Orthographic Projection Questions and Answers

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.

Answer: A

Correct answer: the interior and the exterior in one view

A half section cuts away one quarter of a symmetrical object, so one half of the view shows the interior in section and the other half the exterior as normal. It saves a view on a symmetrical part. By convention no hidden lines are drawn on the unsectioned half, since the sectioned half already shows what is inside.

Answer: B

Correct answer: is stepped to pass through several features

An offset section lets one view show features that do not lie on a single plane - holes at different radii, say - by stepping the cutting plane from one to the next at right angles. The steps are marked on the cutting plane line but no line is drawn where the plane changes direction in the section itself, since no such edge exists on the object.

Answer: C

Correct answer: superimposed on the view at the point of the cut

A revolved section shows the cross-sectional shape of a rib, arm or spoke by rotating the cut through ninety degrees and drawing it directly on the view at that station, outlined in a thin line. It is compact and unambiguous about where the section is taken. Drawing it elsewhere on the sheet makes it a removed section instead.

Answer: D

Correct answer: thin lines at 45 degrees, evenly spaced

Hatching is drawn thin so it does not compete with the outline, at 45 degrees to the principal outline, and evenly spaced with the spacing chosen to suit the size of the area. Where 45 degrees would run parallel to an outline, another angle is used. Adjacent parts in an assembly are hatched in opposite directions or at different spacings so the joint is visible.

Answer: A

Correct answer: shown unsectioned even when the plane passes through them

Sectioning a solid shaft, bolt, nut, key, rivet or web would show a solid area of hatching that conveys nothing, and in the case of a web would falsely suggest a solid flange. The convention is to draw such parts unsectioned even when the cutting plane passes along them, so the drawing shows the shape rather than the cut.

Answer: B

Correct answer: outside the outline of the view wherever possible

Dimensions placed outside the outline keep the view itself clear and avoid extension lines crossing the drawing. They are arranged so that the shorter dimensions lie nearest the view and the longer ones outside them, so that extension lines do not cross dimension lines. Dimensioning inside the outline is done only where clarity actually demands it.