21. The pipe joint mostly used for pipes carrying water at low pressures is-
A. socket joint
B. nipple joint
C. spigot and socket joint
D. union joint
22. The helix angle for single helical gears ranges from-
A. 10° to 15°
B. 15° to 20°
C. 20° to 35°
D. 35° to 45°
23. Surface endurance limit of gear material is dependent upon its-
A. yield strength
B. Brinell hardness number
C. elastic strength
D. toughness
24. The railway carriage couplings have-
A. square threads
B. buttress threads
C. acme threads
D. knuckle threads
25. If a bearing is designated by the number 305, it means that the bearing is of-
A. medium series whose bore is 5 mm
B. light series whose bore is 5 mm
C. light series whose bore is 25 mm
D. medium series whose bore is 25 mm