The efficiency of a square threaded screw is maximum if the helix angle is equal to (Where φ = Angle of friction)
90° - φ
45° - φ
45° - φ/2
45° + φ/2
Correct Answer :
C. 45° - φ/2
Related Questions
The toughness of a material _________ when it is heated
Does not change
Increases
Decreases
None of the Above
Screws used for power transmission should have
Very fine threads
High efficiency
Low efficiency
Strong teeth
The contact ratio is the ratio of
Length of arc of recess to the circular pitch
Length of path of contact to the circular pitch
Length of arc of contact to the circular pitch
Length of arc of approach to the circular pitch
The most important dimension in the design of a nut is
Pitch diameter
Inside diameter
Outside diameter
Height
The rolling contact bearings as compared to sliding contact bearings have
Low starting and low running friction except at very high speeds
Accuracy of shaft alignment
Small overall dimensions
All of the above
When a circular beam of diameter d is subjected to a shear force F, the maximum shear stress induced will be
4F/ πd²
6F/ πd²
8F/ πd²
16F/ 3πd²
According to Indian standard specifications, 100 H6/g5 means that
Tolerance grade for the hole is 6 and for the shaft is 5
Tolerance grade for the shaft is 6 and for the hole is 5
Tolerance grade for the shaft is 4 to 8 and for the hole is 3 to 7
Tolerance grade for the hole is 4 to 8 and for the shaft is 3 to 7
The taper on key is given on
Bottom side only
Top side only
On both sides
Any side
A column of length l is fixed at both ends. The equivalent length of the column is
l/2
l/√2
l
2 l
In second type of levers,
Load is in between the fulcrum and effort
Effort is in between the fulcrum and load
Fulcrum is in between the load and effort
None of these
The condition for maximum power transmission is that the maximum tension in the flat belt should be equal to
3 Pc
Pc
Pc/3
2 Pc Where, Pc = tension in belt due to centrifugal force
In worm gears, the angle between the tangent to the pitch helix and an element of the cylinder, is known as
Helix angle
Pressure angle
Pitch lead angle
None of these
The form factor of a helical gear __________ with the increase in the helix angle.
Increases
Decreases
Remains constant
None of these
For steel, the ultimate strength in shear as compared to ultimate strength in tension is
1/2
1/3
1/4
2/3
The helix angle for double helical gears may be made up to
45°
60°
75°
90°
Lewis equation in gears is used to find the
Tensile stress in bending
Shear stress
Compressive stress in bending
Fatigue stress
Two shafts will have equal strength, if
Diameter of both the shafts is same
Angle of twist of both the shafts is same
Material of both the shafts is same
Twisting moment of both the shafts is same
When compared to the rod of the same diameter and material, a wire rope
Is less flexible
Has a much smaller load carrying capacity
Does not provide much warning before failure
Provides much greater time for remedial action before failure
In order to permit the thermal expansion/contraction of tubing, it should be
Crimped
Honed
Flared
Bent
The ratio of circumferential stress to longitudinal stress in a thin cylinder subjected to an internal pressure is
½
1
2
4
A flange coupling is used to connect two shafts
Which are perfectly aligned
Which are not in exact alignment
Have lateral misalignment
Whose axes intersect at a small angle
According to I.B.R., the efficiency of a double riveted butt joint with double cover straps of equal width should be
45 to 60 %
63 to 70 %
70 to 83 %
80 to 90 %
In hydrostatic bearings
The Oil film pressure is generated only by the rotation of the journal
The oil film is maintained by supplying oil under pressure
Do not require external supply of lubricant
Grease is used for lubrication
Whether any core is required in wire ropes
Yes
No
Sometimes
Rarely
In order to obtain bolt of uniform strength
Increase shank diameter
Increase its length
Drill an axial hole through head up to threaded portion so that shank area is equal to root area of thread
Tighten die bolt properly
When the fulcrum is in between the load and effort, the lever is said to be of
First type
Second type
Third type
Any one of these
Transverse fillet welded joints are designed for
Tensile strength
Compressive strength
Shear strength
Bending strength
For tight leakage joints, following type of thread is best suited
Metric
Buttress
Square
NPT (national pipe threads)
For applications involving high stresses in one direction only the following type of thread would be best suited
ISO metric thread
Acme thread
Square thread
Buttress thread
The objective of idler pulley in belt drive is to
Decrease the tendency of belt to slip
Increase the power transmission capacity
Increase the wrap angle and belt tension
All the above objectives