Threads And Fasteners Flashcards

1
Q

What are the main purposes of a screw thread?

A

To transmit power and increase force

Control movement

Convey material

Hold parts together

Form a pressure tight joint

For measuring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does pitch refer to?

A

Distance from a point on a screw thread to a corresponding point on the next thread. Measured parallel to its axis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is major diameter

A

Largest diameter of screw head

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is minor diameter?

A

Smallest diameter of the thread

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is lead?

A

The distance a thread advances in one turn.

Single start screw lead is same as pitch

Two start screw the lead is twice the pitch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is crest?

A

The top surface joining adjacent sides of the threads.

Can be flat, rounded, or sharp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is root?

A

Root is the bottom surface joining to adjacent sides.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the flank?

A

Flank or side is the surface of the thread connecting the crest of the root.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is thread angle?

A

Thread angle is is formed by the sides or flanks of a screw thread.

Most fasteners have a 60degree thread angle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

When a thread winds clockwise and appears to be going away from you it is?

A

A right hand thread

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What percent of load is taken by the first thread next to the washer and the second thread?

A

50 % for the first thread

25% for the second thread

The rest of the thread share the remaining 25%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What letter is internal thread?

A

B is internal thread

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

3/4”-10unc-2Ax1 1/2

A
3/4 = nominal diameter 
10 = threads per inch 
UNC = thread style (unified national course
2= class of fit 
A = external thread
1 1/2 = length
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a class 1 fit?

A

Maximum looseness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a class 2 fit?

A

An average fit.

Everyday nuts bolts and cap screws

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is class 3 fit?

A

No looseness in mating threads.

Cannot be assembled by hand.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a class 4 fit?

A

Precision threads

Usually used for precision tools and instruments such as micrometers.

18
Q

What is a class 5/6 fit?

A

The most precise and accurate threads.

Used for extremely precise tools and high vibration conditions.

19
Q

What are the four designations of ANT(American national thread)?

A

National course(Nc)

National fine (NF)

National extra fine (NEF)

National special (NS)

20
Q

What are the 4 designations for unified screw thread?

A

Unified national course (UNC)

Unified national fine (UNF)

Unified national extra fine (UNEF)

Unified national special (UNS)

21
Q

What is a constant pitch series?

A

Threads in this series have same pitch for all diameters

This series is a continuation of the extra fine thread series.

22
Q

What is an acne thread used for?

A

Mainly used for an adjusting and positioning screw.

It has a 29degree included angle

23
Q

What is the taper of a pipe thread?

A

3/4 inch per foot

24
Q

M8x1.25x50mm means?

A
M = metric 
8 = nominal size 
1.25 = the pitch in mm
50mm = length
25
What are the 3 ways fasteners are classified?
Tensile strength Design or shape Size and thread pitch
26
A grade 5 bolt has how many lines?
3
27
A grade 8 bolt has how many lines
5
28
L9 bolts are high strength. How many lines do they have?
9
29
A metric class 8.8 is comparable to what imperial bolt?
Grade 5 @ 830 mpa
30
A metric class 10.9 is comparable to a what class imperial bolt?
Grade 8 @ 1040 mps
31
A hexagonal nut is used for?
General purpose
32
What are the slots for on a slotted hex nut?
To accept a cotter pin
33
What is a stover nut and how does it work?
A stover nut is a self locking nut that have the top inner surfaces bent inward. When the top of the bolt is threaded onto the bolt it creates resistance
34
What is a nylock
A self locking nut that uses nylon that applies pressure to the bolt.
35
How do you find major diameter of a machine screw?
Multiply the screw number by .013 and add .060
36
What are taper pins used for?
Taper pins are used to fasten machinery parts that need a precise fit. Taper ratio is 1:48 (1/4” per foot)
37
How does a spring pin work?
Spring pins are made slight larger with a slit cut into them. They depress when pushed into a hole and crest pressure against the hole
38
What are the 3 types of convenience pins?
Spring locking pins Straight leg pin Quick lock pin
39
Nominal diameter - pitch =‘s?
Tap drill size (TDS)
40
What are the 3 ways fasteners fail during installations?
Shank may break Strip external threads Strip internal threads
41
Tensile forces can be classed as?
Elastic limit - amount a fastener can stretched and still return to its original length Yield point - where the fastener begins to take a permanent set. Ultimate tensile strength - the failure or breaking point.