Parallel Line Pattern Development


When wanting to build a project, we need to first imagine it. The process of pattern development gives us the ability to take that visual representation and actually create the object. It allows us to turn two-dimensional metal into three-dimensional objects, which is the basis for everything we fabricate.

Consider a globe and a map. The map is a 2D representation of a 3D object. What should the map look like? Is it truly flat? Well, maybe some would argue, but a map is not a true representation of the Earth until we remove some of it. The actual shape of the map will have numerous “cut outs” which would allow it to form a sphere. This is a form of pattern development.

Learning Objectives

  1. Understand the parallel line pattern development processes.
  2. Understand the “language” of layout.

Layout Terms

  1. Allowance – the material needed for a specific component. “We must allow this much extra.” Usually a seam for connection.
  2. Auxiliary Line – an extra element line added, different from the standard divisions.
  3. Elbow Rule – the number of pieces of a round elbow times 2 then minus 2 (# of pcs × 2 − 2) gives us the number of gores in the elbow.
  4. Element Line – a line representing an edge or bend.
  5. Elevation View – looking at the front or side of something, to have elevation (height), 2D.
  6. Gore – a part of a round elbow which allows us to calculate the miter angle.
  7. Miter – an intersection of 2 pieces, an irregular cut on the end of something.
  8. Pattern – the shape of the object, still in 2D form.
  9. Plan view – looking down at something, a “birds eye view,” “floor plan,” (2D).
  10. Profile – a half of a plan view, drawn on the outside of an object.
  11. Sector – a special profile which is inside of an object, a section view.
  12. Stretch-out -a shape which has been “stretched out,” to take a perimeter and make it straight.

Parallel Line Development

The process of pattern development is the way we turn 2D sheets of metal into 3D objects. A parallel line is one of the basic forms of layout. We use it when element lines (bends) on an object are indeed parallel. The two ends of the part must be the same. Consider a gutter: It may have curves and bends and angles, but each end is the same shape. The element lines and bends are all parallel. This is the only factor which will allow parallel line pattern development to be used.

Basic Steps

  1. Draw a full plan and elevation view, complete with all element lines and miter lines.
  2. Draw a stretch-out, complete with all element including auxiliary lines.
  3. Transfer the lengths (height) of the element lines from the elevation view to the corresponding element line on the stretch-out.
  4. Join the point to create the pattern.


Icon for the Creative Commons Attribution 4.0 International License

Pattern Development: Sheet Metal Level 1 Copyright © 2021 by Brian Coey is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

Share This Book