# Drilling an Oval Thumb

## 3 Measurements

- ##### Smallest - Starting bit
- ##### Largest - Width of oval
- ##### Oval direction

[![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/S81image.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/S81image.png)

## Taper base of thumb

- ##### Measure the base of the thumb
- ##### Start with that bit
- ##### Go down 1/8'' max
- ##### 1/32 step downs
- ##### Go till the starting bit


[![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/ZqZimage.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/ZqZimage.png)

[![image.png](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/scaled-1680-/wpAimage.png)](https://wiki.spectrebowling.com/uploads/images/gallery/2025-05/wpAimage.png)

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![](https://wiki.spectrebowling.com/loading.gif)