Supplied B1 Module 07A textbook: PDF pages 205–224.
Joint load paths and rivet choice
A riveted joint transfers load through fastener shear and sheet bearing. Joint design also controls fatigue, sealing and local stress. Match the specified rivet material, diameter, head type and length; a visually similar fastener may have different strength or installation requirements. Solid rivets need access for a driven shop head, while approved blind rivets permit restricted-access installation. Blind rivet types are not universally interchangeable. The structural repair drawing governs the selection, pattern and permitted substitution.
What governs rivet selection in a structural repair? The approved repair specification.
Pitch, gauge and edge distance
Pitch is the centre-to-centre distance of rivets along a row. Row spacing, sometimes called gauge, separates adjacent rows. Edge distance is measured from the rivet centre to the sheet edge. Too little edge distance can tear the sheet; unsuitable spacing can affect load sharing and fatigue. Common training rules such as a minimum pitch of about 3D or edge distances around 2D to 2.5D are typical guidance, not universal authorisation. Always use the drawing's limits for head type, material and joint configuration.
How is rivet edge distance measured? From rivet centre to the sheet edge.
Hole preparation and temporary fastening
Align and clamp sheets, then drill the prescribed holes without introducing burrs or distortion. Cleco temporary fasteners hold the assembly; they are not permanent structural fasteners. Use correct hole size and remove debris from between sheets. An oval, oversized or mislocated hole changes the joint's load path. Deburr carefully so the hole edge is smooth without an excessive chamfer. Inspect the assembly before installing permanent fasteners, especially where later access will be limited.
What is the purpose of a Cleco fastener? Temporary alignment and holding during assembly.
Countersinking and dimpling
Countersinking removes material to receive a flush head. Dimpling forms the sheet into a conical recess instead of cutting away the full recess. Thin sheet may need dimpling because a deep countersink can create a knife edge and reduce support. Match dies, head angle and nested-sheet configuration. Check for cracked dimples, excessive depth or a proud head. A flush appearance alone does not establish acceptable remaining sheet thickness or joint integrity.
Why is dimpling often used in thin sheet? It forms a recess without removing as much material.
Driving and squeezing solid rivets
Support the manufactured head with the correct set and form the shop head with a bucking bar or squeeze tooling. Keep the tooling aligned and support the work to avoid dents. Typical training dimensions for a formed shop head are approximately 1.5D in diameter and 0.5D high; the actual acceptance criteria govern. Rivet length must include grip and the allowance needed to form the head. Overdriving, underdriving and tilted tooling can damage the joint. Use correct eye and hearing protection.
What does rivet grip refer to? The thickness of material being joined.
Joint inspection and rivet removal
Inspect head seating, shop-head shape, cracks, sheet separation and surrounding dents. Look for loose rivets, movement marks and fretting. Blind fasteners need checks appropriate to stem retention and locking design. To remove a rivet, use the approved method that separates the head without enlarging the hole or damaging the sheet. Support the work when driving out the remaining shank. If a hole is damaged, assess it against approved repair data rather than automatically installing a larger fastener.
Why must rivet removal avoid enlarging the hole? The original joint limits and load transfer may be lost.
Apply the knowledge
Work through these examples before starting the quiz. Explain why the other choices would not meet the requirement.
A 4 mm rivet uses a typical 3D pitch guideline. What pitch does that give?
12 mm — 3 × 4 = 12 mm; the approved drawing still governs.
Using typical 1.5D by 0.5D shop-head guidance for a 4 mm rivet, what dimensions result?
6 mm diameter and 2 mm height — Multiply the shank diameter by the stated proportions.
A thin sheet would become knife-edged if countersunk. Which approach may be specified?
Dimpling with the approved tooling — Dimpling forms the sheet rather than cutting the entire recess.
Dark fretting marks appear around a rivet. What do they suggest?
Possible relative movement requiring assessment — Fretting can indicate movement at the joint.