Threads and fasteners: A thread that is formed on the inside surface of a cylindrical or tapered hole (for example, a tapped hole) is called what type of thread?
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ABasic thread
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BExternal thread
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CInternal thread
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DMajor diameter thread
Answer
Correct Answer: Internal thread
Explanation
Introduction / Context:Screw threads may occur on bolts (external) or in tapped holes and nuts (internal). Correct terminology ensures accurate callouts, tooling, and inspection.
Given Data / Assumptions:
- The thread is located inside a part (for example, a nut or a tapped hole).
- We distinguish between internal versus external thread forms.
- Standard terms are used (major/minor diameters describe sizes, not locations).
Concept / Approach:
An internal thread is machined or formed on the interior surface and mates with an external thread. Drawings specify series (e.g., UNC/UNF), size, class (e.g., 2B for internal), and depth or through condition.
Step-by-Step Solution:
Identify thread location: inside the member.Apply standard nomenclature: internal thread on the inside, external thread on a bolt or screw.Select “Internal thread.”Verification / Alternative check:
Standards (such as ASME/ISO) use “A” classes for external and “B” for internal in Unified threads, reinforcing the location-based terminology.
Why Other Options Are Wrong:
Basic thread: generic phrase, not a location.
External thread: opposite of inside location.
Major diameter thread: refers to the largest diameter of a thread, not the thread’s location.
Common Pitfalls:
Confusing diameter terms (major/minor/pitch) with internal/external classification.
Final Answer:
Internal thread