Three views are consistent when they all show the same solid. To check, compare the measurements that each pair of views shares.
This lesson is part of SPM subjects and learning resources. It follows on from reading spatial information from views, and it leads into reviewing dimensions and consistency in your own drawing.
The three alignment rules
Each measurement appears in two different views. Check the rules in this order.
- Width: the front view and the top view must be the same width.
- Height: the front view and the side view must be the same height.
- Depth: the top view’s depth must equal the side view’s width.
The third rule catches students out. The same measurement is the depth in the top view, but it is the width in the side view. Both are the distance from front to back of the solid.
Worked example: a consistent set and a faulty set
An original stepped block has these views, in millimetres.
| View | Outline | Internal line |
|---|---|---|
| Front | 70 wide, 40 high | Horizontal line 15 from the bottom |
| Top | 70 wide, 35 deep | Line 15 from the front edge |
| Side | 35 wide, 40 high | Step: the front 15 of the depth is 15 high |
Rule 1. Front width 70, top width 70. Matches.
Rule 2. Front height 40, side height 40. Matches.
Rule 3. Top depth 35, side width 35. Matches.
Feature check. The front line at 15 high, the top line 15 from the front and the side step of 15 by 15 all describe the same low step at the front. This set is consistent.
Now change one thing. Suppose a student’s top view is 65 wide and 35 deep, with the front and side views unchanged. Rule 1 fails, because the front says 70 and the top says 65. Both cannot be right, so the student goes back to the original drawing or model and decides which measurement is correct.
The missing-line test
Consistent views also agree on features. When a feature shows in one view, ask where it should appear in the other two.
For example, a step visible in the side view must also produce a line in the front view and a line in the top view. A vertical hole seen as a circle in the top view appears in the front view as two hidden (dashed) lines, because it is inside the solid. If a line has no partner, either a feature is missing or the line should not be there.
The mistake that costs marks
Many students check only the outline sizes and forget the internal lines. The outlines match, so they stop, but a step is drawn in only one view.
Do both checks every time. Apply the three outline rules first, then go through every internal line and ask where its partners are. Tick each line that has them.
Check yourself
A set has these views. Front: 50 wide, 30 high, with a dashed rectangle 10 wide.
Top: 50 wide, 25 deep, with a circle of diameter 10. Side: 30 wide, 30 high. Find the error.
Answer
Rule 1: front width 50, top width 50. Matches.
Rule 2: front height 30, side height 30. Matches.
Rule 3: top depth 25, but the side width is 30. They should be equal, so this is the error. Either the top view’s depth is wrong, or the side view’s width is wrong.
The dashed rectangle 10 wide in the front view agrees with the circle of diameter 10 in the top view, because a vertical hole is a circle from above and dashed lines from the front. So the hole is consistent, and the faulty measurement is the depth.
What to study next
Move on to reviewing dimension and view consistency in your own drawing, then test the whole set with the original practice questions.
If you want a teacher to go through your views line by line with you, see online one-to-one Technical Communication Graphics tuition.