What This Calculator Does
A spade drill angle depends on simple triangle geometry. The drill width forms the base. The point length forms the height. Together they create two right triangles from the center line. This calculator uses those values to find the included point angle. It also shows the half angle, bevel complement, target difference, and target point length.
Why the Angle Matters
A small angle gives a long point. It can start a hole with more guidance. It may also need extra feed space. A large angle gives a shorter point. It can reduce point height and may suit shallow starts. The best value depends on material, drill shape, machine control, and the finish you need.
Inputs You Can Control
Enter the drill width across the cutting corners. Then enter the point length from the tip to the corner line. Choose inches or millimeters. Add a target angle if you want a comparison. The tolerance field helps mark whether the current design is close enough. The material preset only fills a practical target. You can still edit the angle.
Reading the Results
The included angle is the main answer. It is the full angle at the point. The half angle is measured from the drill center line to one cutting side. The bevel complement helps when a shop gauge reads from a flat reference instead of the center line. The point length needed for the target tells you how much longer or shorter the point should be.
Practical Measuring Tips
Measure width at the same corner line used for point length. Use calipers for the width. Use a depth gauge for the point height. Keep both measurements in the same unit. Small errors can change the angle, especially on narrow drills. Record the results before grinding. Exporting a CSV or PDF makes repeat checks easier.
Common Use Cases
Use the calculator before making a custom flat drill. Use it when checking a reground point. It also helps compare two bits that look similar. Students can use it to connect trigonometry with workshop geometry. Makers can save each result and build a small reference chart for future setups. This supports consistent notes during careful drill angle planning each time.