# Drill Angle

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**Drill Angle** is the cone angle of the Säberg drill bit used to prepare a sample for layer-resolved coating thickness measurement with the [Boring Thickness Module](rhopoint-appearance-elements-using-aesthetix-with-ae-aesthetix-modules-boring-thickness-module.md).

### Definition

The Drill Angle is the full angle between the cone surface of the drill bit and the perpendicular to the coating surface. It is a physical property of the drill bit and is normally engraved on the bit by its manufacturer.

### Why It Matters

The Boring Thickness Module converts the radial distance between adjacent ring boundaries (visible in the image of the drilled crater) into a layer thickness using:

> **Layer thickness [µm]** = | r_outer − r_inner | × tan(Drill Angle) × mm/pixel × 1000

The calculated thickness is therefore directly proportional to `tan(Drill Angle)`. Entering the wrong angle produces plausible-looking but incorrect µm values without any warning from the software.

### Typical Values

| Drill Angle | Magnification factor (1 / tan) | Preferred for |
|---|---|---|
| 5.7° | × 10.04 | Thin coatings, layered systems with sub-50 µm layers |
| 10°  | × 5.67  | General multi-layer paint systems |
| 20°  | × 2.75  | Thicker industrial coatings |
| 30°  | × 1.73  | Very thick coatings on small samples |

### In Appearance Elements

- **Parameter location:** Boring Thickness module → properties panel → Drill Angle
- **Default:** 5.7°
- **Allowed range:** 0° – 90°

See also: [Boring Thickness Parameters](rhopoint-appearance-elements-using-aesthetix-with-ae-aesthetix-modules-boring-thickness-module-boring-thickness-parameters.md), [Layer Depth](glossary-of-measurement-parameters-layer-depth.md), [Total Depth](glossary-of-measurement-parameters-total-depth.md).