The drawing
Where to buy
Step by step
| Step | Action | What to do |
|---|---|---|
| 1 | Confirm you can dimple | Thin sheet below the countersinking minimum, and an alloy that allows it. 7075-T6, magnesium and titanium need hot dimpling. |
| 2 | Drill and deburr | A rough hole causes radial cracks. |
| 3 | Pick the dies | A separate set for each rivet size and head shape. The male die's guide is the size of the hole. |
| 4 | Set up | Rest the female die on a solid surface, sheet on top, male die through the hole. In a squeezer, adjust the dies to the sheet thickness. |
| 5 | Form it | Two or three solid hammer blows should do. Keep blows or pressure to a minimum: extra work hardens the area. |
| 6 | Check with a rivet | Head flush, sharp break from surface into the dimple, no cracks. |
Tools you need
| Tool | What for | Buying guide | Catalog |
|---|---|---|---|
| Dimple dies | One set per rivet size | Dimple dies | 1/8 die set |
| Spring-back dies | Another die type | Dimple dies | Spring-back dies |
| Squeezer | Controlled pressure | Squeezers | Hand squeezer |
Four ways to dimple
Male and female dies
- How
- Hammer or squeezer
- Use
- Normal light work
Coin
- How
- Countersunk rivet as the male die, driven with the gun; bar behind the female die
- Use
- Only if the male die is broken or missing. Drive the same rivet afterwards
Radius
- How
- Radius die sets in a squeezer
- Use
- Stationary or portable squeezers
Hot
- How
- Heated dies, usually large stationary equipment
- Use
- 7075-T6, magnesium and titanium; prevents cracks in 2024-T3
FAA-H-8083-31B pp. 4-41 to 4-43.
Which metals need heat
| Metal | Dimpling |
|---|---|
| 2024-T3 | Hot or cold; may crack after cold dimpling because of hard spots |
| 7075-T6 | Always hot |
| Magnesium alloys | Hot, low formability |
| Titanium | Hot, tough; same temperature and dwell as 7075-T6 |
FAA-H-8083-31B pp. 4-42, 4-43.
What to check when it is done
| Look at | Good | If not |
|---|---|---|
| Flushness | Sample dimples: fastener sits flush | Too shallow: check the die setting |
| Break | Sharp break into the dimple | More pressure, within reason |
| Radial cracks | Starting at the hole edge, most common in 2024-T3; small tolerance sometimes allowed | Rough hole or too deep; check the limit |
| Circumferential cracks | None, round the edge of the dimple | Cause for rejection; common in hot-dimpled 7075-T6 with too little heat |
Questions people actually ask
Is a dimpled joint weaker?
No. The Handbook says it removes no metal and, by nesting, gives a stronger joint than the non-flush type.
What is a subcountersink?
A countersink well made to receive a dimple: thin sheet dimpled into thick structure.
Limits of this guide
What the sources support, and no further.
- The manual governs. Where the SRM, the drawing or the fastener maker says otherwise, follow them; this page explains general practice.
- No temperatures here. The Handbook gives none; they come from the machine or the SRM.
Where to buy
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Distributors coming soon.
Sources
- FAA-H-8083-31B, Aviation Maintenance Technician Handbook: Airframe, Chapter 4 — p. 4-36, dies; pp. 4-41 to 4-43, dimpling; Figs. 4-93, 4-95, 4-96.
Educational reference only. not approved data. Always consult the applicable SRM, AMM, or AC 43.13-1B and your certifying authority.