Taps and chamfer lengths Which statement correctly describes a taper tap used to start internal threads in a blind or through hole?

Introduction / Context:Hand tapping generally uses a set of three: taper (starter), plug (second), and bottoming taps. The chamfer length determines how gradually the tap engages, affecting alignment, torque, and chip load.

Given Data / Assumptions:

• Taper tap is the first tap in the sequence.
• Used to initiate thread form accurately and reduce starting torque.

Concept / Approach:The taper tap has the longest chamfer, typically 8–10 threads, which gradually forms the thread. The plug tap follows with about 3–5 chamfered threads, and the bottoming tap has 1–2, enabling threads to the bottom of a blind hole.

Step-by-Step Solution:Identify function: start the thread straight with low torque.Require long lead-in: hence 8–10 thread chamfer on taper tap.Confirm other tap types: plug (3–5), bottoming (1–2).

Verification / Alternative check:Workshop charts and tap manufacturers specify typical chamfer ranges consistent with the above.

Why Other Options Are Wrong:

• 3–4 threads describes a plug tap more closely.
• Full threads/no chamfer would make starting nearly impossible.
• Bottoming and taper taps are not identical; they serve different stages.

Common Pitfalls:Trying to start a hole with a bottoming tap; misalignment causing cross-threading.

Final Answer:Its end is tapered over about eight to ten threads