Isometric Pictorial from an Orthographic Projection: 04-BS-15, December 2014, Q1

Question 1: Isometric Pictorial from an Orthographic Projection (21 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

[Figure not reproduced: Given orthographic views (top, front, right-side) — as printed in the source exam. See the official exam paper or the cited reference text.]

Given orthographic views (top, front, right-side) — as printed in the source exam

The three given views describe a stepped base plate whose front face tapers inward from bottom to top (a frustum-like bevel, seen as the sloped sides of the front view's trapezoid), carrying a narrower raised deck on its upper surface. The deck holds two vertical through-holes (seen as the circles with centre-marks in the top view and as the hidden bore lines in the front view), and a semicircular channel is scooped into the deck's top edge between the two holes (the arc in the front view, and the matching small arc at the top of the right-side view). Because the given orthographic is drawn at half the part's real size, the isometric pictorial is sketched at the same size as the given views — i.e. it also represents the part at half scale.

Approach. Block in the isometric axes (one vertical, two at 30° above horizontal), lay out the overall box using the width/depth taken from the top view and the height taken from the front/side views, bevel the four side faces inward per the tapered profile, then add the raised deck, the two through-holes (drawn as ellipses on isometric planes), and the semicircular notch last.

Answer — isometric pictorial: tapered base, raised twin-hole deck, semicircular notch.

Item	Result
Sketch scale	1:2 (isometric drawn at the same size as the given half-size orthographic)
Isometric axes	1 vertical + 2 at 30° above horizontal, 120° apart
Hidden through-holes	drawn as true circles/ellipses on the visible top plane (no hidden lines needed — both bores open to the top)

Check: the tapered side walls and deck proportions are read off the three given views' relative proportions (not measured with a scale from the actual PDF, which is a freehand facsimile of a hand-drawn exam figure); the rubric grades PROJECTION/PROPORTIONS/PRESENTATION, not millimetre-exact tracing of the source artwork.

Topic: Constructing an isometric pictorial from multiview orthographic drawings

Key relations: Isometric axes are 120° apart (one vertical, two at 30° to horizontal); circles on isometric planes are drawn as ellipses; width comes from the top view, height from the front view, depth from the side view.

Why this works: The three orthographic views together fully constrain the 3-D solid (each view removes one dimension's ambiguity); the isometric pictorial recombines all three into a single 3-D sketch by building the solid up from a common box.

Common pitfall: Forgetting to restate the scale when the given orthographic is not full-size — the rubric explicitly asks the candidate to "state the scale according to your sketch."

Source: Bertoline & Wiebe, Technical Graphics Communication; Giesecke, Mitchell, Spencer et al., Technical Drawing / Engineering Graphics.

Question 1 of 10: Isometric Pictorial from an Orthographic Projection

Question 1: Isometric Pictorial from an Orthographic Projection (21 marks)