Orthographic Projection Questions and Answers

Answer: C

Correct answer: two

The front view and the plan are two of the six principal views, so if between them they leave nothing undefined, two is the number required. Drawing a third would add nothing and would only create an opportunity for inconsistency, which is why the rule is the minimum that describes the object completely.

Answer: D

Correct answer: plus or minus 0.8 mm

In a chain each dimension is measured from the previous feature, so the position of the last is the sum of four independent dimensions and the worst-case tolerances add arithmetically: \[ 4 \times 0.2 = 0.8\ \text{mm}. \] This accumulation is the central drawback of chain dimensioning, and it grows with every link added.

Answer: A

Correct answer: plus or minus 0.2 mm

Measuring from a datum makes each feature’s position depend on one dimension only, so the last hole is held to the tolerance of its own dimension - plus or minus 0.2 mm - regardless of how many features lie between it and the datum. Compare the chain arrangement, where the same tolerances accumulate to plus or minus 0.8 mm.

Answer: B

Correct answer: 80 mm by 50 mm

The plan is the view from above, so it shows the two horizontal dimensions: the length of 80 mm and the width of 50 mm. Height does not appear in it at all. At a scale of 1:1 the dimensions on the sheet equal those on the object, so the plan occupies 80 mm by 50 mm.

Answer: C

Correct answer: 50 mm by 30 mm

The side elevation is the view along the length, so it shows the width and the height: 50 mm by 30 mm. Between them the three principal views show each dimension twice - length in the front view and plan, width in the plan and side elevation, height in the front and side elevations - which is what makes the views project on to one another.

Answer: D

Correct answer: transposed left for right

The two systems place the side views on opposite sides of the front view. Read a first angle drawing as third angle and the view drawn on the right, which was taken from the left, will be taken as the view from the right - so the part is made as a mirror image. The dimensions are all correct, which is what makes the error so easy to miss.

Answer: A

At 1:5 the full length would be 120 millimetres, and the break removes part of the middle so the drawn figure is shorter. The dimension written on it remains 600 millimetres, since the break is a drawing convention only.

Answer: B

Correct answer: in opposite directions or at different spacings

Hatching in the same direction and spacing across a joint would make two parts look like one. Reversing the direction, or changing the spacing where several parts meet, makes the boundary between them unmistakable. The same part must of course be hatched identically wherever it appears in the assembly.

Answer: C

Correct answer: 1-Q, 2-P, 3-R

Three line types with three distinct meanings, and the distinction is carried by both the pattern and the weight. A long chain thin line is a centre line. A thin line of short dashes is a hidden edge. A continuous thick line is a visible outline. Where two coincide the visible outline takes precedence, then the hidden edge, then the centre line.

Answer: D

Correct answer: 1-Q, 2-P, 3-R

Three sectioning devices for three different problems. A half section shows interior and exterior together on a symmetrical part. An offset section steps the cutting plane so that features not on one plane can all appear in a single view. And a revolved section rotates the cut shape through ninety degrees and draws it in place on the view.