Module 7.8 and 7.14 Riveting and material handling (sheet metal, composites, additive manufacturing)

Knowledge levels

Item	A	B1 / B3	B2 / B2L
7.8 Riveting: joints, spacing and pitch, tools, dimpling, inspection	1	2	—
7.14.1 Sheet metal: marking out, bend allowance, bending and forming, inspection	—	2	—
7.14.2 Composite and non-metallic: bonding practices, environmental conditions, inspection	—	2	—
7.14.3 Additive manufacturing	1	1	1

B2/B2L are examined only on 7.14.3 in this note.

7.8 Riveted joints

• Rivets carry loads mainly in shear; joints are designed so the rivet and the sheet fail at similar loads.
• Rivet diameter: typically about 3 × the thickness of the thickest sheet (rounded to the next standard size).
• Edge distance (centre of rivet to edge of sheet): minimum 2 D (2 × diameter) for protruding heads, usually 2-2.5 D (2.5 D for countersunk heads).
• Rivet pitch (centre-to-centre in a row): minimum 3 D, typically 4-6 D, maximum usually 10-24 D depending on the structure.
• Transverse pitch (row spacing): about 75 % of the rivet pitch; rows staggered.
• Grip = total thickness of material; rivet length = grip + about 1.5 D for forming the shop head.
• Shop head dimensions (driven head): diameter about 1.5 D, height about 0.5 D.

Key fact: Rivet diameter ≈ 3 × thickest sheet; edge distance ≥ 2 D; pitch ≥ 3 D; length = grip + 1.5 D.

Worked example

Join two sheets of 1.0 mm and 1.2 mm.

• Diameter ≈ 3 × 1.2 = 3.6 mm → choose the next standard size, e.g. 4 mm (5/32 in ≈ 3.97 mm)
• Edge distance ≥ 2 × 4 = 8 mm; minimum pitch ≥ 3 × 4 = 12 mm
• Grip = 2.2 mm; length ≈ 2.2 + 1.5 × 4 = 8.2 mm (choose the nearest standard length above)

Riveting tools

• Drills (sized to give the correct hole clearance, e.g. #30 for 1/8 in rivets, #40 for 3/32 in), deburring tools, clecos (temporary sheet fasteners) to hold sheets in place.
• Rivet gun (pneumatic, with correct set for the head shape) and bucking bar (weight and shape matched to the rivet size). Hand squeezers for accessible edges.
• Countersinking: cutting a conical recess (100°) in sheets thick enough (sheet thicker than the rivet head height). Dimpling: pressing the sheet into a cone shape for thin sheets (too thin to countersink) - cold dimpling for soft alloys, hot dimpling for 7075 and magnesium (prevents cracking).
• Rivet removal: drill through the manufactured head with a drill one size smaller than the shank, break the head off with a pin punch, punch out the shank - avoid enlarging the hole.