Orthographic Projection Questions and Answers

Answer: C

Correct answer: shows the most characteristic shape with fewest hidden lines

The front view sets the arrangement of everything else, so it should be the one that conveys most at a glance: the outline that identifies the object, in the position it occupies in use or manufacture, with as few hidden edges as possible. Area on the sheet and proportion are irrelevant, and choosing the view with most hidden lines is the opposite of the rule.

Answer: D

Correct answer: six

An object can be viewed along each of three mutually perpendicular axes from either end, giving six principal views: front, rear, left, right, top and bottom. An auxiliary view, taken normal to an inclined face, is not among them. In practice most objects need two or three, and the rest are drawn only if they add something.

Answer: A

A face oblique to all three principal planes appears foreshortened in every principal view, so a plane parallel to it is introduced. The projector direction is perpendicular to that inclined face rather than to a principal plane.

Answer: B

Correct answer: the minimum that describes the object completely

Two rules apply together: the drawing must be unambiguous, and it must not be cluttered. So the number of views is the smallest that leaves nothing undefined - often two for a simple part, three for most, more only where hidden detail or inclined faces demand them. Extra views cost drawing time and add opportunities for inconsistency.

Answer: C

Correct answer: short-dashed thin line

A hidden edge is one that exists but cannot be seen from that direction, and it is drawn as a thin line of short dashes. Keeping it thin and dashed distinguishes it at a glance from a visible outline, which is continuous and thick, and from a centre line, which is a long chain. Line type is the drawing’s vocabulary and each type means one thing.

Answer: D

Correct answer: long chain thin line

A centre line marks an axis of symmetry or the centre of a hole or shaft, and it is drawn as a thin long chain - long dashes separated by short ones. It extends a little beyond the outline so that it is unmistakable, and it should cross at a long dash rather than a gap at the centre of a circle.

Answer: A

Correct answer: the visible outline

Where two line types coincide there is an order of precedence, and the visible outline takes the highest place, followed by the hidden edge and then the centre line. The logic is that the most definite information should be shown: the reader can infer that a hidden edge lies behind a visible one, but not the reverse.

Answer: B

Correct answer: long chain line thickened at its ends and changes of direction

The cutting plane is a long chain line, thin along its length but thickened at each end and at every change of direction, with arrows at the ends showing the direction of viewing and capital letters identifying the section. The thickening marks exactly where the plane begins, ends and steps, which is what an offset section needs.

Answer: C

Correct answer: continuous thin line with freehand zigzags

A break line lets a long uniform component be drawn shortened so it fits the sheet, with the dimension stated at its full value. The freehand or zigzag form makes it unmistakably a break rather than a real edge. It may only be used where the omitted portion is uniform, so that nothing is concealed by the shortening.

Answer: D

Correct answer: entirely through the object

In a full section the cutting plane passes right through, so the whole of the view is shown in section and all the interior detail becomes visible outline rather than hidden edge. It is the clearest way of showing a complicated interior, at the cost of losing the outside appearance - which is what a half section is for.