7.6 Fits & Clearances Flashcards
What does “fit” refer to in engineering?
a) The weight of the parts
b) The grade of tightness or looseness between mating parts
c) The dimensions of the parts
b) The grade of tightness or looseness between mating parts
What is a key characteristic of a clearance fit?
a) No movement is possible after assembly
b) There is always some play after assembly
c) It requires heating or cooling to assemble
b) There is always some play after assembly
How is a free-running clearance fit assembled?
a) By applying heat to the outer part
b) With light hand pressure or no force
c) Using a press to join the parts
b) With light hand pressure or no force
What is the defining characteristic of an interference fit?
a) The parts are slightly loose after assembly
b) The inner part is larger, and no movement is possible after assembly
c) It uses screws to join the parts
b) The inner part is larger, and no movement is possible after assembly
How is a driving fit achieved?
a) By forcing the parts together with a press
b) By tapping the parts together with a hammer
c) By cooling the inner part
b) By tapping the parts together with a hammer
What method is used in a force fit?
a) Parts are joined with light hand pressure
b) Parts are forced together using a press
c) Parts are heated to expand the outer member
b) Parts are forced together using a press
What is the process used in a shrink fit?
a) The outer part is heated, or the inner part is cooled to permanently join the parts
b) The parts are tapped together with a hammer
c) The parts are pressed together with a press
a) The outer part is heated, or the inner part is cooled to permanently join the parts
What does a transition fit represent?
a) A fit with significant play between parts
b) A fit between interference and clearance fits, where mating parts are almost the same size
c) A fit requiring no finishing
b) A fit between interference and clearance fits, where mating parts are almost the same size
What is required to achieve very small size differences in a transition fit?
a) Using unfinished surfaces
b) Accurate and finished surfaces
c) A larger interference
b) Accurate and finished surfaces
What is a key characteristic of a transition fit?
a) The parts are significantly different in size
b) Mating parts are almost the same size
c) The fit requires high interference
b) Mating parts are almost the same size
What are the two types of tolerances in the Newall system?
a) Nominal and actual
b) Unilateral and bi-lateral
c) Hole-based and shaft-based
b) Unilateral and bi-lateral
What is a unilateral tolerance?
a) A variation allowed in both directions
b) A variation allowed in one direction only
c) A variation that depends on the nominal size
b) A variation allowed in one direction only
What is a bi-lateral tolerance?
a) Variation allowed in both directions
b) Variation allowed in one direction only
c) Variation based on the shaft size
a) Variation allowed in both directions
What is an allowance in a fit system?
a) The variation in the size of a part
b) The intentional size difference for a proper fit between parts
c) The deviation between nominal and actual size
b) The intentional size difference for a proper fit between parts
Which fit system is more commonly used?
a) Shaft-based system
b) Hole-based system
c) Bi-lateral tolerance system
b) Hole-based system
What is the latest standard system for fits in the UK?
a) Newall system
b) BS 4500 system
c) H7-K6 system
b) BS 4500 system
What does the BS 4500 system use for fits?
a) Shaft size with varying holes
b) Holes with varying shaft sizes
c) Nominal and actual sizes
b) Holes with varying shaft sizes
What is the typical fit for H7-K6?
a) Clearance fit
b) Slight interference fit
c) Transition fit
b) Slight interference fit
What is a deviation in the context of fits and clearances?
a) The total variation allowed in size
b) The difference between the actual size and the nominal size
c) The intentional size difference for a proper fit
b) The difference between the actual size and the nominal size
What does the ovality of a hole or shaft refer to?
a) The bending of the shaft
b) The shape of the hole or shaft
c) The rotation of the shaft
b) The shape of the hole or shaft
What does the bow of a shaft indicate?
a) The shaft is bent and not straight
b) The shaft is twisted
c) The shaft has an uneven surface finish
a) The shaft is bent and not straight
What causes a shaft to become bowed?
a) Improper lubrication
b) Vibrations
c) Excessive heat during operation
b) Vibrations
What tool is used to check for a bow in a shaft?
a) Dial test indicator
b) Feeler gauge
c) Surface plate
b) Feeler gauge
How is the twist of a shaft measured?
a) By using a feeler gauge
b) With a dial test indicator mounted on a surface gauge
c) By inspecting it visually on a surface plate
b) With a dial test indicator mounted on a surface gauge
Where should a twist test be performed?
a) On a rotating machine
b) On a flat surface table
c) Inside an assembled system
b) On a flat surface table
What is used to determine if a component is within the limits for fits and clearances?
a) Measurement tables
b) Dial test indicator
c) Feeler gauge
a) Measurement tables
Which of the following are the four types of limits for wear?
a) Dimension New, Permissible Worn Dimension, Clearance New, Permissible Worn Clearance
b) Clearance New, Clearance Old, Permissible Worn Dimension, Dimension Old
c) Worn Dimension, New Clearance, Maximum Clearance, Serviceable Clearance
a) Dimension New, Permissible Worn Dimension, Clearance New, Permissible Worn Clearance
What is used to check for bow in a shaft?
a) V-blocks and dial test indicator
b) Straight edge and feeler gauge
c) Go/no-go gauge and micrometer
b) Straight edge and feeler gauge
What tools are used to check for twist in a shaft?
a) Straight edge and feeler gauge
b) V-blocks and strain gauges, DTI
c) Internal micrometers and callipers
b) V-blocks and strain gauges, DTI
What is used to measure roundness while checking for twist?
a) Dial test indicator (DTI)
b) Go/no-go gauge
c) Micrometer
a) Dial test indicator (DTI)
Which tool is used to check ovality in holes?
a) Feeler gauge
b) Go/no-go gauge, internal micrometers, or callipers
c) Micrometer or ovality gauge
b) Go/no-go gauge, internal micrometers, or callipers
What is used to check ovality in shafts?
a) feeler gauge
b) Micrometer, ovality gauge, Go/no-go gauge
c) V-blocks and strain gauges
b) Micrometer, ovality gauge, Go/no-go gauge
What does an allowance define in terms of fit?
a) The maximum size of a part
b) The classes of fit
c) The material strength
b) The classes of fit
What is the system for indicating holes and shafts in terms of fit?
a) Capital letters for shafts, lower case for holes, numbers for grade of tolerance
b) Capital letters for holes, lower case for shafts, numbers for grade of tolerance
c) Capital letters for grades, lower case for sizes, numbers for tolerance
b) Capital letters for holes, lower case for shafts, numbers for grade of tolerance
shaft and turbine wheels in a shrink fit?
a) The turbine shaft is heated, and the turbine wheels are cooled
b) The turbine shaft is cooled, and the turbine wheels are heated
c) Both the turbine shaft and wheels are heated
b) The turbine shaft is cooled, and the turbine wheels are heated
What is an example of a press fit transition fit?
a) Turbine shaft and bearings
b) Turbine shaft and turbine wheels
c) Bearing and housing
a) Turbine shaft and bearings
What causes twist and how is it measured?
a) Bending caused by load, measured by strain gauges
b) Twist caused by torsional or torque loads, measured by strain gauges
c) Shear caused by lateral loads, measured by strain gauges
b) Twist caused by torsional or torque loads, measured by strain gauges
