Drilling for tapping: When specifying tap drill depth, the calculated full-diameter depth excludes the drill's conical point; additional allowance is needed to achieve the required full thread depth. Decide whether the statement “Tap drill depth does not include the cone point” is correct.

Introduction / Context:
A standard twist drill forms a conical bottom equal to the point angle (often 118 or 135 degrees). When preparing a hole for tapping, the full-diameter depth available for threads is less than the measured drill penetration unless extra depth is added. We assess the statement that tap drill depth excludes the cone point.

Given Data / Assumptions:

• Tap drill size is chosen based on thread pitch and percentage of thread.
• Drill point leaves a conical section with insufficient diameter for full threads.
• Design often requires full thread engagement over a specified length.

Concept / Approach:
The effective threaded length begins where the hole reaches the tap drill diameter. The cone point yields a smaller diameter region that will not fully form threads; therefore, the required drill penetration equals effective thread depth plus an allowance for the cone and tap chamfer.

Step-by-Step Solution:
1) Determine required full thread length (L_effective).2) Add allowance for drill point (L_point) and tap chamfer (L_chamfer).3) Drill to depth = L_effective + L_point + L_chamfer.4) Tap to full depth, verifying engagement length.

Verification / Alternative check:
Shop practices include “drill extra” rules (e.g., add several millimeters) to compensate for the point and lead-in, confirming the exclusion of the cone from effective depth.

Why Other Options Are Wrong:
Metric-only or coarse-only limitations are false; the principle applies universally.“Incorrect”: Conflicts with hole geometry and tapping fundamentals.

Common Pitfalls:
Forgetting the allowance and ending with partial threads at the bottom; breaking taps due to insufficient clearance for chips in the cone region.

Final Answer:
Correct