Riveted joint sizing: according to Unwin’s formula, how are rivet-hole diameter (d, mm) and plate thickness (t, mm) related?

Introduction / Context:
Riveted joint design historically relied on empirical rules to choose rivet-hole diameters compatible with plate thickness, manufacturing, and structural integrity. Unwin’s formula is a widely cited relation that provides a quick estimate for preliminary design.

Given Data / Assumptions:

• Plate thickness t in millimetres.
• Rivet-hole diameter d to be sized for general structural use.
• Standard ductile plate materials and fabrication methods.

Concept / Approach:
Unwin’s rule of thumb relates hole diameter linearly to plate thickness, ensuring adequate shear area of the rivet, acceptable bearing stresses in the plate, and practical hole manufacture. For many common ranges of t, d is taken as roughly 1.5 t, with variants (e.g., 1.75 t) used for thicker plates or different materials.

Step-by-Step Solution:

Verification / Alternative check:
Design texts show families of empirical relations; d = 1.5 t is a standard value within common thickness ranges and matches drill/punch practicality.

Why Other Options Are Wrong:

• 1.1 t: too small, risks tearing/bearing issues.
• 1.6 t: possible variant but not the classic Unwin value given in many sources.
• 3 t: unrealistically large, poor material utilization.

Common Pitfalls:
Using a single factor outside its applicable thickness/material range; not checking edge distances or pitch that also govern joint efficiency.

Final Answer:
d = 1.5 t