Advanced geometric pattern development · Lesson 1 of 4

Advanced geometric pattern development: principles and terminology

Why a pattern comes first, the four layout methods and what each one is used for, which surfaces unfold exactly, the words a pattern drawing uses, how true length is found, and the hazards of cut edges.

You will be able to: Name the four layout methods and the fittings each one suits, tell developable from non-developable surfaces, define element, stretch-out, apex, slant height, true length and allowance, and state the safety boundaries.

10 min · 10 slides · 7 questions

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Slide 1 of 10

Why the pattern comes first

The Red Seal standard (Canada) calls pattern development the starting point of fabrication.

A worker develops a pattern by hand or by computer, using one or more of four layout methods, and must know which method to use.

A development opens a rolled or folded object out flat so it can be cut from sheet and formed; the US Navy lists flashing, valleys and downspouts among its uses.

Sources

Red Seal Occupational Standard, Sheet Metal Worker (2026), Task B-6 Performs pattern development - Employment and Social Development Canada (Red Seal Program)
Blueprint Reading and Sketching, NAVEDTRA 14040 (May 1994), Chapter 8 Developments and Intersections - U.S. Navy, Naval Education and Training Professional Development and Technology Center

Glossary

Pattern development: Laying out a flat pattern from a drawing so that an object can be cut from flat sheet and rolled or folded into shape.
Developable surface: A surface a thin flexible sheet can wrap smoothly, such as a prism, cylinder or cone; double-curved and warped surfaces are not developable.
Element: In pattern development, one of the evenly spaced reference lines drawn on the surface of the object and carried onto the pattern.
Stretch-out: The base line of a pattern: the perimeter of the object unrolled flat. For a cylinder it equals the circumference.
Slant height: The distance from the apex of a cone to its base measured on the cone surface; it is the radius used to swing a cone pattern.
True length: The real length of a line. A line shows its true length only when viewed at right angles to it; otherwise it is found as the hypotenuse of its plan length and its height.
Allowance: Extra metal added to a pattern outside the developed outline for seams, joints and edges.