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A truncated cone shown in two views, stating which projection convention a drawing uses.
Also known as: European projection symbol, Cone symbol on a drawing
This symbol exists because two incompatible conventions are in use: first-angle in Europe, third-angle in North America. A drawing read under the wrong one has its views on the wrong sides, and the parts come out mirrored.
States that the drawing's views are arranged by first-angle projection, in which each view is placed on the side away from the observer.
Contexts: Technical drawing
Exists because first-angle and third-angle projection are both in wide use and produce arrangements that are mirror images of each other, so a drawing without the symbol is genuinely ambiguous.
Contexts: Technical drawing
Is governed by ISO 128, which sets out the presentation conventions of technical drawings.
Contexts: Technical drawing
A truncated cone drawn in side view as a trapezoid, beside its end view drawn as two concentric circles, with the circles placed to the left of the trapezoid.
The symbols are mirror images and are read at a glance, which is exactly when a mirror image is missed.
The two conventions arrange views on opposite sides; the symbols are mirror images.