Active learning ideas
Sectional views of machine blocks are essential when internal complexities make standard orthographic views cluttered with too many hidden lines. By 'cutting' the block, we can show internal holes, ribs, and slots as solid features. This topic covers full sections (cutting the whole block) and half sections (cutting only half to show both internal and external features).
Activity 01
Groups are given a drawing of a complex block with many hidden lines. They must redraw it as a sectional view and then present a comparison of which drawing is easier to read and why.
How does a full section differ from a half section?
Activity 02
Using a 3D model of a symmetrical part (like a flange), students use a 'cutting plane' to remove one quarter. They then observe how the front view now shows half internal and half external detail.
Which features of a machine block are typically not sectioned?
Activity 03
The teacher shows a sectional view of an assembly including a bolt and a rib. Students must discuss with a partner which parts should be hatched and which should be left solid according to BIS standards.
How do you represent a cutting plane line on a drawing?
A few notes on teaching this unit
Watch Out for These Misconceptions
Every part the cutting plane touches must be hatched.
Standard conventions dictate that 'thin' parts like ribs, webs, and spokes, as well as fasteners like bolts and pins, are not hatched if the cut is longitudinal. This prevents the drawing from looking 'solid' when it is actually a thin support. Peer-teaching these 'exceptions' helps reinforcement.
A half-section is used for any object.
Half-sections are primarily used for symmetrical objects. They allow the engineer to show internal and external details in a single view. Using a 'Simulation' with symmetrical vs. asymmetrical models helps students see where this technique is appropriate.
Methods used in this brief
Principles of Orthographic Projection
Detailed study of First Angle and Third Angle projection methods. Students learn the standard symbols and layout of multi-view drawings.
8 methodologies
Multi-view Projections of Simple Blocks
Converting 3D pictorial views of simple machine blocks into 2D orthographic views. Focus is on hidden lines and center lines.
8 methodologies