Quick Answer
Choose a spindle diameter that balances ease of drilling and durability, typically between 1/4 inch (6-7 mm) and 1/2 inch (13 mm). A smaller diameter is ideal for finer details, while a larger diameter allows for faster drilling.
Material Considerations
When choosing the right diameter for your spindle, consider the type of wood you’ll be drilling. Hardwoods like oak or maple require a slightly larger diameter, around 1/4 inch (6-7 mm), to generate enough torque. Softwoods, on the other hand, can be drilled with a narrower spindle, around 3/16 inch (4.5-5 mm).
Measuring and Marking
To ensure accurate measurements, use a caliper to measure the diameter of your spindle. Mark the desired length on the spindle using a sharp pencil or a marker. A precise mark will help you achieve consistent results. For a fire bow drill, a spindle length of 12-18 inches (30-45 cm) is recommended.
Drilling Technique
During the drilling process, apply gentle to moderate pressure, increasing the pressure as needed. Use a consistent, smooth motion, applying even pressure to avoid splintering the wood. For a fire bow drill, aim for a smooth, consistent hole depth of 1-2 inches (2.5-5 cm).
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