The calculator
Runs in your browser. Inches or millimetres at the top. Thickness is the sheet being spliced; a thickness between two rows of the table is read at the next thicker row.
How the tables work
Rivets = W × (rivets per inch) × joint factor, rounded up. W is the width of material the joint has to carry. The rivets-per-inch figure comes from the table for the sheet alloy, read at the sheet thickness and rivet size.
Each table was built the same way. The AC's engineering notes say it takes a strip of sheet 1 inch wide in tension, works out the load that strip carries, and divides it by the load one rivet can take. One rivet's load is the lower of two limits: shear of the rivet, or bearing of the sheet against the rivet. Bearing is taken as 160% of the sheet's allowable tensile stress, using nominal hole diameters.
Which limit governs shows in the table itself. In thin sheet the count is flat down a column. On Table 4-9 a 1/8" rivet needs 4.9 per inch from 0.016" to 0.025": in that zone the hole elongates in bearing before the rivet shears, and the rivet's load is tied to the same sheet thickness as the load it must carry. Below that zone the count climbs with thickness, because the rivet's shear strength stays fixed while the sheet carries more. The AC marks the boundary with an underline; the calculator finds it from where the column stops being flat.
The joint factor comes from the notes under each table: 80% for stringers in the upper surface of a wing or in a fuselage, 60% for intermediate frames, 75% for single-lap sheet joints. With no note that applies, use the full figure.
Size the rivet first. The AC's general rule (par. 4-57g(3)) is a rivet diameter of about three times the thickness of the thicker sheet. The tables leave a combination blank where the rivet is too large or too small for the sheet.
Worked example — the AC's own
AC 43.13-1B par. 4-58g: a single-lap splice in clad 2024 sheet, 0.032" thick, 10" wide.
- Rivet size: 3 × 0.032 = 0.096". The AC picks 1/8" 2117-T4 (AD), and notes 5/32" would also do.
- Table 4-10, 0.032" row, 1/8" column: 4.9 rivets per inch.
- Single-lap sheet joint, note c: 4.9 × 0.75 = 3.7 per inch.
- 10" × 3.7 = 37 rivets.
- One row of 37 across 10" would be far below 3D pitch. Two rows of 19 give a pitch of about 0.52", just over 4D.
37 rivets, in two rows of 19 — the AC's answer. Read Table 4-9 instead, which also names clad 2024-T3, and the same joint needs 6.2 × 0.75 × 10 = 47. The AC does not say which table governs clad 2024-T3; its example uses 4-10. The calculator shows both and leads with the higher figure.
AC 43.13-1B Table 4-9
Bare 2014-T6, 2024-T3, 2024-T36 and 7075-T6 sheet; the same alloys clad; 2024-T4 and 7075-T6 plate, bar, rod, tube and extrusions; 2014-T6 extrusions.
| Sheet t | 3/32 | 1/8 | 5/32 | 3/16 | 1/4 | AN-3 bolt |
|---|---|---|---|---|---|---|
| .016" | 6.5 | 4.9 | — | — | — | — |
| .020" | 6.9 | 4.9 | 3.9 | — | — | — |
| .025" | 8.6 | 4.9 | 3.9 | — | — | — |
| .032" | 11.1 | 6.2 | 3.9 | 3.3 | — | — |
| .036" | 12.5 | 7.0 | 4.5 | 3.3 | 2.4 | — |
| .040" | 13.8 | 7.7 | 5.0 | 3.5 | 2.4 | 3.3 |
| .051" | — | 9.8 | 6.4 | 4.5 | 2.5 | 3.3 |
| .064" | — | 12.3 | 8.1 | 5.6 | 3.1 | 3.3 |
| .081" | — | — | 10.2 | 7.1 | 3.9 | 3.3 |
| .091" | — | — | 11.4 | 7.9 | 4.4 | 3.3 |
| .102" | — | — | 12.8 | 8.9 | 4.9 | 3.4 |
| .128" | — | — | — | 11.2 | 6.2 | 3.2 |
Rivets per inch of width “W”, 2117-T4 (AD) protruding-head rivets. “—” means the AC gives no value for that combination.
AC 43.13-1B Table 4-10
2017, Alclad 2017 and Alclad 2024-T3 sheet, plate, bar, rod, tube and extrusions.
| Sheet t | 3/32 | 1/8 | 5/32 | 3/16 | 1/4 | AN-3 bolt |
|---|---|---|---|---|---|---|
| .016" | 6.5 | 4.9 | — | — | — | — |
| .020" | 6.5 | 4.9 | 3.9 | — | — | — |
| .025" | 6.9 | 4.9 | 3.9 | — | — | — |
| .032" | 8.9 | 4.9 | 3.9 | 3.3 | — | — |
| .036" | 10.0 | 5.6 | 3.9 | 3.3 | 2.4 | — |
| .040" | 11.1 | 6.2 | 4.0 | 3.3 | 2.4 | — |
| .051" | — | 7.9 | 5.1 | 3.6 | 2.4 | 3.3 |
| .064" | — | 9.9 | 6.5 | 4.5 | 2.5 | 3.3 |
| .081" | — | 12.5 | 8.1 | 5.7 | 3.1 | 3.3 |
| .091" | — | — | 9.1 | 6.3 | 3.5 | 3.3 |
| .102" | — | — | 10.3 | 7.1 | 3.9 | 3.3 |
| .128" | — | — | 12.9 | 8.9 | 4.9 | 3.3 |
Rivets per inch of width “W”, 2117-T4 (AD) protruding-head rivets. “—” means the AC gives no value for that combination.
