Technical Drawing & CAD

Technical drawing is learned by drawing, not by reading. This page holds three view-derivation exercises of increasing difficulty. The right way to work: look at … Read more

A large share of the parts that reach a machine shop are weldments: machine frames, bases, fixtures, flanged pipes. Their drawings do not show every … Read more

ISO A series drawing sheet sizes, frame and margin rules, the title block and how scale works — with original diagrams.

The eight ISO 128 line types, when to use each, the thick/thin width rule, the priority order when lines coincide, and ISO 3098 lettering.

Line-to-arc and arc-to-arc tangency, bisecting angles, dropping perpendiculars, hexagon and pentagon construction and the two circle ellipse method.

The six principal views, how to choose the front view, deriving views from a part, and the difference between first angle and third angle projection.

Full, half, local and offset sections; how the cutting plane is shown; hatching angle and spacing rules; and the parts that are never hatched.

The four elements of dimensioning, general rules, parallel/chain/running systems, feature symbols and why chain dimensioning accumulates tolerance.

What Ra means, the three basic surface texture symbols and their information fields, and which production method reaches which Ra range.

Basic size, deviations and tolerance zones; what H7 and h6 mean; clearance, transition and interference fits; hole basis versus shaft basis.