Drill Point Geometry: Total Depth and Full-Diameter Depth Differ

Identify the point geometry

Harvey identifies drill point angle as a distinct geometry. In an ideal conical construction, the included angle sets the axial tip length. Primary reference: Harvey technical explanation.

Calculate a fictional depth boundary

Assume an ideal pointed drill diameter of 8 mm and included point angle 118°. The half-angle is 59°. The axial cone length is (8/2)/tan59°, approximately 2.403 mm.

If the fictional tip reaches 20 mm below the surface, the simple full-diameter cylindrical portion extends about 17.597 mm. Quoting 20 mm as full-diameter depth would include the conical bottom. This model intentionally omits chisel geometry, lip details and breakout deformation; it is not an actual drilling depth instruction.

Specify which endpoint matters

Draw the cylindrical wall endpoint and deepest point separately. Record whether a requirement concerns tip depth, full bore diameter or clearance to a subsequent feature. Preserve the actual point geometry rather than assuming a flat bottom because a drawing uses one depth number.

Compare available cylindrical length with the intended mating or next-operation requirement. Actual drill form and observed hole geometry remain necessary. The worksheet makes the dimensional boundary explicit without selecting a drill, promising a finished hole tolerance or translating the illustrative depth into an executable program.

Customer Questions

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• Primary reference: Harvey technical explanation