A Bolt is a mechanical device which
has head on one end of a body and a thread on the other end designed for
fastening of two parts.
Bolt is inserted into
holes in assembly parts, it is mated with a tapped nut. Tension is normally induced
in the bolt to compress the assembly by rotating the nut. This may also be done
by rotation of the bolt head.
A Screw is a headed and threaded bolt
used without a nut. It is inserted into an internally tapped hole and tension
is induced by rotation of the screw head.
A Stud is a fastener with no head but
it has threads at both ends of the shank. It, like a screw, has one end those
screws into a tapped hole. A nut is used on the other end to create tension.
Major
diameter – largest diameter of thread (D)
Minor
diameter – smallest diameter of thread
Pitch
– distance between adjacent threads.
Types of nut bolts & Washers
Sl No.
|
Fastener Type
|
A
|
BOLTS
|
1
|
Hex head bolt
|
a
|
Full threaded
|
b
|
Half threaded bolts
|
2
|
Machine screws
|
3
|
Carriage bolts
|
4
|
Shoulder bolts
|
5
|
Square head bolts
|
6
|
Allen bolts (Half
threaded & full threaded)
|
7
|
Eye bolts
|
8
|
J bolts
|
9
|
U bolts
|
B
|
Screws
|
1
|
Deck screw
|
2
|
Hex lag screw
|
3
|
Self drilling screw
|
4
|
Wood screw
|
5
|
Sheet metal screw
|
C
|
Nuts
|
1
|
Hexagonal nut
|
2
|
Cap nut
|
3
|
Castle nut
|
4
|
Flange end nut
|
5
|
Hexagonal lock nut
|
6
|
Hexagonal machine
nuts
|
7
|
Keps-K lock nuts
|
8
|
Knurled thumb nuts
|
9
|
Nylon hex. Nuts
|
10
|
Slotted Hexagonal
nuts
|
11
|
Square headed nuts
|
12
|
Tee nuts
|
13
|
Wing nuts
|
D
|
Washers
|
1
|
Flat washer
(Normal)
|
2
|
Flat washer (Extra
thick)
|
3
|
Lock washer
|
4
|
Lock washer
external tooth
|
5
|
Lock washer
internal tooth
|
6
|
Square washer
|
7
|
Structural washer
|
Types of Threads:
1. British Standard Whit
Worth (B.S.W.) Threads: It is a symmetrical V thread in which the angle between the flanks
is 55°.
2. British Association
(B.A.) Thread: It is the B.S.W. thread with fine pitches having thread angle
47.5°.
3. American Standard
Threads: Included
angle is 60°.
4. Unified Standard
Thread: This
thread has rounded roots and crests with included angle 60°.
5. Square Thread: Used in power
transmission, spindles of valves etc.
6. Acme Thread: It is a modified square
thread. It is much stronger than square thread.
7. Buttress Thread: Used for transmission of
power in one direction only.
8. Metric Thread: It is an Indian standard thread similar to B.S.W, but has included
angle 60°.
Generally in all industries Metric & BSW threads are
used
Designation
of Metric size bolts:
Metric size bolts are designated based on Major diameter
& Minor diameter, pitch & thread length (Bolt length)
For Example:
M12-1.25
x 50
M
= Metric thread designation
12
= Major diameter, in millimeters
1.25
= Pitch (distance from thread to thread), in millimeters
50
= Length, in millimeters
OR
sometimes directly written as M12 X 50 mm
Designation of Inches size bolts:
Example: ¼” X 1”
Here ¼” is the major diameter of the bolt & 1” is the
length of the bolt
Note: While measuring the bolt length, head thickness is
not considered
Do you know these about valves...???
Do you know these about valves...???
How do
you identify the Metric & Inches size bolts visually??
Sl No.
|
Metric thread
|
Inches thread
|
1
|
Threads
included angle is 600
|
Threads
included angle is 550
|
2
|
Thread
crests are sharped edge
|
Threads
crests are curved (small radius is given)
|
3
|
Metric
threads are of fine having lesser pitch & measured in mm
|
Inches
threads are of coarse & measured in TPI
|
4
|
Head
size is smaller as compared to inches bolts
|
Head
size is larger
|
5
|
Diameter
of Metric size bolts is smaller for the same size of bolts
|
Diameter
of Inches size bolts is larger the same size of bolts
|
Calculation of spanner size for Metric size nut bolts
Sl.No.
|
Bolt size
|
Calculation
|
Spanner size (No.)
|
Standard spanner size (Flat both end open & Ring)
|
1
|
M3
|
3 + 1 +1 = 5 (Half of 3 =1.5 1st digit of this is to be
added with 3
|
5
|
4 X 5
|
2
|
M4
|
4 X 1.5 + 1 =7 mm
|
7
|
6 X 7
|
3
|
M5
|
5 + 2 +1 =8 mm
|
8
|
8 X 9
|
4
|
M6
|
6 X 1.5 + 1 = 10 mm
|
10
|
10 X 11
|
5
|
M7
|
7 + 3 + 1 = 10 mm
|
10
|
10 X 11
|
6
|
M8
|
8 X 1.5 + 1 =13 mm
|
13
|
12 X 13
|
7
|
M10
|
10 X 1.5 + 2 = 17 mm
|
17
|
16 X 17
|
8
|
M12
|
12 X 1.5 + 1 =19 mm
|
19
|
18 X 19
|
9
|
M14
|
14 X 1.5 + 1 = 22 mm
|
22
|
20 X 21
|
10
|
M16
|
16 X 1.5 =24 mm
|
24
|
24 X 27
|
11
|
M18
|
18 X 1.5 = 27 mm
|
27
|
24 X 27
|
12
|
M20
|
20 X 1.5 = 30 mm
|
30
|
30 X 32
|
Calculation
of spanner size for Inches size nut bolts
Sl.No.
