Tapping tool geometry – bottoming tap identification Which feature best characterizes a bottoming tap used to cut threads to the bottom of a blind hole?

Introduction / Context:
Taps are commonly supplied in three chamfer forms: taper (long chamfer), plug (intermediate chamfer), and bottoming (short chamfer). Correct selection is essential when cutting threads to the full depth in blind holes.

Given Data / Assumptions:

• Standard hand or machine taps are considered.
• Blind hole requires threads close to the bottom.
• Material and lubrication are appropriate for tapping.

Concept / Approach:
A bottoming tap has very little chamfer (typically 1–1.5 threads) so that full-depth threads can be formed almost to the hole bottom. By contrast, a plug tap has about 3–5 threads of chamfer and is used for general tapping, while a taper tap has about 7–10 chamfered threads for easy starting but cannot cut full depth near the bottom.

Step-by-Step Solution:
Identify the need: fully formed threads near the bottom of a blind hole.Select the tap with minimal chamfer: bottoming tap.Relate to options: “full threads almost to the end (minimal chamfer)” matches bottoming tap geometry.

Verification / Alternative check:
Tap charts specify chamfer lengths: taper (long), plug (intermediate), bottoming (shortest), confirming the identification.

Why Other Options Are Wrong:
3–4 chamfered threads describe plug taps; 8–10 describes taper taps. Spiral flutes and coolant holes are design features independent of the “bottoming” designation.

Common Pitfalls:
Starting a blind hole with a bottoming tap can be difficult; begin with a taper or plug tap and finish with a bottoming tap to reach full depth.

Final Answer:
Full threads almost to the end (minimal chamfer)