, and visibility.

A named group of CAD objects that behave as a single entity, allowing repeated insertion of standard parts such as bolts, symbols, or title blocks.

The CAD workspace where geometry is drawn at full size in real-world units, independent of the sheet on which it will finally be printed.

The CAD layout environment representing the printed sheet, where a title block and annotations are placed and viewports display scaled views of model space.

A window on a paper-space layout that shows a scaled view of model-space geometry; its scale controls how large the part appears on the printed sheet.

The ratio between a drawn length on the printed sheet and the real length of the object, such as 1:2 for a half-size print.

The bordered area of a drawing sheet containing part name, drawing number, scale, revision, material, and approval signatures required for identification and control.

A tabulated list on an assembly drawing giving item numbers, part numbers, descriptions, quantities, and materials for every component in the assembly.

A drawing showing two or more parts in their working relationship, with item balloons and a parts list, used for assembly and service rather than for manufacturing individual parts.

A drawing of a single part giving all information needed to manufacture it: complete dimensions, tolerances, surface finish, material, and heat treatment.

The property of a shape being identical on either side of an axis or plane; symmetrical parts are often drawn with center lines and may use half sections or half views.

The pitch circle on which equally spaced holes for fasteners are located, dimensioned by its diameter and the number of holes rather than by each hole position.