Tolerances And Fits

Question 1

What is basic hole size in terms of tolerance?

Answer 1

The hole is your size, your shaft is what is adjusted to mate parts

Question 2

Describe basic shaft size in terms of tolerances

Answer 2

Your shaft is your “basic size” and your hole is the part being adjusted

Question 3

What does unilateral tolerance mean?

Answer 3

That all tolerances and dimensions are applied in only 1 direction

Question 4

What does bilateral tolerance mean?

Answer 4

That the tolerances and dimensions are applied in both directions

Question 5

What is a class 3 fit?

Answer 5

Interference

Question 6

What causes fatigue failure?

Answer 6

Repeated stress has work hardened it

Question 7

What is the main characteristic of stainless steel?

Answer 7

Corrosion resistance

Question 8

What is the approximate percent of medium carbon steel?

Answer 8

.30-.50 percent

Question 9

What form of tolerance does +/- 0.002 represent?

Answer 9

Bilateral

Question 10

What part of a dimension is the total permissible variation in its size?

Answer 10

Tolerance

Question 11

Twisting forces put what sort of stress on a key?

Answer 11

Shear

Question 12

Where should a millwright place the bearing on a shaft if he has a choice?

Answer 12

As close to the loaded components as possible

Question 13

What is the best tool for determining radial runout?

Answer 13

Dial indicator

Question 14

Sliding fit is an example of what allowance?

Answer 14

Positive allowance

Question 15

What is Prussian blue used for?

Answer 15

Identifying contact patterns for fitting and adjusting

Question 16

What will improve with carful attention to surface finish, large fillets, runout keys, sharp edges, and closer diameter reduction ratios?

Answer 16

Fewer stress fractures

Question 17

What is tolerance?

Answer 17

Total permissible deviation of a dimension on a part

Question 18

What is the difference between the max and min limits of size called?

Answer 18

Tolerance

Question 19

What are the two systems for applying tolerances to the dimensions of a mating part called?

Answer 19

Basic hole
Basic shaft

Question 20

“The design size of the hole is basic the allowance is on the shaft” is what tolerance system?

Answer 20

Basic hole

Question 21

What is the excess material on a part called?

Answer 21

Allowance

Question 22

Define allowance

Answer 22

Excess material on a part

Question 23

“The design size of the shaft is the basic size and the allowance is in the bore of the mating part” is what tolerance system?

Answer 23

Basic shaft

Question 24

What is unilateral tolerance?

Answer 24

When all tolerance for the drawing is applied in one direction only

Question 25

What is bilateral tolerance?

Answer 25

When the tolerance for the drawing dimensions are applied in both directions.

Question 26

When the drawing tolerance dimensions go in both directions what is it called?

Answer 26

Bilateral

Question 27

When the drawing dimension tolerances go in 1 direction what is it called?

Answer 27

Unilateral tolerance

Question 28

What is another word for allowance?

Answer 28

Fit

Question 29

What does “positive allowance” refer to?

Answer 29

The minimum clearance between mating parts.

Question 30

What does “negative allowance” refer to?

Answer 30

The maximum interference between parts

Question 31

The maximum interference between parts is called what?

Answer 31

Negative allowance

Question 32

The minimum clearance between parts is called what?

Answer 32

Positive allowance

Question 33

What is the degree of fit?

Answer 33

Result specifying a tolerance to each mating part

Question 34

What are the two basic types of fit?

Answer 34

Clearance Interference

Question 35

What is clearance fit?

Answer 35

When mating parts maintain some clearance between them

Question 36

What is interference fit?

Answer 36

When there is some resistance between mating parts

Question 37

What are the 5 main classes of fit?

Answer 37

Running/sliding clearance fit Locational clearance fit Transition fit Locational interference fit Force/shrink fit

Question 38

What class of fit provides room between mating parts for lubrication?

Answer 38

Running/sliding fit

Question 39

What does running fit refer to?

Answer 39

Rotating parts

Question 40

What does sliding fit refer to?

Answer 40

To parts the slide on each other

Question 41

In sliding fit what does the clearance refer to?

Answer 41

The surface above

Question 42

How is a gib used with a dove tail?

Answer 42

To adjust the clearance between the mating parts

Question 43

Where is locational clearance fit used?

Answer 43

Normally stationary parts which can be freely assembled or disassembled

Question 44

Where is transition fits used?

Answer 44

On mating parts

Question 45

What is transition fit?

Answer 45

When the tolerance on mating parts partially overlaps so either a clearance or interference fit can occur

Question 46

Where is locational interference fits used?

Answer 46

Situations where accurate location and rigid alignment is of utmost importance

Question 47

What is locational fit NOT meant to do?

Answer 47

Transmit frictional loads from one part to another

Question 48

What is force/shrink fits?

Answer 48

When the tolerance of mating parts fully overlaps causing an interference fit

Question 49

How is the method of assembly determined? (3)

Answer 49

By the amount of interference Availability of equipment Size of the parts to be assembled

Question 50

What are the three common methods of assembling mating parts?

Answer 50

Forced fitting Shrink fitting Expansion fitting

Question 51

What is forced fitting?

Answer 51

One part is pressed onto another part

Question 52

What is shrink fitting?

Answer 52

The hub is heated to expand to allow it to be easily assembled onto the shaft

Question 53

What is expansion fitting?

Answer 53

The shaft is cooled so the part may be easily slipped onto the shaft

Question 54

What is the best method for force fitting?

Answer 54

Hydraulic press with a manual lever preferably

Question 55

What are the heat sources that can be used for shrink fitting? (6)

Answer 55

Hot water/oil bath Steam Torch Furnace Electric resistance heating Electric induction heating

Question 56

What are the 4 methods for expansion fitting

Answer 56

Industrial refrigerator Liquid air Liquid nitrogen Alcohol/dry ice

Question 57

What are the 4 main types of presses?

Answer 57

Fixed in place hydraulic Mechanical arbor Free standing hydraulic Portable hydraulic press

Question 58

What are manual pullers used for?

Answer 58

Light pulling jobs that don’t require large forces

Question 59

What are the 3 situations where a manual puller would be used

Answer 59

Pulling a component off a shaft Pulling a component out of a hole Pulling a shaft out of a component

Question 60

What are the two most common styles of manual pullers?

Answer 60

Jaw Rod

Question 61

How would you choose a manual puller?

Answer 61

The diameter of the adjusting screw should be at least 1/2 the size of the shaft

Question 62

In a hydraulic application how would you choose a puller?

Answer 62

A puller that can withstand a force exerted in tons 7-10x the diameter of the shaft in inches

Question 63

A minimum bore diameter and maximum shaft diameter is what fit?

Answer 63

Interference

Question 64

A maximum bore diameter and minimum shaft diameter is what fit?

Answer 64

Clearance fit

Question 65

Each group of fits breaks down into grades. What are the grades?

Answer 65

RC 1 - RC 9

Question 66

What is a RC 1 fit?

Answer 66

Close sliding fit

Question 67

What is RC 9 fit?

Answer 67

Loose running fit

Question 68

What type of allowance is sliding fit?

Answer 68

Positive