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Under Construction

Contents: Class & Grade | Type
(fasteners) | Terms
| Standards
| Torque
Notes | Bolt
Sizes | Tap
Drill Required | Drill
Size | Lubrication
| Links

Grade Markings:

Other
Grade markings at AmericanFastener.com

Bolt Class and Grade (Torque
specs vary - numbers below are at high end.)

Metric
Class
ISO

Inch
Grade
SAE

Type

Material

Tensile
Strength
(psi)

Torque ft-lbs. e.g. *
size-pitch
(tpi)

¼-20

3/8-16
(10mm.)

3/8-24

½-20

3.6

4.6

4.8

C.P. 50

Titanium

50,000

2024-T4

cold-formed Aluminum2

62,000

6-9

SBrass

70,000

A2-70

18-8

ASTM
302

Stainless Steel1

102,000

18-8

304

Stainless Steel

102,000

-6

-20

-22

-45

A4-80

316

316

Stainless Steel

116,000

7

21

23

47

5.8

2

Low Carbon Steel

74,000

4-6

16-21

22-24

52-63

6.8

3

Med Carbon Steel

8.8

5

Med Carbon Heat T. Steel

120,000

8-10

30-37

35-42

90-101

ASME
B16

CrMoVa Alloy Steel

125,000

8740

chrome moly

180,000

5

high tensile Titanium

120,000
160,000

13-15

17-21

64-79

9.8

6-7

Med. Carbon Temp. Steel

133,000

10-

40-

45-

100-

10.9

8

Med. Carbon Alloy Temp. Steel

150,000

12-14

45-52

50-59

120-144

12.9

Alloy Temp. Steel

170,000

"Stainless 300"

Stainless Steel special alloy from ARP

170,000

416-HT

Stainless Steel

180,000

Aermet 100

steel super-alloy3

300,000

psi - Pounds per square
inch
tpi - Threads per inch
C.P. - Commerciallly Pure
HT -
Hardened and Tempered
Temp. - Quenched and Tempered
See other terms
below

* Torques are examples. Coatings like crome, cadmium or zinc and
lubricants, inculding Loctite (which acts as a lubricant before it dries)
will affect the torque required. (higher numbers in above chart are for
zinc plated bolts). Torque tables will vary by 10-15%. The MIL-Specs (NAS
and MS) are used by the aircraft industry. The above numbers tend to be
toward the high end of the ranges. See Torque
below for more information and links to torque tables.

In the 1980's large numbers of counterfeit bolts appeared in the United
States, almost all imports. For this reason, the SAE grade markings can no
longer be trusted unless one knows exactly who made and graded the bolt.

A stronger bolt may not always be better. In some cases a bolt may be
selected to fail at a certain stress to protect a more expensive part.

Bolts are graded, designating how "hard" they are. The "harder" bolt
you choose, the higher the grade number, and the more brittle or "less
shear resistant" it becomes. Higher grades are not necessairly better
depending on the use.
The bolt material strength is determined by the
alloy and processing method (for example, cold working and heat treating.)

The American Society for Testing Materials (ASTM) is one of the
organizations which grades fastners in specification documents e.g. A193,
A194, A320. Some equivalent grades are:

ASTM

Title

A193

Standard Specification for Alloy-Steel and Stainless Steel
Bolting Materials for High-Temperature Service.

A194

Standard Specification for Carbon and Alloy Steel Nuts for Bolts
for High Pressure or High Temperature Service, or Both

A307

Standard Specification for Carbon Steel Bolts and Studs, 60 000
PSI Tensile Strength

A320

Standard Specification for Alloy-Steel and Stainless Steel
Bolting Materials for Low-Temperature Service

Grade

ASTM

Description

B7

A193

A heat-treated chromium-molybdenum steel widely used for medium
high temperature service.

B8

A193

These Chromium-Nickel (AISI 304) austenitic steel studs are used
in corrosive environments (-325¡ to 1500¡F).

B8M

A193

These Chromium-Nickel Molybdenum (AISI 316) austenitic steel
studs are used in corrosive environments (-325¡ to 1500¡F)

L7

A320

Intended for low temperature service down to minus 150¡ and has
a minimum Charpy impact value of 20 ft lb at this temperature (-150¡
to 1100¡F)

L7

A194

Heat-treated chrome-molybdenum steel nuts suitable for extreme
temperature and pressure
conditions.

MATERIALS
18-8 Stainless
Steel This is the most popular type of stainless used in the
production of fasteners. Its composition is approximately 18% Chromium and
8% Nickel, thus the name 18-8. Several grades of stainless are included in
this classification including 302, 303, 304 and 305. These all have good
strength and corrosion resistance.

316 Stainless Steel This is more corrosion resistant than 18-8,
but also more expensive. It is composed of approximately 18% Chromium and
12% Nickel with the addition of 2% to 4% Molybdenum. It also maintains its
strength at higher temperatures than 18-8.

410 Stainless Steel It has approximately 12% Chromium with no
Nickel. It is not very corrosion resistant and is magnetic, but it can be
heat treated to become harder.

Alloy 20 This alloy has approximately 20% Chromium and 34%
Nickel plus 3% to 4% Molybdenum. It is very corrosion resistant and is
especially popular when in contact with sulfuric acid.

