Limits and fits

Question 1

What are some of the results of guilding parts

Answer 1

Minimises number of parts
Design for ease of assembly
Design to be fool proof during assembly

Question 2

What are the benefits for DMforA

Answer 2

Shorter time to market
Smoother transition to production
Fewer components is production
Easier Assembly
Lower production costs
Higher production quality
Greater customer satisfaction

Question 3

What is another name for simultaneous engineering

Answer 3

Concurrent Engineering

Question 4

What has the to be the same between to parts for interchangabilitity

Answer 4

The size and tolerance

Question 5

Closer tolerance leads to better performance but it is….

Answer 5

More expensive

Question 6

What Tolerance should you choose

Answer 6

The largest possible tolerance without reducing the function of the part

Question 7

What is tolerance

Answer 7

an undesirable but permissible deviation from a desired dimension

Question 8

What errors cause tolerance

Answer 8

Material behaviour, temperature during process, wear of tools, human error

Question 9

What is an allowance

Answer 9

Intentional desired difference between dimensions of two meeting parts

Question 10

What percentage of parts of lie within 3 standard deviations of the nominal size

Answer 10

99.76%

Question 11

Describe clearance, interference and transition fit

Answer 11

Clearance- shaft is smaller than hole
Interference- hole is smaller than shaft
Transition- a fit that may provide either clearance or interference

Question 12

What British Standard table do we use for shaft and hole sizes

Answer 12

BS4500

Question 13

What is the fundamental deviation

Answer 13

The closest deviation to the 0 line, gives the tolerance with respect to 0

Question 14

What is a shaft based system

Answer 14

When the fundamental deviation of the shaft is always 0, i.e shaft always lies on the dotted line.

Question 15

What is a hole based system

Answer 15

When the fundamental deviation of the hole is always 0, i.e the hole always lies on the dotten line.

Question 16

What are the fundamental deviations denoted by for both holes and shafts

Answer 16

Holes use Capital letters

Shafts use lower case letters

Question 17

What letter is used for a shaft based system

Answer 17

h

Question 18

What letter is used for a hole based system

Answer 18

H

Question 19

What is the basic size of 25 H11-c11

Answer 19

25

Question 20

Is 25 H11-c11 a shaft or hole based system

Answer 20

Hole

Question 21

What is the hole tolerance grade of 25 H11-c11

Answer 21

11

Question 22

What is the shaft tolerance grade of 25 H11-c11

Answer 22

11

Question 23

When does Maximum Material condition occur

Answer 23

When hole diameter is a minimum and shaft diameter is at a maximum

Question 24

When does least material condition occur

Answer 24

when hole diameter is at a maximum and shaft diameter is at a minimum

Question 25

What is more commonly used hole based system or shaft based system and why

Answer 25

Hole based system because holes are usually only made to standard sizes

Question 26

When might a shaft based system be used

Answer 26

When fitting several parts to one shaft

Question 27

What are allowance and Tolerance functions of

Answer 27

Basic size

Question 28

How many grades do tolerances come in

Answer 28

18

Question 29

The tolerance grades are IT01, 1T0 and....

Answer 29

IT1-IT16

Question 30

Tolerances are made depending on if the part is to

Answer 30

Mate with another part and how they are to made

Question 31

What are functional and non functional parts

Answer 31

Functional parts are essential to the operation of the part so use close tolerances. Non-Functional parts are not as important and use more generous tolerances

Question 32

What is the equation for process capability index

Answer 32

PCI=T(tolerance)/6*standard deviation

Question 33

Does a hole make a difference to thermal expansion

Answer 33

No

Question 34

How is increase in allowance related to original allowance

Answer 34

Linearly

Question 35

What are shrink fits useful for

Answer 35

High torque and large axial loads

Question 36

What is the equation for allowance at maximum material condition for thermal expansion

Answer 36

Allowance at max material condition=Min hole-Max shaft+ Shaft expansion

Question 37

What is the equation for allowance at maximum material condition for thermal contraction

Answer 37

Allowance at Max material condition= Min Hole -Max shaft + Shaft contraction - Hole contraction

Question 38

What is the equation for allowance and thermal change and what are the sign convention

Answer 38

Allowance at Max material condition=Min hole-max shaft-shaft change +hole change Expansion is positive Contraction is negative

Question 39

What do the symbols stand for in the equation for shrink fitted parts

Answer 39

1=Length alpha = linear coefficient pf temperature T= temperature

Question 40

What are the symbols in the interference pressure

Answer 40

``` P= interference pressure Sigma= total diameter interference a=outer radius of inner b=outer radius of inner Eo= youngs modulus of outer Ei= youngs modulus of inner v= poisons ratio ```

Question 41

What is the equation for the torque carried by the shrink fitted

Answer 41

T=2*mu*p*pi*a^2*l

Question 42

What do the symbols in the torque equation mean

Answer 42

``` T=torque mu= co of friction p= pressure a=interference radius L=length of inference fit ```

Question 43

What percentage of parts would you expect to find within + or - 1 standard deviation of nominal size

Answer 43

68.26%

Question 44

What percentage of parts would you expect to find with + or - 2 standard deviations nominal size

Answer 44

95,46%

Question 45

What percentage of parts would you expect to find within + or - 3 standard deviations of nominal size

Answer 45

99.73%

Question 46

What is the upper deviation of the shaft.

Answer 46

Distance between max diameter and the zero line (basic size)

Question 47

What is the lower deviation of the shaft

Answer 47

Distance between min diameter and zero line (basic size)

Question 48

What is the upper deviation of the hole

Answer 48

Distance between max diameter and zero line (basic size)

Question 49

What is the lower deviation of hole

Answer 49

Distance between min diameter zero line ( basic size)

Question 50

What is the Equation for PCI

Answer 50

PCI= Tolerance/ (6x standard deviation)