|
Bolt size
|
Calculation
|
Spanner size (No.)
|
Standard spanner size (Flat both end open &
Ring)
|
1
|
2
soot or 1/4”
|
2 X 5
+ 1 =11 mm
|
11
|
10 X 11
|
2
|
3 soot
or 3/8”
|
3 X
5 = 15 mm
|
15
|
14 X 15
|
3
|
4 Soot
or 1/2”
|
4 X 5
=20 mm
|
20
|
20 X 21
|
4
|
5 soot
or 5/8”
|
5 X
5 + 1 =27 mm
|
27
|
24 X 27
|
5
|
6 soot
or ¾”
|
6 X 5
= 30 mm
|
30
|
30 X 32
|
6
|
7 soot
7/8”
|
7 X 5
+ 1 =36 mm
|
36
|
36 X
41
|
7
|
8 soot
1”
|
8 X 5
+ 1 = 41 mm
|
41
|
36 X
41 or 41 X 46
|
Allen bolt key size (Metric)
Allen bolt size
|
Allen key size mm
|
M3
|
2.5
|
M4
|
3
|
M5
|
4
|
M6
|
5
|
M8
|
6
|
M10
|
8
|
M12
|
10
|
M14
|
12
|
M16
|
14
|
M18
|
14
|
M20
|
17
|
M22
|
17
|
M24
|
19
|
Bolts
manufacturing process
Bolts manufacturing process involves following sub
processes
A-Wire: A long coiled steel rods of required grades are
first uncoiled & cut into required length
B-Cold forging:
C-Manufacturing of bolt head by pressing the steel into
required die
D-Heat treatment
E-Threading: Generally formed by rolling & cutting
Other general methods employed for manufacturing of nut
bolts are Machining & Forming
What heat treatment processes are carried out on nut bolts?
- Annealing
- Stress relieving
- Case hardening
- Quenching & Tempering
What properties of materials are considered while designing the nut
bolts???
- Tensile strength
- Ultimate strength
- Yield strength
- Hardness
- What are the different materials used for manufacturing of nut bolts?
Nut bolts are manufactured by different materials based
on applications, some of them are
- Carbon steel
- Stainless steel
- Alloy steel
- Brass
- Silicon Bronze
- Gun metals
Do you
know these?
- Half threaded bolts threading length = 2D + 6 mm for bolts length < 150 mm
- Half threaded bolts threading length = 2D + 12 mm for bolts length >150 mm
- Nut thickness t = 0.9 X D
- Bolt head thickness = 0.8 X D
- Plain washer internal diameter = D+1
- Plain washer outer diameter = 2D+3
- Plain washer thickness t =D/8
- Where D is the major diameter of bolt
- Spanners are made by Chromium & Vanadium alloy steel by the process forging
- The
angle of chamfer for nuts & bolts head is 300
- Aluminium & stainless steels should not be mixed while fastening. This leads to galvanic corrosion by transfer of electrons.
- Lubricant/or grease should be lapped on SS bolts before inserting into threaded holes to avoid initial friction & damages of the threads, as SS bolts are coated with thin invisible coating to prevent oxidation
- Salt water has tendency to cause fast oxidation/rusting even on SS nut bolts
- Do not mate galvanized fasteners with other (carbon steel, SS etc) to avoid thread damage as galvanized iron fasteners have thick anti-rust coatings.
Nut
bolts grades:
A-Imperial
standard grades:2,5,8 etc
- Grade 2 bolts is of low carbon steel having no any marks on its head
- Grade 5 bolts have 3 marks on its head
- Grade 8 bolts have 6 marks on its head
B-Metric
standards grades:
Generally used carbon steel nut bolts of grades 4.6, 4.8,
5.8, 8.8, 10.9 etc
Here 1st digit of grade indicates the tensile
strength of the bolt & second digit indicates the ratio of Yield strength
to ultimate strength.
For example: A bolt of grade 10.9 implies that,
Tensile strength = 10 X 100 = 1000 N/mm2
Efficiency or with standing load = 0.9 X 100 =90%
This means that, a bolt of metric grade 10.9 with stands
a load 101 kg/mm2 of (1000/9.81) & fails at 90% load (90 kg)
Stainless
steel bolts grades
Generally used nut bolts are of SS304 & SS316
materials
Grades are ,A1-50,A2-70 & A4-80
- A2-50 : Soft graded used for lower loads
- A2-70 : Austenitic steel, cold worked & tensile strength 70 X 10 = 700 Mpa
- A4-80 : Austenitic steel, cold worked & tensile strength 80 X 10 = 800 Mpa
- C4-70: Martens tic 12% Cr steel, hardened & tempered & having tensile strength 70 X 10 = 700 Mpa
Other
high temperature nut bolts grades grades:
- SA 193 grade B-7: For alloy steel bolts Quenched & Tempered
- SA 193 grade B-16: For alloy steel bolts Chromium & Vanadium
- SA 193 grade B-8 & B8M: For SS 304 carbide solution treated
- SA194 2H: For alloy steel nuts
- SA 193 & A 193 grade materials properties are same, however SA refers to the ASME grade & A refers to the ASTM grade materials
- ASTM-A 325 or A-325 -Medium carbon steel
- ASTM-A 354 Grade BB, BC & BD-Alloy steel quenched & tempered
- ASTM-A490-Alloy steel quenched & tempered
 |
| Available @ Flipcart/Amazon/Notion press |
 |
GNEY High Pressure Grease Gun 10000 PSI Lubrication 14oz Cartridges Ergonomic T-Handle with 12 Inch Flex Hose and 6 Inch Rigid Extension, 3-Way Loading (Yellow) |