AC 43.13-1B Table 4-11
5052 sheet, all hardnesses.
| Sheet t | 3/32 | 1/8 | 5/32 | 3/16 | 1/4 | AN-3 bolt |
|---|---|---|---|---|---|---|
| .016" | 6.3 | 4.7 | — | — | — | — |
| .020" | 6.3 | 4.7 | 3.8 | — | — | — |
| .025" | 6.3 | 4.7 | 3.8 | — | — | — |
| .032" | 6.3 | 4.7 | 3.8 | 3.2 | — | — |
| .036" | 7.1 | 4.7 | 3.8 | 3.2 | 2.4 | — |
| .040" | 7.9 | 4.7 | 3.8 | 3.2 | 2.4 | — |
| .051" | 10.1 | 5.6 | 3.8 | 3.2 | 2.4 | — |
| .064" | 12.7 | 7.0 | 4.6 | 3.2 | 2.4 | — |
| .081" | — | 8.9 | 5.8 | 4.0 | 2.4 | 3.2 |
| .091" | — | 10.0 | 6.5 | 4.5 | 2.5 | 3.2 |
| .102" | — | 11.2 | 7.3 | 5.1 | 2.8 | 3.2 |
| .128" | — | — | 9.2 | 6.4 | 3.5 | 3.2 |
Rivets per inch of width “W”, 2117-T4 (AD) protruding-head rivets. “—” means the AC gives no value for that combination. In the AC's text the 0.016" row has one fewer entry than the others; it is read here as values for 3/32" and 1/8" only.
Limits — when NOT to use this
The tables cover one kind of joint: a single-lap splice of aluminum sheet, carried in tension, with AD rivets.
- Approved data governs. AC 43.13-1B par. 4-57g puts the manufacturer's maintenance manual first and its own tables third. Where an SRM gives a repair, use it.
- AD protruding-head rivets only. The counts were calculated for 2117-T4. Countersunk rivets, DD or other alloys, and blind rivets have different allowables and are not covered by a table lookup.
- Tension in the sheet only. Rivets are not to be placed in tension — loads that pull the heads off (par. 4-57g(3)). Joints with significant bending, pressure or fatigue loading need a design, not a table.
- Thickness up to 0.128". Past the last row the calculator stops rather than extrapolate.
- The count is not the pattern. It tells you how many rivets; the edge distance and spacing rules decide where they go. The row check here is a fit test, not a layout.
- The bearing/shear label is inferred. The AC marks the boundary with an underline that does not survive in its text. The calculator reads it from where the column stops being flat, which matches the AC's stated basis but is not printed in it.
Questions people actually ask
How many rivets do I need for a doubler or patch?
Work out the width of sheet the patch has to carry, read the rivets per inch for the sheet thickness and rivet size, and multiply. On a patch over a cut or a cleaned-out hole, that count goes on each side of the damage: the load has to get from the skin into the patch, and back out again.
Can I use fewer rivets on a frame or stringer?
The table notes allow it: 60% for intermediate frames, 80% for stringers in the upper surface of a wing or in a fuselage. In the AC's Figure 4-20 example, a 0.040" 2017-T3 flange leg 0.6" wide needs 0.6 × 6.2 = 3.72, so 4 rivets; 60% of that is 2.4, and the AC uses 3 on each side of the cut.
What is the shear strength of an AD rivet?
The tables do not give it as a number. The engineering notes give the basis instead: rivet shear allowable as a percentage of the sheet's allowable tensile stress, 40% for Table 4-9 and 70% for 5052 in Table 4-11. AC par. 4-57g(2) sends you to MIL-HDBK-5 for the allowables themselves.
Why does a bigger rivet cut the count more in some cases than others?
It depends on what fails first. Rivet count falls in proportion to diameter in bearing, but with the square of diameter in shear — so stepping up a size pays most where the rivet shears first.
Clad 2024-T3 is in two tables. Which do I use?
The AC does not say. Table 4-9 names clad 2024-T3 sheet; Table 4-10 names Alclad 2024-T3 sheet. The AC's worked example uses 4-10, which needs fewer rivets. Using 4-9 costs a few rivets and removes the question.
Sources
- FAA AC 43.13-1B CHG 1, Chapter 4, Tables 4-9, 4-10 and 4-11 — every rivets-per-inch figure on this page, the 80% / 60% / 75% notes, and the engineering notes on how the tables were calculated. Par. 4-58g is the worked example; Figure 4-20 the frame splice.
- FAA AC 43.13-1B CHG 1, par. 4-57g — the order of authority for a rivet pattern (manufacturer's manuals, then MIL-HDBK-5 allowables, then the AC tables) and the rule of a rivet diameter about three times the thicker sheet.
- FAA-H-8083-31, AMT Handbook — Airframe, Volume 1, Chapter 4 — “the rivet diameter should be at least two and a half to three times the thickness of the thicker sheet,” and why: a rivet too large bulges thin sheet, one too small cannot carry the load.
Rivet layout card, printable
Edge distance, pitch and transverse pitch for all five common rivet sizes on one page, inches and mm. Sized for a toolbox lid.