In an oblique drawing, the front face is shown in true shape and the depth is drawn as sloping lines. You can read the front lengths directly, but the depth lines need converting, and the rule depends on whether the style is cavalier or cabinet.
This lesson is part of pictorial representations. It follows telling isometric from perspective views.
How do the two oblique styles differ?
| Style | Front face | Receding edges | Real depth from drawn |
|---|---|---|---|
| Cavalier | True shape | Full length, commonly at 45° | Same as drawn |
| Cabinet | True shape | Half length, commonly at 45° | Drawn × 2 |
The angle is a convention, and 45° is a common choice. Read the angle and the style from the question, not from memory.
Worked example: one block, two styles
An original block is 60 mm wide, 40 mm high and 30 mm deep.
Cavalier. Draw the front face as a 60 × 40 rectangle. From each corner, draw receding lines at 45°, each 30 mm long. Join their ends to complete the back face.
Cabinet. Draw the same 60 × 40 front face. The receding lines are at 45°, each 15 mm long (half of 30). The back face is the same size as the front, shifted by the receding lines.
Both drawings show a 30 mm deep block, but the cabinet one looks less stretched.
How do you convert back to real depth?
Reverse the rule. Take a drawing you are given.
A cabinet oblique drawing shows a front face 50 × 35 and receding edges drawn 12 mm long. Real depth = 12 × 2 = 24 mm.
In a cavalier drawing, the same 12 mm receding line means a depth of 12 mm. The drawn length is identical, but the real depth differs, which is why the style matters.
The mistake: reading drawn depth as real depth
A student sees a cabinet drawing with receding edges of 20 mm and concludes that the object is 20 mm deep. The front face is right, so the student trusts the whole drawing.
| Step | Wrong | Right |
|---|---|---|
| Identify the style | Not checked | Cabinet, stated in the note |
| Receding edge | Take as real depth | Double it |
| Real depth | 20 mm | 40 mm |
| Sense check | A block that looks shallow | A block 40 mm deep |
A second slip is to draw a circle on the front face as an ellipse. That face is true shape, so the circle stays a circle. Only circles on the receding faces are distorted.
Check yourself
A cabinet oblique drawing shows a front face 80 mm wide and 50 mm high, with receding edges drawn 18 mm long. A cavalier drawing of a different block shows receding edges also drawn 18 mm long. Find the real depth of each block.
Answer
Cabinet: real depth = 18 × 2 = 36 mm. Cavalier: real depth = 18 mm, because full length is used. The same drawn length gives different depths, so the style must be read first.
What to study next
Test yourself on all pictorial styles with the pictorial representations practice set.
If you want a teacher to give you oblique drawings in both styles and check your conversions, see online one-to-one Engineering Drawing tuition.