A sectional view shows the cut face hatched, with the outline of the solid around it. You build it from the outside in, then subtract anything that is empty.
This lesson follows interpreting a stated cutting plane and belongs to sections and spatial reasoning.
What is the drawing routine?
Use four steps.
- Draw the outline of the solid as the plane cuts it.
- Mark the empty spaces, such as holes or cavities.
- Hatch only the remaining cut material.
- Add any visible edges lying beyond the plane.
Worked example: a plate with a drilled boss
An original solid has a rectangular plate 60 mm wide, 40 mm deep and 10 mm high. A cylindrical boss of diameter 20 mm and height 15 mm stands at its centre, so the total height is 25 mm. A blind hole of diameter 10 mm and depth 12 mm is drilled down from the top of the boss, on the centre line. Plane A-A passes through the centre, viewed from the front.
Step 1. The outline is the plate, 60 × 10, with the boss above it, 20 wide and 15 high. The solid stands 25 mm tall.
Step 2. The hole is 10 mm wide and runs from the top at 25 mm down to 25 − 12 = 13 mm. It is empty.
Step 3. Hatch the rest. On each side of the hole, the boss wall is (20 − 10) ÷ 2 = 5 mm wide. Below the hole there is a floor 13 − 10 = 3 mm thick joining the boss to the plate.
Step 4. Nothing else lies beyond the plane in this symmetrical example, so the drawing is complete.
The hatched region is one continuous shape: a wide base 60 mm by 10 mm, a boss above it 20 mm wide, and a hole cut into the boss from the top.
The mistake: a line between plate and boss
The plate and the boss are cut from the same piece of material. Drawing a horizontal line at height 10 mm across the cut face implies they are separate parts.
| Step | Wrong | Right |
|---|---|---|
| Joint between plate and boss | Line drawn at 10 mm | No line, one hatched region |
| The 3 mm floor | Left out | Hatched, joining boss to plate |
| Hole sides | Stop at 10 mm | Stop at 13 mm, the hole bottom |
The test for any line is whether it is an edge of the solid in this view. The plate top beside the boss is an edge. The junction inside the boss is not.
Hatching rules in one place
Keep the angle and the spacing the same across the whole cut face, including the floor. Stop every line at the outline or at the hole edge. Never hatch over the dimension text.
Check yourself
A rectangular block is 50 mm wide and 30 mm high, with a central rectangular slot 20 mm wide running through its full height. Plane A-A cuts across the width. Give the hatched widths.
Answer
The slot is empty, so the plane cuts two solid strips, one on each side. Each has width (50 − 20) ÷ 2 = 15 mm and height 30 mm.
Draw the slot’s two sides as visible vertical lines. Do not hatch the 20 mm gap.
What to study next
Continue with explaining which internal features a section reveals, then test yourself in the sections practice set.
If you want a teacher to watch your drawing sequence on a fresh solid, see online one-to-one Engineering Drawing tuition.