Machine Design Multiple Choice Questions on “System of Gear Tooth”.
1. There are ____ standard systems for the shape of gear teeth.
a) 1
b) 2
c) 3
d) 4
Answer: c
Clarification: 14.5⁰ full depth involute system, 20⁰ full depth involute system and 20⁰ stub involute system.
2. When the number of teeth reaches infinity, circle radius approaches infinity the gear becomes an infinite loop.
a) True
b) False
Answer: b
Clarification: It becomes a rack with straight sided teeth.
3. Which of the following statements are not true?
a) Increasing pressure angle improves the tooth strength
b) Contact duration is decreased with increase in pressure angle
c) 20⁰ pressure angle has quieter operation then 14.5⁰
d) All of the statements are true
Answer: c
Clarification: Lower the pressure angle, quieter is the operation. Lower the pressure angle, lower is the breadth of the tooth at root.
4. 20⁰ stub involute system have comparatively smaller interference.
a) True
b) False
Answer: a
Clarification: They have shorter addendum and shorter dedendum.
5. Which of the following have stronger teeth?
a) Stub teeth
b) Full depth teeth
c) Both have equal strength
d) Can’t be determined
Answer: a
Clarification: Smaller moment arm of bending force leads to stronger stub teeth.
6. As the module increases, index of size of gear decreases.
a) True
b) False
Answer: b
Clarification: Module is the measure of size of index of the gear tooth.
7. Crowning is an abrasive process that debars the gear strength.
a) True
b) False
Answer: b
Clarification: Crowningis used to strengthen the tooth.
8. Inaccuracies in tooth profile lead to concentration of pressure on the middle of tooth.
a) True
b) False
Answer: b
Clarification: Inaccuracies lead to shift of pressure at the end of tooth which can be improved by crowning.
9. A pair of spur gears consist of 25 teeth pinion meshing with a 115 teeth gear. The module is 5mm. Calculate the centre distance.
a) 280mm
b) 269mm
c) 350mm
d) 305mm
Answer: a
Clarification: C=m(z(p)+z(g))/2.
10. A pair of spur gears consist of 25 teeth pinion meshing with a 115 teeth gear. The module is 5mm. Calculate pitch circle diameter of the pinion.
a) 95mm
b) 105mm
c) 115mm
d) 125mm
Answer: d
Clarification: D=5×25.
11. A pair of spur gears consist of 25 teeth pinion meshing with a 115 teeth gear. The module is 5mm. Calculate the pitch circle diameter of the gear.
a) Cannot be determined
b) 31mm
c) 475mm
d) 575mm
Answer: d
Clarification: D=5×115.
12. A pair of spur gears consist of 25 teeth pinion meshing with a 115 teeth gear. The module is 5mm. Calculate the addendum.
a) None of the listed
b) 4.75mm
c) 5.25mm
d) 5mm
Answer: d
Clarification: H=m=5mm.
13. A pair of spur gears consist of 25 teeth pinion meshing with a 115 teeth gear. The module is 5mm. Calculate the dedendum.
a) 4.75mm
b) 5mm
c) 6.25mm
d) 6.68mm
Answer: c
Clarification: H=1.25xm=1.25x5mm.
14. A pair of spur gears consist of 25 teeth pinion meshing with a 115 teeth gear. The module is 5mm. Calculate the tooth thickness.
a) 6.23mm
b) 5.44mm
c) 7.854mm
d) 8.16mm