Question:medium
An engineering student is fabricating a setup and needs a key for connecting a shaft to the hub of a rotating machine element. The student uses a sunk key which is tapered and prevents relative axial motion.
Which ONE of the following keys did the student most likely use?
An engineering student is fabricating a setup and needs a key for connecting a shaft to the hub of a rotating machine element. The student uses a sunk key which is tapered and prevents relative axial motion.
Which ONE of the following keys did the student most likely use?
Which ONE of the following keys did the student most likely use?
Show Hint
Sunk keys are cut into both shaft and hub; only the tapered ones resist axial sliding.
Updated On: Aug 5, 2026
- Saddle key
- Woodruff key
- Feather key
- Gib-head key
Show Solution
The Correct Option is D
Solution and Explanation
Step 1: Sort the four keys into two groups first:
Group by whether the key is sunk (cut into both shaft and hub) or not, and whether it is tapered or parallel in cross-section.
Saddle key: not sunk, sits on the shaft surface, held by friction only.
Woodruff key: sunk, half-disc shape, mainly used for self-alignment on tapered or small shafts.
Feather key: sunk, parallel (uniform) cross-section, made to allow sliding.
Gib-head key: sunk, tapered cross-section, made to be driven in tight.
Step 2: Apply the "sunk" filter:
The question says the key is a sunk key, so the saddle key is out right away since it is not a sunk key at all.
That leaves woodruff, feather, and gib-head keys still in the running.
Step 3: Apply the "tapered and locks axial motion" filter:
The feather key is deliberately parallel, its whole job is to let the hub move axially while still turning with the shaft, so it cannot be the answer to a question that wants axial motion prevented.
The woodruff key is also not the tapered wedge type described here, it is chosen mainly for alignment on small or tapered shaft ends.
The gib-head key is the one built with a taper along its length, and once it is hammered in, the wedge action locks the hub axially in place, exactly matching "tapered" and "prevents relative axial motion."
\[ \text{Sunk keys: Woodruff, Feather, Gib-head} \;\rightarrow\; \text{Tapered + locks axially: Gib-head only} \]
Final Answer:
Filtering step by step on sunk, then tapered, then axial-locking behavior isolates one key. \[ \boxed{\text{Gib-head key}} \]
Group by whether the key is sunk (cut into both shaft and hub) or not, and whether it is tapered or parallel in cross-section.
Saddle key: not sunk, sits on the shaft surface, held by friction only.
Woodruff key: sunk, half-disc shape, mainly used for self-alignment on tapered or small shafts.
Feather key: sunk, parallel (uniform) cross-section, made to allow sliding.
Gib-head key: sunk, tapered cross-section, made to be driven in tight.
Step 2: Apply the "sunk" filter:
The question says the key is a sunk key, so the saddle key is out right away since it is not a sunk key at all.
That leaves woodruff, feather, and gib-head keys still in the running.
Step 3: Apply the "tapered and locks axial motion" filter:
The feather key is deliberately parallel, its whole job is to let the hub move axially while still turning with the shaft, so it cannot be the answer to a question that wants axial motion prevented.
The woodruff key is also not the tapered wedge type described here, it is chosen mainly for alignment on small or tapered shaft ends.
The gib-head key is the one built with a taper along its length, and once it is hammered in, the wedge action locks the hub axially in place, exactly matching "tapered" and "prevents relative axial motion."
\[ \text{Sunk keys: Woodruff, Feather, Gib-head} \;\rightarrow\; \text{Tapered + locks axially: Gib-head only} \]
Final Answer:
Filtering step by step on sunk, then tapered, then axial-locking behavior isolates one key. \[ \boxed{\text{Gib-head key}} \]
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