Calculate drill point length, point geometry, effective flute depth and theoretical tip position from drill diameter and included point angle.
Enter drill diameter and point angle to calculate.
What is drill point length? It is the theoretical axial distance from the full drill diameter to the drill's point tip.
What formula is used? For a symmetric conical point, point length equals drill diameter divided by twice the tangent of half the included point angle.
What happens when the point angle increases? The drill point becomes shorter for the same drill diameter.
What happens when the point angle decreases? The drill point becomes longer for the same drill diameter.
Why is 118° commonly used? A 118° point is a common general-purpose twist-drill geometry and provides a useful balance for many drilling applications.
Why are 135° points used? A 135° point is common on many split-point and harder-material drilling tools and generally has a shorter point.
Does drill point length affect drilling depth? Yes. If the full drill diameter must reach a specified depth, the theoretical point length must be considered when estimating total drill travel or breakthrough position.
Does this account for the chisel edge? No. The calculator uses ideal conical geometry and does not model the detailed cutting-edge geometry of a specific drill.
Can this be used for CNC drilling? Yes, as a geometric planning aid. For accurate depth control, use the actual drill manufacturer's geometry and machine/tool offsets.