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Millwright Block 2 (harmonized) NS > Keys And Keyseats > Flashcards

Keys And Keyseats Flashcards

1
Q

Why is the fit of shafts and their attachments imported to the machine?

A

The fit is crucial to smooth running and long life of the machine
Poor fit = poor life

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2
Q

What are Keys and keyseats (keyways) used for? (2)

A

To locate parts precisely
To positively join parts together

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3
Q

A __________ is an axial (longitudinal) groove accurately cut (machined) into the shaft or hub to retain a key

A

Keyseat (keyway)

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4
Q

What dictates the key choice?

A

-shaft size
-hub diameter
-mounting style
- torque exerted
-type of material
-intended use
-life of installation (permanent or semi)
-engineering specs

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5
Q

What is typical key stock material?

A

Low to medium carbon steel
Ex: 1020

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6
Q

What does AISI stand for?

A

American iron and steel institute

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7
Q

What is the difference of using cold finished square bar stock such as 1018 vs typical key stock 1020?

A

Square bar stock is made to a minus tolerance

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8
Q

Describe parallel keys

A

The top and bottom are parallel
The sides are parallel

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9
Q

What is the significance to key stock tolerances

A

Manufactured to a plus tolerance

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10
Q

What is the most common form of parallel keys?

A

Square or flat (rectangular) keys

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11
Q

What shafts can square and rectangular keys be used on?

A

All sized shafts

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12
Q

When would you use square keys instead of rectangular keys?

A

When the shaft diameter is up to or under 165mm (6 1/2 inches)

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13
Q

If a shaft diameter is 190.5mm (7.5 inches) would you use square or rectangular keys?

A

Rectangular

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14
Q

If your shaft keyseat is a different width than your hub keyseat what key would you use?

A

Step key (offset key)

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15
Q

Describe a saddle key

A

Shaped to fit the curve of the shaft but fitted to sit in the keyseat of the hub

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16
Q

If a key is square or rectangular that has both sides rounded what is it called?

A

Boxed or blind key

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17
Q

What key is this?

A

Box or blinded key

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18
Q

What key is shown in the picture?

A

Stepped or offset key

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19
Q

When is a sunk key used?

A

Where the mating machine components restrict access to the key on both sides

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20
Q

What is the significance to a feather key?

A

Permits movement of two parts either in operation or during assembly

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21
Q

What are the two types of feather keys?

A

Fixed feather key
Sliding feather key

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22
Q

Describe a gib headed key

A

A key with an enlarged head on one end

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23
Q

What is the purpose of a gib headed key?

A

Allows for quick extraction for parts that are removed frequently

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24
Q

What type of key is this?

A

Gib headed key

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25
Q

What is the standard taper for tapered keys?

A

1 in 96
1/8” in 12”

Metric is 1 in 100

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26
Q

What is a woodruff key?

A

A semi circular key but is also available with a flattened bottom

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27
Q

At what size are woodruff keys available with a flattened bottom?

A

1 1/2 inch

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28
Q

With woodruff keys which way does the semi circular sit?

A

Towards the shaft

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29
Q

What are the two ways a parallel keyseat may be cut?

A

Open
Boxed

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30
Q

If a keyseat is at the end of the shaft is is considered ____________

A

Open

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31
Q

If a keyseat is anywhere along the shaft it is considered to be _____________

A

Boxed

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32
Q

How is the shape of the end of the keyseat determined?

A

By the type of milling cutter used to cut the groove

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33
Q

A horizontal milling cutter produce what type of keyseat end?

A

Runout or sled runner

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34
Q

What type of keyseat end does an end mill produce?

A

Profile keyseat (straight)

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35
Q

What is the maximum tolerance for cutting an offset alignment keyseat?

A

0.25mm (0.010”)

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36
Q

What is the maximum tolerance for cutting an angular misalignment keyseat in a distance of 100mm (4”)

A

0.10mm (0.002”)

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37
Q

Is a set screw required to secure a woodruff key?

A

No

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38
Q

When is the location of the keyseat critical?

A

When strength or timing of the attachment is important

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39
Q

How deep are parallel keyseats cut in the bore?

A

Deep enough to accommodate 1/2 the height of the key plus clearance

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40
Q

When is a tapered keyseat used?

A

When using a tapered key

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41
Q

When should a tapered keyseat be longer than the key?

A

When the keyseat is NOT located at the end of the shaft

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42
Q

Who sets the standards for keys and their keyseats in relation to nominal shaft diameter?

A

ANSI
(American National Steel Institute)

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43
Q

What portable device is used to cut keyseats in the field?

A

Portable keyseat cutter

44
Q

When picking your end mill to produce a keyseat to the correct dimensions you should __________________________

A

Cut first with the next smallest size end mill

45
Q

How much material should you leave in a keyseat for finishing?

A

0.25mm (0.010”)

46
Q

What is the size difference between teeth of a broach?

A

0.07mm (0.003”)

47
Q

Each pass of a broach cuts to a depth of _________

A

1/16”

48
Q

How do you adjust the depth of a cut with a broach?

A

By using shims

49
Q

The degree of interference or clearance that a key has in relation to that shaft and hub is recognized as what?

