Isometric Projection Questions and Answers

Answer: C

The number of equal inclinations decides how many separate scales the drawing needs, which is one for isometric, two for dimetric and three for trimetric. It is the reason isometric dominates practice despite the other two giving a more natural appearance.

Answer: D

Isometric treats all three directions alike, while both oblique forms privilege the front face and differ only in the depth ratio. Choosing between them is a matter of which face carries the detail and how natural the result must look.

Answer: A

The overall sizes come from the given views, the box is drawn to those sizes on the axes, the features are located by isometric offsets within it, and the outline is completed last. Each step supplies what the next one needs.

Answer: B

Correct answer: 1 and 3 only are correct

Statements 1 and 3 are correct: the three isometric axes are 120 degrees apart on the paper, and a circle lying in an isometric plane projects as an ellipse. Statement 2 is the important error - a non-isometric line is not parallel to any axis, so its drawn length is not its true length and it cannot be measured off. Such lines are located by their end points, which do lie on isometric lines.

Answer: C

Correct answer: the outline of a sphere

A sphere looks the same from every direction, so its outline is a circle of the true radius whatever the projection - it is the one shape the isometric ratio leaves alone. Every isometric edge, every box dimension and the axes of every ellipse are all scaled by it in a true projection.

Answer: D

Correct answer: it reproduces the object's absolute size correctly

That is exactly what the isometric drawing gives up. By using true lengths along the axes it comes out about 1.22 times larger than the object would actually project, so absolute size is wrong even though every proportion is right. The three genuine advantages are the ones listed: no special scale, quicker setting out, and identical shape and proportions.

Answer: A

Correct answer: appear tilted out of the face it should lie in

The ellipse representing a circle in an isometric face has its major axis along the *long* diagonal of the enclosing rhombus, perpendicular to the third isometric axis. Putting it on the short diagonal turns the ellipse through 90 degrees, and the result reads as a circle lying in a different plane - a mistake that is obvious at a glance once the rule is known and easy to make when it is not.

Answer: B

Angles open or close according to the plane they lie in, so no protractor setting corresponds to the true angle. The chamfer must be located by isometric offsets to the ends of its edges and the line drawn between them.

Answer: C

Using unreduced lengths inflates every dimension by the reciprocal of 0.816, which is about 22.5 per cent. Since the inflation is uniform the shape is unaffected, which is why the drawing is acceptable for most purposes.

Answer: D

Foreshortening is uniform only along the three isometric directions, and a line oblique to all of them shortens by a different amount. Such a line must be located from the ends of isometric measurements rather than scaled.