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School > Threaded Fasteners And Locking Devices > Flashcards

Threaded Fasteners And Locking Devices Flashcards

1
Q

Threaded Fasteners include what?

A
  • Bolts
  • Screws
  • Nuts
  • Studs
  • Threaded Inserts
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2
Q

What is a Screw?

A

A bolt that mates with the internal threads of a mating piece only.

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3
Q

What is the difference between a bolt and screw.

A

Screw mating with the internal thread of a piece.

A bolt mates with a nut on the otherside of a piece.

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4
Q

What is the unthreaded part of a machine bolt called?

A

Shank

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5
Q

Name these

A

Square
Hex
Carriage
Plow

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6
Q

Descibe a Carriage Bolt

A

Mushroom shaped head with a square shoulder under the head to prevent them from rotating.

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7
Q

What is this called?

A

Elevator Bolt

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8
Q

Which screw is the most precise?

A

Cap Screws

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9
Q

What are Cap Screws made out of?

A

High tensile strength steel

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10
Q

Name these

A
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11
Q

Label these

A
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12
Q

What are the two properties of nuts that relate directly to load carrying capacity?

A
  • Nut Height
  • Wall Thickness
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13
Q

Name these

A
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14
Q

What are the designations of the external fasteners?

A
  • the nominal diameter:
    1/2 inch
  • the number of threads per inch:
    13
  • the fastener has a Unified National Course thread form:
    UNC
  • the bolts length:
    4 inches

Ex. 1/2-13 UNC x 4 LG, hexhead bolt, steel

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15
Q

What does UNC mean?

A

Unified National Coarse

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16
Q

What information do you need when identifying Imperial Thread Designations

A
  • Threads per inch
  • Nominal size of thread
  • Length
  • Product name
  • Material, Protective Finish
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17
Q

What may be omitted if not plated?

A

The Protective Finish info for Imperial Thread Designations

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18
Q

Label these

A
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19
Q

What Metric Thread Designations are there?

A
  • Nominal Diameter
  • Product Name
  • Pitch
  • Length
  • Steel Property Class or Material Identification
  • Protective Coating
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20
Q

Is there any difference between Metric and Imperial Thread Designations?

A

They are the same except Metrics Product name comes first.

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21
Q

Label these

A
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22
Q

How is a Unified Thread Designated?

A
  • Nominal Diameter
  • Number of Threads Per Inch
  • Thread Form
  • Thread Series
  • Thread Class
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23
Q

Label these

A
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24
Q

What does ISO stand for?

A

International Organization for Standardization

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25
Q

What is ISO?

Where is it used?

A
  • Is the metric thread form of Unified Form except the sizes are in mm instead of inches.
  • Used on all general purpose metric fasteners sold in canada.
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26
Q

How is ISO Designated?

A
  • A captial M
  • nominal size
  • Pitch
  • Tolerance Class
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27
Q

What is this and how is it labeled?

A
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28
Q

Which are smaller? Machine Screws or Machine Bolts

A

Machine Screws

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29
Q

Label these.

A
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30
Q

What is the standard countersink angle for Machine Screws?

A

82 degrees

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31
Q

How are Machine Screw sizes identified below 1/4 inches?

A

Number designation

From 0000 to 12

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32
Q

Label these?

A
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33
Q

Label these.

A
34
Q

Label these.

A
35
Q

How do you designate Machine Screws

A
  • The outside diameter
  • Threads Per Inch
  • Nominal Length
36
Q

Write the designation for this.

A
37
Q

Can set screws be doubled on top of one another?

A

Yes

38
Q

How are Set Screws sized?

A

0 - 12 and progressing through the bolt sizes from 1/4 inches up.

39
Q

Label these.

A
40
Q

Label these.

A
41
Q

Label these

A
42
Q

What is a good practice for set screws when applying them to a round saft?

Why?

A
  • Filing down the spot where the set screw will sit.
  • To prevent a burr from the set screw forming which would make it difficult to remove the bearing from the shaft.
43
Q

What is a good practice for set screws when key ways are not used?

A

Use two set screws 90 degrees from eachother.

44
Q

What are Studs?

A

Cylindrical shafts that are threaded on both ends

45
Q

What are two families of self threading screws?

