Machine Design Questions and Answers – Keys

This set of Machine Design Multiple Choice Questions & Answers (MCQs) focuses on “Keys”.

1. A force 2P is acting on the double transverse fillet weld. Leg of weld is h and length l. Determine the shear stress in a plane inclined at θ with horizontal.
a) PSinθ(Sinθ+Cosθ)/hl
b) P(Sinθ+Cosθ)/hl
c) Pcosθ(Sinθ+Cosθ)/hl
d) None of the listed

Explanation: F=PSinθ and width=h/(Sinθ+Cosθ).

2. Maximum shear stress in transverse fillet weld of leg h and length l is
a) P/hl
b) 1.21P/hl
c) P/1.21hl
d) None of the listed

Explanation: τ= PSinθ(Sinθ+Cosθ)/hl, by maximising it θ=67.5’ and hence find corresponding τ.

3. A sunk key fits in the keyway of the _____ only.
a) Hub
b) Sleeve
c) Both hub and sleeve
d) Neither hub nor sleeve

Explanation: Sunk key fits halfway in the hub and halfway in the shaft.

4. Hollow saddle key is superior to flat saddle key as far as power transmitting capability is concerned.
a) True
b) False

Explanation: The resistance to slip in case of flat key is more.

5. Saddle key is more suitable than sunk key for heavy duty applications.
a) True
b) False

Explanation: In sunk key, relative motion is also prevented by shear resistance of sunk key and hence sunk key is recommended.
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6. The main advantage of sunk key is that it is a _____ drive.
a) Positive
b) Negative
c) Neutral
d) None of the listed

Explanation: Sunk key is a positive drive and no slip occurs.

7. Woodruff key permits _____ movement b/w shaft and the hub.
a) Axial
c) Eccentric
d) None of the listed

Explanation: Woodruff key is a sunk key and doesn’t permit axial moment.

8. Determine the length of kennedy key required to transmit 1200N-m and allowable shear in the key is 40N/mm². The diameter of shaft and width of key can be taken as 40mm and 10mm respectively.
a) 49mm
b) 36mm
c) 46mm
d) 53mm

Explanation: l=M/[dbτ√2].

9. Splines are keys.
a) True
b) False

Explanation: Splines are keys made with shafts.

10. Involute splines have stub teeth with a pressure angle of ___
a) 30
b) 45
c) 60
d) Can’t be determined