1. Which of the following option is not correct for ‘full interchangeability’?
a) This type of interchangeability is not feasible sometimes
b) Requires machine which can maintain low process capability
c) Machines with very high accuracy are necessary
d) For interchangeable production, this type of interchangeability is not must
Explanation: Full interchangeability is also known as universal interchangeability. Many times, universal interchangeability is not feasible because it requires machine capable of maintaining very high accuracy and high process capability.
2. What is the main use of automatic gauge in selective assembly?
a) Check accuracy of parts
b) Check parallelism of parts
c) Divide group of parts with some tolerance in smaller groups
d) Use to check errors in parts
Explanation: If parts to be assembled have normal tolerance of 0.01 mm then a gauge can be divided them into 10 different groups of 0.001 mm, this gauge is known as automatic gauge. It is for selective assembly of different parts.
3. What is the correct formula to find no. of groups in selective assembly?
a) Process capability / Tolerance desired
b) Tolerance desired / Process capability
c) Tolerance desired * Process capability
d) Tolerance desired + Process capability
Explanation: No. of groups segregated in selective assembly depends upon desired tolerance and process capability of machine. Conditions like high quality and low cost can be achieved by selective assembly technique.
4. What is a limit system?
a) Series of tolerances
b) Series of fits
c) Series of clearances
d) Series of limits
Explanation: Limit system is a series of tolerances arranged to suit a specific range of size. By this, limits of size are selected and given to mating parts to ensure specific classes of fit.
5. Which of the following is correct for selective assembly?
a) Not suitable for industrial purposes
b) Cost increases due to automatic gauging
c) Wastage is high due to selective selection
d) This method is followed in ball and roller bearing units
Explanation: Selective assembly technique is widely used in industries. It is followed in automobile, air craft industries and in ball and roller bearing units. Tolerances desired in these industries are very narrow.
6. What does ‘50’ represents in 50H8/g7?
a) Basic size
b) Actual size
c) Maximum limit of size
d) Minimum limit of size
Explanation: 50 represent the basic size of the hole and shaft. H and g are the positions of tolerance zone with respect to zero line for hole and shaft respectively. 8 and 7 are the tolerance size.
7. What is ‘Go limit’?
a) Lower limit of shaft and upper limit of hole
b) Lower limit of shaft and hole
c) Upper limit of shaft and lower limit of a hole
d) Upper limit of shaft and hole
Explanation: ‘Go limit’ deals with upper limit of shaft and lower limit of hole and refers to the maximum material condition. ‘No-go’ limits deals with lower limit of shaft and upper limit of hole and refers to the minimum material condition.
8. Which of the following is incorrect regarding terminology?
a) Grades of tolerances decides manufacture’s accuracy
b) For any basic size there are 20 different shafts
c) Line of zero deviation is known as zero line
d) Tolerance has no sign
Explanation: For any basic size, there are 25 different shafts. These are designated by small letters from a to zc. Each shaft has 20 tolerance grades. Tolerance is the algebraic difference between lower and upper deviation.
9. What is the actual deviation?
a) Algebraic sum between actual size and corresponding basic size
b) Algebraic difference between actual and corresponding basic size
c) Average of actual and basic size
d) Algebraic difference between upper and lower deviation
Explanation: Algebraic difference between a size and a corresponding basic size is called deviation. Limit deviations are upper and lower deviations. Algebraic difference of actual size with basic size is called actual deviation.
10. What is the condition for a positive upper deviation?
a) Maximum limit of size > basic size
b) Maximum limit of size is < basic size
c) Minimum limit of size > basic size
d) Maximum limit of size < basic size
Explanation: Upper deviation is positive when maximum limit of size > its basic size and negative when maximum limits size < basic size. For lowers deviations, it is a positive quantity when minimum limit size is more than its corresponding basic size.