# Boring Thickness Measurement Guide

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This guide collects best practices, common pitfalls, and troubleshooting steps for the Boring Thickness Module. For the standard workflow see [How to Measure with Boring Thickness Module](rhopoint-appearance-elements-using-aesthetix-with-ae-aesthetix-modules-boring-thickness-module-how-to-measure-with-boring-thickness-module.md), and for manual placement see [Boring Thickness Manual Mode](rhopoint-appearance-elements-using-aesthetix-with-ae-aesthetix-modules-boring-thickness-module-boring-thickness-manual-mode.md).

### Sample Preparation

The quality of the boring measurement depends almost entirely on the quality of the drilled crater. Aesthetix can only measure what is visible in the image.

- **Use a sharp, clean drill bit.** A worn bit produces an irregular cone and frayed layer edges.
- **Drill at a stable, perpendicular angle** to the coating surface. A tilted drill produces an **elliptical** crater whose rings are no longer truly concentric and whose radii do not match the cone geometry — the calculated thicknesses will be biased.
- **Drill deep enough** to reach into the substrate. The outermost ring must correspond to the original coating surface; the innermost ring must lie clearly within the deepest layer (or in the substrate itself).
- **Clean the crater** with a soft brush or compressed air. Drill swarf and dust create false features that confuse automatic detection.

### Imaging the Crater

- Always run **Auto-Exposure** before measuring. Boundaries between layers of similar colour are very sensitive to exposure.
- If the coating colours are such that an inner layer is **darker** than the layer above it (for example, dark primer under a lighter topcoat), enable **Invert Image** in the properties panel — see [Boring Thickness Parameters](rhopoint-appearance-elements-using-aesthetix-with-ae-aesthetix-modules-boring-thickness-module-boring-thickness-parameters.md).
- Centre the crater in the live image. Rings near the image edge are subject to greater lens distortion and their radii will be slightly biased.

### Choosing the Drill Angle

The Drill Angle parameter must exactly match the physical angle of the drill bit used. Common bits are engraved with their angle.

| Drill Angle | Magnification of layer thickness |
|---|---|
| 5.7° | × 10  (Δr × 0.0997 ≈ Δr / 10) |
| 10°  | × 5.67 |
| 20°  | × 2.75 |
| 30°  | × 1.73 |

Smaller angles "stretch" thin layers over a wider radial distance and are preferred for thin coatings; larger angles concentrate the crater and are preferred for thick coatings on small samples. See [Drill Angle](glossary-of-measurement-parameters-drill-angle.md) in the glossary.

### Center Mode — When Locked and When Free

- **Locked (recommended default):** Use for any correctly drilled, geometrically concentric crater. Center Lock removes subpixel detection noise that would otherwise produce slightly offset rings.
- **Free:** Use only when you deliberately want to follow visibly non-concentric rings, for example to investigate a tilted drill or an asymmetric crater.

![](../_images/20260611164621-TBD-boring-centre-locked.png)

### Verifying the Result

After the measurement is calculated, the overlay shows numbered layer labels between adjacent rings and a "Layers:" summary in the top-left corner of the result image. Cross-check:

- **Layer count.** The module produces N − 1 layers from N rings. If you expected three layers but the table shows two, one ring is missing.
- **Plausibility of values.** Typical decorative paint layers are in the range of 10–80 µm; primers may be 20–60 µm; industrial heavy-duty coatings can reach several hundred µm. Values orders of magnitude off this range usually point to a wrong Drill Angle.
- **Total Depth.** Compare the total depth to an independent non-destructive thickness measurement on the same sample, if available.

### Troubleshooting

| Symptom | Likely cause | Fix |
|---|---|---|
| Automatic detection finds no rings | Crater too dark, too bright, or filled with swarf | Re-run Auto-Exposure; clean the crater; try Invert Image |
| Automatic detection misses one ring | Low contrast between two adjacent layers | Add the missing ring manually — see [Boring Thickness Manual Mode](rhopoint-appearance-elements-using-aesthetix-with-ae-aesthetix-modules-boring-thickness-module-boring-thickness-manual-mode.md) |
| Rings slightly offset from each other | Subpixel detection noise on a concentric crater | Enable Center Lock |
| Rings clearly off-centre | Drill held at an angle, crater is elliptical | Re-drill perpendicular; results from a tilted crater are biased |
| Layer thicknesses one order of magnitude wrong | Drill Angle parameter does not match the physical bit | Check engraved angle on the bit; correct the Drill Angle in properties; press Set |
| Layer thicknesses are wrong but proportional | mm/pixel calibration of the Aspec camera is off | Recalibrate the device — see the calibration section of the Aesthetix manual |
| More than five visible layers | Module table stores only Layer 1–5 Depth | Plan ahead: drill only the layers you need to resolve, or export the raw layer depth list |

### When Not to Use This Module

- For routine total dry-film thickness on a known coating, a non-destructive magnetic or eddy-current gauge is faster, non-destructive, and sufficient.
- For very thin coatings (< 5 µm total) the radial spread of the rings is below the lateral resolution of the Aspec camera and the measurement becomes unreliable.
- For samples where the substrate is not visually distinguishable from the deepest coating layer, the innermost ring cannot be placed reliably.