Rivet Size Calculator (solid rivet diameter, length, edge distance and pitch)

Understanding the rivet size calculator — concept and principle

This calculator suggests the diameter and length of a solid shank rivet for joining sheet metal, and the minimum edge distance, rivet pitch and row spacing, using rules of thumb from aircraft-style sheet-metal practice. Builders of light structures, kit aircraft and students of sheet-metal work use it.

How it is calculated

Diameter ≈ 3 × thickness of the thicker sheet, rounded up to the next 1/32 inch (dash number = diameter in 32nds)

Length = grip + 1.5 D, rounded up to the next 1/16 inch

Edge distance: minimum 2 D, recommended 2.5 D

Rivet pitch: minimum 3 D, typically 4–6 D; transverse pitch: minimum 2.5 D

• Thickness and grip (total of all sheets) in mm; results in inches and mm.

The principle

A rivet must be strong enough in shear for the load the sheets carry, which ties its diameter to the sheet thickness. It must also be long enough to fill the hole and leave material to form the shop head, about 1.5 diameters beyond the grip. Holes too close to the edge tear out, and holes too close together weaken the sheet between them, so edge distance and pitch are set in multiples of the diameter.

Worked example

Default inputs: thicker sheet 1.0 mm, grip 2.0 mm.

1. Minimum diameter = 3 × 1.0 = 3 mm; next standard size is 4/32 = 1/8 in (−4) = 3.17 mm.
2. Length = 2.0 + 1.5 × 3.175 = 6.76 mm, rounded up to 5/16 in (−5).
3. Edge distance: minimum 6.3 mm, recommended 7.9 mm.
4. Pitch: minimum 9.5 mm, typical 12.7–19 mm; transverse pitch minimum 7.9 mm.

How to read the result

These are planning values. In certified aircraft, the drawing or structural repair manual sets rivet type, size and spacing, and it overrides any rule of thumb. Countersunk rivets often need a larger edge distance.

Common mistakes

• Using the thinner sheet to size the rivet.
• Measuring grip on one sheet only instead of the whole stack.
• Placing rivets closer than the minimum edge distance.

Frequently asked questions

What does −4 mean?

The dash number gives the diameter in 32nds of an inch, so −4 is 4/32 = 1/8 in.

Why add 1.5 D to the grip?

That extra shank forms the shop head when the rivet is driven.

What is grip?

The total thickness of all the sheets the rivet passes through.

Why space rivets 4–6 D apart?

Closer spacing weakens the sheet; wider spacing lets the sheets separate between rivets.

Sources: Aero Guide (aircraftsystemstech.com), "Solid Shank Rivet — Aircraft Structural Fasteners" (2018), summarising FAA aviation-maintenance training material