The calculator
Runs in your browser. Inches or millimetres at the top. Measure the shop head across its widest point and from the sheet to the top of the head, with a rivet gauge or callipers, not the eye.
How the standards work
The shop head is the acceptance test. The FAA Airframe Handbook calls the size of the formed head “the visual standard of a proper rivet installation”, and it is checked with “a scale or rivet gauge”. A rivet that was the right length and the right diameter can still be driven badly; the head is where it shows.
Two sources, two lines. AC 43.13-1B Figure 4-6(a) gives a formed head at least 1½D wide and at least ½D high, drawn at 0.65D. The Airframe Handbook, Figure 4-76, gives a band instead: from a minimum of 1.25D wide by 0.66D high — barely driven — through a preferred 1.5D × 0.5D, to a maximum of 1.66D × 0.33D — as flat as it may go. The Handbook's preferred head is the AC's minimum. A head 1.4D wide passes the Handbook and fails the AC.
Which to work to. AC 43.13-1B is the FAA's acceptable data for repairs where there is no manufacturer's data; the Handbook is a training text. Where you are working to the AC, the AC's minimum applies. The calculator reports both, and flags the band where they disagree.
Width and height move together. Driving spreads a fixed amount of metal: as the head gets wider it gets flatter. That is why the Handbook's maximum has the widest and lowest head, and why a measurement that is both wide and tall usually means the height was measured wrong.
D, E and M rivets are tighter. For the harder alloys the Handbook narrows the band: preferred 1.4D × 0.6D, maximum 1.5D × 0.5D, and a shorter pre-drive protrusion of 1.25D to 1.33D, against 1.33D to 1.5D for A, AD, B and DD.
Shop head limits by rivet size — A, AD, B, DD
From the FAA Airframe Handbook, Figure 4-76. Width runs from the least-driven to the most-driven acceptable head; height runs the other way.
| Rivet | Width min | Width preferred | Width max | Height min (flattest) | Height preferred | Height at min width |
|---|---|---|---|---|---|---|
| 3/32" | 0.117" | 0.141" | 0.156" | 0.031" | 0.047" | 0.062" |
| 1/8" | 0.156" | 0.188" | 0.207" | 0.041" | 0.062" | 0.083" |
| 5/32" | 0.195" | 0.234" | 0.259" | 0.052" | 0.078" | 0.103" |
| 3/16" | 0.234" | 0.281" | 0.311" | 0.062" | 0.094" | 0.124" |
| 1/4" | 0.312" | 0.375" | 0.415" | 0.083" | 0.125" | 0.165" |
AC 43.13-1B Figure 4-6(a) sets the minimum at the preferred column: 1.5D wide and 0.5D high, together.
Worked example
A 1/8" AD rivet. The shop head measures 0.175" across and 0.075" high.
- Width: 0.175 ÷ 0.125 = 1.40D. Height: 0.075 ÷ 0.125 = 0.60D.
- Handbook band for AD: 1.25D to 1.66D wide, 0.33D to 0.66D high. Inside it.
- AC 43.13-1B: at least 1.5D wide. 1.40D is short of it, by 0.013".
Acceptable to the Handbook, not to the AC. On a repair done to AC 43.13-1B, this head is under-driven. Whether more driving can bring it to 1.5D depends on how far the rivet has work-hardened; if it cannot, it is drilled out and replaced.
Limits — when NOT to use this
For solid aluminum rivets driven with a gun and bucking bar, or squeezed.
- Approved data governs. Where the manufacturer's manual or a repair drawing gives shop head dimensions, use them.
- Not for blind rivets, Hi-Loks or lockbolts. Their installation is checked against the manufacturer's gauges and data, not a formed head.
- Size is necessary, not sufficient. A head of the right size can still be cracked, cocked or cut. Check both.
- Measure, do not estimate. A difference of 0.01" moves a 1/8" rivet across a limit.
- The defect list is the FAA's common cases. AMT Figure 4-97 and AC 43.13-1B Figure 4-6(c). Anything outside them, or any doubt about a rivet in primary structure, goes to the inspector.
Questions people actually ask
What size should a rivet shop head be?
1.5 times the shank diameter wide and 0.5 times high. On a 1/8" rivet that is 0.188" by 0.063". That is AC 43.13-1B's minimum and the Airframe Handbook's preferred size.
Is a 1.3D shop head acceptable?
To the FAA Airframe Handbook, yes: its minimum for A, AD, B and DD rivets is 1.25D wide. To AC 43.13-1B, no: its minimum is 1.5D. Which applies depends on the data you are working to.
How much shank should stick out before driving?
AC 43.13-1B shows 1.5D, with 1D as the minimum. The Airframe Handbook gives 1.33D to 1.5D for A, AD, B and DD rivets, and 1.25D to 1.33D for D, E and M.
What causes a smiley on a rivet head?
The rivet set slipping off the head, usually because driving started too fast or the set was not held square. The Handbook's remedy is to replace the rivet.
Do I need a bigger rivet when I replace one?
Only if the hole is damaged. Drilled out carefully through the manufactured head, the hole keeps its size and the same rivet goes back. If the hole has elongated, the Handbook calls for the next size up, 1/32" larger.
Sources
- FAA AC 43.13-1B CHG 1, Chapter 4, Figure 4-6 — (a) formed head 1½D minimum width, ½D minimum height (0.65D drawn), pre-drive length 1½D with 1D minimum; (c) rivet imperfections and their causes. Par. 4-57d refers to the figure.
- FAA-H-8083-31, AMT Handbook — Airframe, Volume 1, Chapter 4, Figure 4-76 and pp. 4-44 to 4-46 — driven rivet standards: minimum, preferred and maximum formed heads and pre-drive protrusion for A, AD, B, DD and for D, E (KE), M rivets; Figure 4-97, rivet defects with cause, remedy and action; evaluating, removing and upsizing rivets. P. 4-38 for the smiley and eyebrow, and driving within 3 seconds.