A
  • Thread-forming screws
  • Thread-cutting screws
46
Q

What are thread forming screws used for?

A

To assemble sheet metal, plastics and soft metals, such as brass or aluminum

47
Q

What do thread forming screws do?

A

Displaces or roles the material forming a thread

48
Q

Label these

A
49
Q

Label these

A
50
Q

How do Unified Thread classes differ?

A

By tolerence and allowance

51
Q

How are Unified Thread classes expressed?

A

By a single digit number followed by a capital letter.

“A” for external threads (bolts) and “B” for internal threads (nuts)

Ex: 2B

52
Q

Are ISO metric threads classed the same way as Unified Threads?

What do they use?

A
  • No
  • ISO uses Tolerance Grades and Tolerence Positions which combine to make Tolerence Classes
53
Q

What is the Tolerance Grade?

A

A number given to indicate how great the tolerances are on both pitch diameter and the major diameter of a bolt thread. The larger the tolerances are on these two diameters the higher the tolerance grade number.

54
Q

What is Tolerance Position?

A

A letter indicating the sizes to which these two tolerances are applied.

55
Q

How do you find bolt grade on an Imperial bolt?

A

Count the number of lines on the head and add 2.

Ex: Grade 5 bolt = 3 lines + 2

56
Q

What do Grade and Class refer to on bolts?

A

Tensile strength of the bolt.

57
Q

What is Tensile strength?

A

The maximum stress that a material can sustain before it fractures.

58
Q

How do Metric fasteners indicate class?

A

With numbers on the head.

59
Q

What does a lower grade of bolt mean?

A

The lower the number the less torque you can put on the bolt.

60
Q

What is Thread Profile?

A

The view of the thread when the bolt or nut is cut in half lengthwise along its axis.

61
Q

What is Major Diameter?

A

The Largest Diameter of a screw thread. On a external thread it is the outside diameter. On an internal thread it is measured across the roots of the thread.

62
Q

What is Minor Diameter?

A

The smallest diameter of a screw thread. On an external thread it is measured aross the roots of the thread. On an internal thread it is the inside diameter.

63
Q

What is Pitch Diameter?

A

The diameter at which the thickness of the thread equals the thickness of the space between threads. It is approximately half way between the major and minor diameters.

64
Q

What is the Crest?

A

The top of the helical ridge known as the major diameter. It is the part of the thread you can touch with your finger. The root of an internal thread is on the minor diameter.

65
Q

What is Pitch?

A

The distance from a point on one thread to the same point on the next thread measured parallel to the axis of the part. Pitch of an imperial thread is expressed as 1 divided by the number of threads per inch.

66
Q

What is a Flank?

A

The angled side of a thread connecting the crest to the root.

67
Q

What is Thread Angle?

A

The included angle between the flanks of the thread.

68
Q

What is the Thread Thickness?

A

The thickness of a thread measured at the pitch diameter.

69
Q

What is Lead in a bolt?

A

The axial distance a nut advances on a screw thread after one complete turn.

70
Q

What is the Lead on a single thread bolt?

A

The same as the Pitch of the thread.

71
Q

How do you find the Lead on a mutiple thread start bolt?

A

Number of thread starts times Pitch.

72
Q

What is NPT?

A
  • National Pipe Thread
  • The American standard for pipe threads. An unbrella for different pipe threads.
73
Q

What are some National pipe thread types?

A

NPT (National Pipe Taper)
NPS (National Pipe Straight)

74
Q

What is the difference visually between NPT and NPS?

A
  • NPT threads are tapered and NPS is straight.
75
Q

Should you use teflon with NPT?

A

Yes

76
Q

Should you use Teflon with NPS?

A

No, the threads do not seal. An o-ring, ferrule or flared connection is used instead.

77
Q

Where do NPT seal?

A

On the Flanks

78
Q

Where do you find NPS?

A

On hoses, oil burners, HVAC connections….

79
Q

Where are NPT used?

A

On shower heads, barbque lines, hot water tank inlets and outlets…

80
Q

What are some cons for NPT?

A
  • Easily Deformed (not good with disassembly
  • Need to be tight
  • Tape can contaminate
  • Not great for high pressure

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