A

The class of fit

50
Q

How many classes of fit are there in terms of clearance of interference of a key?

A

3

51
Q

What is the characteristics of a class 1 fit key?

A

Clearance fit
Relatively free fitting

52
Q

How do you obtain a class 1 key fit with a parallel key?

A

Standard square bar stock and key seat tolerance

53
Q

How do you obtain a class 2 key fit with a parallel key?

A

Key stock and Standard keyseat tolerances

54
Q

What is a class 2 key seat fit described as?

A

Relatively tight fit with slight interference

55
Q

How do you obtain a class 3 key fit with a parallel key?

A

Key stock and precision cut keyseats

56
Q

How would you describe a class 3 key fit?

A

Interference fit (no relative movement)

57
Q

What are the two main methods to secure a key to the keyseat?

A

Adhesive
Set screws

58
Q

When should adhesives NOT be used to adhere a key to a keyseat?

A

When temperatures are above 93 Celsius

59
Q

What are the 6 types of set screw points?

A

Cup
Flat
Cone
Oval
Half dog
Full dog

60
Q

What is the benefit of using a cup point set screw?

A

Sharp edges dig into the metal of the shaft giving a very effective locking action

61
Q

Where should a cup point set screw be used?

A

Where vibration is a concern and shaft marring isn’t an issue

62
Q

What is the disadvantage of using a cup point set screw

A

It marks up the shaft

63
Q

When are flat point set screws used?

A

When the shafts needs to remain not damaged at the screw point

64
Q

What is the benefit of using a cone point set screw?

A

Similar to the cup but more precise

65
Q

When are oval point set screws used?

A

When the part needs to be adjusted frequently

66
Q

What is unique about the half dog point set screw?

A

Allows lengthwise movement but prevents rotational movement

67
Q

How does the half dog set screw work?

A

Engages directly in slots milled longitudinally in a shaft to allow specific movement

68
Q

What can help ensure the maximum thrust is exerted on the shaft from a set screw?

A

Lubrication

69
Q

If you are adding more than one set screw where should you place them?

A

90 degrees to each other

70
Q

How can a set screw be locked in place?

A

Using a socket locking screw

71
Q

When should set screws be replaced? (3)

A

Major overhauls
Signs of wear
Every time if stainless steel

72
Q

How do you remove a gib headed key?

A

Fox wedge(s)

73
Q

What are the 4 methods to removing a parallel key?

A

Slide hammer
Vice grips
Key drift
Welding a rod to pull it out

74
Q

What is the rule of thumb for finding the width of a key?

A

1/4 the diameter of the shaft

75
Q

What is the rule of thumb for finding the diameter of a key?

A

Equal to the shaft diameter

76
Q

What is the rule of thumb for finding the woodruff key sizes?

A

WD40

77
Q

What is the size of a #406 woodruff key?

A

WD 40
4/32
06/8

78
Q

Where are woodruff keys typically used?

A

Tapered shafts
Light duty work

79
Q

How much of the height of a sunk key is in the keyseat (shaft)

A

2/3 of the key

80
Q

How much of the height of a sunk key is in the keyway (bore)

A

1/3

81
Q

When cutting your tapered keyseat where is it cut?

A

On the hub side

82
Q

Where is the keyseat cut at an angle for tapered keys?

A

Hub

83
Q

What type of setscrew has the best grip and tends to stay tight?

A

Cup point

84
Q

Why do we chamfer all edges of parallel keys?

A

To clear the radius of the keyseat corners

85
Q

What is the taper on an inch dimension tapered key?

A

1/8” per foot

86
Q

Where are square keys used?

A

Most applications on shafts under 6.5”

87
Q

What thickness key would you use on a 2” shaft under heavy load?

A

1/2”

88
Q

When should a fixed feather key be used?

A

When you need to lock rotation but move axially

89
Q

What type of keyseat can you cut with an end mill?

A

Profile key

90
Q

What are splines?

A

External grooves and lands that manufacturers machine on a shaft to match with internal grooves and lands in a gear, collar, sleeve, or coupling

91
Q

Where should you NOT use tapered gib head keys?

A

With cast iron hubs

92
Q

What do taper pins require?

A

Tapered reamer

93
Q

When are pin hubs normally drilled?

A

On assembly

94
Q

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

A

Tolerance

95
Q

To reduce stress turned down sections of a shaft should have what 2 things?

A

No more than 1.5:1 ratio
Large as possible fillet

96
Q

What causes fatigue failure?

A

Repeated stress has work hardened it

97
Q

Where would you measure axial runout?

A

The face of the attachment or hub

98
Q

What is a class 1 key fitting?

A

Clearance fit

99
Q

What is a class 2 key fitting

A

Tight fit

100
Q

What is a class 3 fit?

A

Interference

101
Q

What is a positive allowance?

A

Clearance fit

102
Q

What is a negative allowance?

A

Interference fit

103
Q

Where are rectangular keys used?

A

Large, hollow shafts, or thin diameter hubs

104
Q

What would you do if a broach did NOT cut a keyway to full depth?

A

Use a shim under the broach

105
Q

What sort of keyseat is cut with a horizontal mill and a side milling cutter?

A

Sled runner keyseat

Millwright Block 2 (harmonized) NS (17 decks)

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