MATSEC AM Graphical Communication key terms

A drawing method that shows a three-dimensional object as a set of separate two-dimensional views, each looking straight at one face, with height, width and depth recorded on different views.

A projection layout in which the object sits between the observer and the plane, so the view seen from the front is placed on the far side, with the plan below the front view.

A projection layout in which the plane sits between the observer and the object, so the plan appears above the front view and the right-hand view is drawn on the right.

An orthographic view obtained by looking horizontally at an object, showing its height together with its width or depth; named by the direction faced, such as front or side.

The view produced by looking straight down on an object from above, showing its length and breadth but not its height; placed below or above the front view depending on the projection angle used.

The horizontal reference line separating an elevation from its plan in a projection drawing; heights are projected from it and distances are measured from it.

Thin construction lines drawn from points on one view to locate the matching points on an adjacent view, keeping features correctly aligned between views.

An axonometric drawing in which the three axes are spaced 120 degrees apart and true lengths are reduced by about 0.816, giving a pictorial view with equal foreshortening on all three axes.

A pictorial drawing using the same 120-degree axis layout as isometric projection but measuring full true lengths along each axis, so the result is slightly larger than a true projection.

A family of parallel projections in which an object is tilted so that more than one face is visible, including isometric, dimetric and trimetric variants distinguished by the angles between axes.

A pictorial method in which the front face is drawn true shape and parallel lines recede at an angle, usually 45 degrees, either at half scale (cavalier) or half depth (cabinet).

Any drawing that shows an object in three dimensions on a flat sheet so that length, breadth and height are all visible at once, including isometric and oblique views.

A drawing system in which parallel lines appear to converge towards vanishing points, so nearer objects look larger, matching how the eye actually sees space and depth.

The point on the horizon line where a set of receding parallel lines appears to meet in a perspective drawing; each direction of parallel lines has its own vanishing point.

The horizontal line in a perspective drawing marking the viewer's eye level; all vanishing points for horizontal receding lines lie on it.

A perspective drawing in which the front face of the object is parallel to the picture plane and only one set of receding lines converges on a single central vanishing point.

A perspective drawing in which a vertical edge of the object faces the viewer, so two sets of receding lines converge on two separate vanishing points on the horizon.

A view showing the cut surface of an object after an imaginary plane has passed through it, with hatching added to the solid material that the cutting plane crosses.

An imaginary plane shown by a chain line with arrows and letters that indicates where an object is imagined to be sliced to produce a section view.

Evenly spaced thin parallel lines drawn at about 45 degrees across a cut surface in a section view to show that solid material has been sliced through.

A section view in which one quarter of the object is imagined removed, so half the view shows the outside and half shows the cut interior, often used for symmetrical parts.

The system of lines, arrows and numerals that states the true size and position of features on a drawing, following conventions so the information is unambiguous.

A thin line with arrowheads at both ends drawn between extension lines to show the extent of a dimension, with the numeral placed above or in a break in it.

A thin line drawn out from the feature being measured so that a dimension line can be placed clear of the drawing, usually with a small gap from the object.

A thin line ending in an arrowhead that points at a feature and carries a note, size or symbol, often used for radii, diameters and small details where a normal dimension will not fit.

The symbol formed by a circle with a diagonal stroke, placed before a numeral to show that the dimension refers to the full width across a circular feature.

The capital letter R placed before a numeral to show that the dimension gives the distance from the centre of an arc or circle to its edge, not across it.

The fixed ratio between a length on the drawing and the real length it represents, written for example as 1:2 for a reduction or 2:1 for an enlargement.

A flat measuring instrument with several graduated edges marked in different proportional scales, allowing distances to be read directly at the chosen drawing ratio.

The standard meanings given to different line styles, such as continuous thick for visible edges, dashed for hidden edges, chain for centre lines and thin continuous for construction work.

A line of short evenly spaced dashes used to show an edge that exists but cannot be seen from the direction of view, omitted where it would clutter a dimension.

A thin line of alternating long and short dashes drawn through the axis of a symmetrical feature such as a hole, cylinder or circle to mark its centre.

Thin light lines drawn first to establish positions, angles and proportions before the final outline is drawn, and normally left visible or lightly erased.

A triangular drawing instrument, usually supplied as a pair at 45 degrees and 30/60 degrees, used with a T-square or drawing board to draw lines at fixed angles.

A drawing instrument with a long straight edge and a cross head that slides along the edge of the drawing board to guide horizontal lines and support set squares.

The geometric construction that divides a line or angle into two equal parts, usually done with arcs struck from each end at a radius greater than half the length.

A line or plane meeting another at exactly 90 degrees; constructed geometrically by striking equal arcs from two points and joining their intersections.

The condition where a line or curve touches a circle or arc at exactly one point, with the radius at that point perpendicular to the touching line.

A rounded inside or outside corner produced by an arc that blends smoothly into two meeting lines, drawn by locating its centre at the radius distance from each line.

A closed curve traced by a point whose distances from two fixed foci always add to the same total, drawn by constructions such as the concentric-circle or trammel method.