Active learning ideas
Washers, Rivets, and Riveted Joints cover permanent and semi-permanent fastening methods. Students learn to draw plain washers, which distribute load, and various rivet heads like snap, pan, and countersunk. The unit also introduces lap and butt joints, which are critical for structural engineering and shipbuilding. This topic emphasizes the importance of proportions in ensuring structural integrity.
Activity 01
Students use strips of cardboard and brass fasteners (acting as rivets) to create a single-riveted lap joint and a butt joint. They observe which joint is more stable and discuss why 'straps' are needed for butt joints.
What is the purpose of a washer in an assembly?
Activity 02
Students draw four different rivet heads (Snap, Pan, Mushroom, Countersunk) based on a common shank diameter. Peers walk around to check if the head heights and widths follow the standard proportions (e.g., 1.6d for snap head).
How are snap head and pan head rivets drawn?
Activity 03
Students are asked: 'Why do we put a washer under a nut on a wooden surface but sometimes skip it on a steel surface?' After discussion, they share findings about surface area and pressure distribution.
What are the proportions for a lap joint?
A few notes on teaching this unit
Watch Out for These Misconceptions
Thinking that a rivet fills the hole completely in a drawing.
In technical drawings, we show the nominal diameter of the rivet. However, students should be taught that in practice, the rivet expands. Peer discussion about the 'clearance' between the hole and the rivet helps clarify why we draw them the way we do.
Confusing 'Chain Riveting' with 'Zig-Zag Riveting'.
Students often draw rivets in straight rows when zig-zag is requested. Using a grid-paper exercise where they must place 'dots' (rivets) according to specific pitch and back-pitch rules helps them visualize the staggered pattern.
Methods used in this brief
Standard Profiles of Screw Threads
Drafting standard thread profiles such as BSW, Metric, and Square threads to scale.
8 methodologies
Nuts and Bolts
Orthographic projection of hexagonal and square nuts and bolts.
8 methodologies
Keys and Cotters
Understanding and drawing various types of keys and cotters used in shaft connections.
8 methodologies