Drawing Terminology Review

Identify the view before interpreting the shape

This short vocabulary review supports CAD certification preparation. It is general drawing language, not a list of guaranteed exam terms.

A view is a picture of the part from a chosen direction. First identify how the picture represents the part; then read its lines, dimensions, and notes.

Orthographic view: The principal orthographic views look straight at the part from the front, above, or a side, using parallel lines of sight perpendicular to each viewing plane. Front shows width and height; top shows width and depth; a side view shows depth and height. Read the views together to understand one three-dimensional part.

One stepped block beside its labeled front, top, and right orthographic views. The front has an L-shaped outline; top and right show its depth. — The pictorial on the left helps you recognize the block. The front, top, and right views on the right show the same fixed part from separate directions. This example uses third-angle placement; Orthographic Projection explains the views and First-Angle and Third-Angle Projection explains their placement on the sheet.

Isometric view: An angled pictorial that helps you see width, height, and depth together. Its three principal axis directions are 120° apart and use the same scale. An isometric projection foreshortens lengths equally along all three axes; an ordinary isometric drawing lays out axis-parallel lengths at the chosen drawing scale. Use stated dimensions to model the part rather than measuring its apparent lengths on the picture.

Three isometric axis rays labeled height, depth, and width, with 120 degrees between each pair. Below, a rectangular block has vertical edges and two sets of sloping edges following those same axis directions. — The block is an isometric drawing: its edges follow three consistent directions. The dashed grid on its top is a construction aid, not hidden edges of this part. See Pictorial Sketching for making the sketch and the distinction between drawing and projection scales; compare isometric with dimetric and trimetric in CAD Model Views and Checks.

Line conventions describe edges and centers within a view

A view type tells you how the part is represented. A line convention tells you what a particular mark means within that view. Visible, hidden, and center lines are line conventions, not additional view types.

Visible line: A continuous line shows an edge or outline you can see from this viewing direction.
Hidden line: Short dashes show an edge concealed by material.
Center line: A long-short pattern identifies an axis, center, or symmetry reference. It is not a physical seam in the part.

Labeled samples show a thick solid visible line, short-dashed hidden line, long-short center line, and long-short-short phantom line. — The first three samples match the terms above. The fourth, phantom, can indicate an alternate position or reference. Read the pattern together with its context; the dashed construction grid in the isometric figure above is a teaching aid. Review the full conventions in The Alphabet of Lines.

Read dimensions and callouts as instructions about features; Practice

Read dimensions and callouts as instructions about features

Dimension and extension lines: A dimension gives a size or location. A dimension line is a thin line, usually ending in arrowheads, that shows the extent of the measurement; extension lines carry the edges of the measured feature out to it. Read the value and units instead of measuring a picture. See Dimension Anatomy and Placement.
Diameter and radius: Diameter spans a circle through its center; radius runs from its center to its edge. The diameter symbol is Ø; R denotes radius. Confusing them changes the modeled size. See how holes and arcs are called out in Hole and Feature Callouts.
Hole and feature callout: A note describing a feature, possibly including quantity, size, depth, or thread information. A through hole passes through the material; a blind hole stops within it. See Hole and Feature Callouts.
Tolerance: The permitted variation in a specified dimension. Read the stated limits or applicable drawing note; do not assume that every dimension has the same tolerance. See Dimension Anatomy and Placement.

Practise radius and diameter

Distinguish a section, a detail, and an auxiliary view; Practice

Distinguish a section, a detail, and an auxiliary view

Section view: shows the part as if cut by an imaginary plane so internal features can be read. A cutting-plane indication locates the cut; section lining identifies material crossed by it. See Section Views.
Detail view: enlarges a selected area so small features are easier to read. Check its scale and labels.
Auxiliary view: looks perpendicular to an inclined surface to show its true shape. Compare it with a detail view in Auxiliary and Detail Views.

Before modeling, point to the view or callout that establishes each feature. If a shape is unclear, look for another view rather than guessing from a pictorial.

Check the purpose of a detail view