Machine Kinematics Questions and Answers – Law of Gearing – 2

This set of Machine Kinematics Questions and Answers for Campus interviews focuses on ” Law of Gearing – 2″.

1. A side and face cutter 125 mm diameter has 10 teeth. It operates at a cutting speed of 14 m/min with a table traverse 100 mm/min. The feed per tooth of the cutter is
a) 10 mm
b) 2.86 mm
c) 0.286 mm
d) 0.8 mm

Explanation: пDN = 14,
N = 14000/3.14 x 125 = 35.65
Feed for tooth = table traverse/ N x no. of teeth = 100/35.65 x 10 = 0.286 mm.

2. Consider the following statements in case of reverted gear train:
1. The direction of rotation of the first and the last gear is the same.
2. the direction of rotation of the first and the last gear is opposite.
3. The first and the last gears are on the same shaft.
4. The first and the last gears are on separate but co-axial shafts.
Which of these statements is/are correct?
a) 1 and 3
b) 2 and 3
c) 2 and 4
d) 4 alone

Explanation: Only fourth statement is correct.

3. The dynamic load on a gear is due to
1. inaccurancies of tooth spacing
2. irregularities in tooth profile
3. deflection of the teeth under load
4. type of service
Which of the above statements are correct?
a) 1,2 and 3
b) 2,3 and 4
c) 1,3 and 4
d) 1,2 and 4

Explanation: The dynamic load on a gear is due to
1. inaccurancies of tooth spacing
2. irregularities in tooth profile
3. deflection of the teeth under load.

4. Consider the following statements:
A 200 stub tooth system is generally preferred in spur gears as it results in
1. stronger teeth
2. lesser number of teeth on the pinion
3. lesser chances of surface fatigue failure
4. reduction of interference
Which of the above statements are correct?
a) 1,2 and 4
b) 3 and 4
c) 1 and 3
d) 1,2,3 and 4

Explanation: A 200 stub tooth system is generally preferred in spur gears as it results in
1. stronger teeth
2. lesser number of teeth on the pinion
3. reduction of interference.

5. An involute rack with 200 pressure angle meshes with a pinion of 14.50 pressure angle.
a) True
b) False

Explanation: Such a matching is impossible.

6. When a pair of spur gears of the same material is in mesh, the design is based on pinion.
a) True
b) False

Explanation: For a pair of gears of the same material in mesh, the strength factor of the pinion is less than that of the gear.

7. Consider the following modifications regarding avoiding the interference between gears:
1. The centre distance between meshing gears be increased
2. Addendum of the gear be modified
3. Teeth should be undercut slightly at the root
4. Pressure angle should be increased
5. Circular pitch be increased
Which of these are effective in avoiding interference?
a) 1,2 and 3
b) 2,3,4 and 5
c) 1,4 and 5
d) 3,4 and 5

Explanation: None.

8. In a reverted gear train, two gears P and Q are meshing, Q-R is a compound gear, and R and S are meshing. The modules of P and R are 4 mm and 5 mm respectively. The numbers of teeth in P, Q and r are 20, 40 and 25 respectively. The number of teeth in S is
a) 23
b) 35
c) 50
d) 53

Explanation: C = 1/2m1(zp + zq) = 1/2m2(zr + zs)
4(20 + 40) = 5(25 + zs)
zs = 23.

9. When two spur gears having involute profiles on their teeth engage, the line of action is tangential to the
a) pitch circles
b) dedendum circles
d) base circles

Explanation: None.

10. If the annular wheel of an epicyclic gear train has 100 teeth and the planet wheel has 20 teeth, the number of teeth on sun wheel is
a) 80
b) 60
c) 40
d) 20

Explanation: 2dp + ds = da
2zp + zs = za
2 x 20 + zs = 100
zs = 60.

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