Materials and Hardware
What the module tests
Materials and hardware covers ferrous and non-ferrous metals, composites, corrosion, fasteners, pipes, springs, bearings, transmissions, control cables and electrical cables. Questions test selection, identification and correct installation rather than metallurgy for its own sake.
Core rules
- Aluminium alloys need protective finishes; bare aluminium and steel together promote galvanic corrosion.
- Rivet length = grip length + about 1.5 × diameter for a universal-head rivet.
- Grip length is the total thickness of the material being joined, not the rivet length.
- Threads: AN and MS hardware identification matters; a fine-thread bolt is not interchangeable with a coarse-thread one.
- Bearings need the correct fit and lubrication; preload and clearance are specified, not guessed.
- Control cables must be rigged to specified tension and inspected for broken strands, corrosion and fairlead wear.
Worked example
Two sheets of 1.6 mm and 1.2 mm are joined with a 4 mm diameter universal-head rivet. Find the grip and the nominal rivet length. Grip = 1.6 + 1.2 = 2.8 mm. Rivet length = grip + 1.5D = 2.8 + (1.5 × 4) = 2.8 + 6.0 = 8.8 mm. Select the next standard length, 9 mm, and confirm the installed shop head meets the diameter and height limits.
Traps
Confusing grip with overall rivet length; using the wrong head allowance; mixing AN and MS part numbers; ignoring dissimilar-metal separation; over-torquing composite fasteners; assuming a bearing is serviceable because it rotates freely.
Exam approach
Identify the material pair and the fastener standard first. For rivets, always calculate grip before length. For corrosion questions, name the type and the driving condition.