Drill Point Length Calculator
Calculate geometric twist-drill point length, tip allowance and drill travel for a required full-diameter hole depth.
Results use the inputs above; example values are illustrative and are not tool-specific speed/feed recommendations.
Formulas and Calculation Method
Point length = (D/2) / tan(included angle/2); total axial tip travel = hole depth + point length.
A twist drill has a conical point whose axial height is determined by the drill diameter and included tip angle. For a 118° point, the theoretical allowance is about 0.3004 times the diameter. The calculator provides a useful geometric allowance when specifying full-diameter blind-hole depth.
Important Assumptions and Limitations
Assumes an ideal conical point with no web, chisel or split-point modification. Through-hole breakthrough and blind-hole tolerance must be considered separately. Always check the actual drill geometry.
Frequently Asked Questions
What changes if I use a 135° drill?
A wider included point angle produces a shorter theoretical point length.
Is this the same as hole depth in a CNC cycle?
Not necessarily; the programmed Z depth depends on how the tool length and hole depth are defined.
Need the Right Cutting Tool?
Match this calculation to your workpiece material, machine setup and required tooling dimensions. Explore ONMY tools or share your application for a quotation.
Explore Holemaking ToolsRequest a QuoteTechnical references: Machining Doctor — Drilling Formulas. Calculations are independently implemented for ONMY; source links do not imply endorsement.