Brass This metal is approximately 65% Copper and 35% Zinc. It offers a
good combination of strength, corrosion resistance and workability.

Nickel Copper 400 This alloy is approximately 70% Nickel and 30%
Copper. It has excellent strength and corrosion resistance and is used in
salt water marine and other chemical environments.

Titanium This has a very high strength to weight ratio, as well
as good corrosion resistance.

Inconel Registered Trademark of Inco Ltd. Composed of
approximately 77% Nickel and 15% Chromium. It offers superior strength and
good corrosion at high temperatures.

Silicon Bronze It is composed of approximately 96% Copper, 3%
Silicon, and 1% Manganese. It is more corrosion resistant and tougher than
brass. It is widely used in the electrical industry.

ISO metric fastener material strength property classes (grades) is
specified in ISO Standard 898-1. The 5 in 5.8 means nominal (minimum)
tensile ultimate strength is 5 * 100 = 500 MPa
(Megapascal); the 8 means the yield strength is 0.8 times tensile
ultimate strength or 0.8 * 500 = 400 MPa.

1. - Stainless Steel Tensil strength ranges from 74,000 -
180,000 psi.
There are two common types of stainless steel fasteners:
corrosion-resistant stainless steel, ASTM 304 (a.k.a. 18-8 †) or DIN/ISO
A2, and acid-resistant stainless steel, ASTM 316 or DIN/ISO A4. A2 is by
far the most prevalent material, and is what is normally supplied for
stainless metric fasteners.

† - 18-8 or 18/8 - Means that it contains 18% chromium and 8% nickel. A
better grade is 18/10 it provides more corrosion resistance and greater
durability.

There are three typical property classes (strengths) for in the metric
system: 50, 70, and 80. The class equals the tensile strength divided by
10. The metric property class is a dash (-) number after the alloy
designator. For example, a screw marked A2-70 is a 304 stainless steel
screw with a 700 N/mm2 tensile strength. Both alloys come in all property
classes, but A2-70 and A4-80 are the most common.

304 316 384 Austenitic Stainless Steel, Cold Worked
416-HT -
Martensitic Stainless Steel Hardened and Tempered

316 stainless steel is a higher alloyed material containing 2-3%
molybdenum, which provides improved pitting and crevice corrosion
resistant properties, especially in environments containing chlorides.

2. Aluminum 1024-T4 - 1024 specifies Alloy per Aluminum
Association series and T4 the temper.
T4 = Solution heat treated and
naturally aged to a substantially stable condition.
See: Aluminum Tempers at EngineersEdge.com
Aluminum Alloys
Typical
mechanical properties of wrought aluminum alloys
Composition
of Aluminum 2XXX Series Alloys

3. AERMET 100 is a martensitic steel super-alloy from ARP that is used for conecting rod bolts in top fuel
dragsters.

Type:
See Fasteners

Terms: (See also standards
below)
12N - National 12 Pitch
304SS = 304 Stainless
Steel
5000SA = 5000 Series Aluminum
AHSS - Advanced High-Strength
Steels
ARP - Automotive Racing Products
C.P. - Commerciallly
Pure
DP - Dual phase steel - Comprised of soft ferrite and,
depending on strength, between 20 and 70% volume of hard phases, normally
martensite.
FT - Fine thread (same as UNF)
FH - Flat Head
HH -
Hex Head
HSLA - High-strength, low alloy steel
HSS = High Strength
Steel
HT - Hardened and Tempered Quenching and tempering - A process
that is heating to about 900°C, water quenching, and tempering at
temperatures of 480 to 600°C or higher, can provide a tempered martensitic
or bainitic microstructure that results in better combinations of strength
and toughness. An increase in the carbon content to about 0.5%, usually
accompanied by an increase in manganese, allows the steels to be used in
the quenched and tempered condition.Martensitic - A DP steel with Ferrite
+ Martensite; Martensite is a highly supersaturated solid solution of
carbon in iron (iron carbide).
It is formed when steel is cooled so
rapidly that the change from austenite to pearlite is suppressed.
HX -
Hex Head
LCS = Low Carbon Steel
Martensitic steel has a much higher
ultimate tensile strength than conventional steels of similar yield
strength.
MIL - Military Spec Numbers (see MS,
NAS below)
NC - National Coarse thread pitch (same as UNC)
NF -
National Fine thread pitch (same as UNF)
NEF - National Extra Fine
thread pitch
Nm - Newton meter = 0.75 ft lb
N/mm2 -
Newtons per square millimeter.
1 N/mm2 =
145.03 pounds/in2
NS - National Special thread pitch
OH
- Oval Head
PH - Pan Head
PH - Phillips Drive
psi - Pounds per
square inch.
Rm - Ultimate tensile strength - The tensile
strength (ultimate) strength, is the stress level where the material
breaks under tension (Trying to stretch it
out).

RP0.2 - yield strength - The
yield strength is the stress level where the material yields or
permanently deforms.
SL - Slotted Drive
SHCS - Socket Head
Cap Screw
Temp. - Quenched and Tempered
Tensil Strength - see Rm
above
TRIP - Transformation Induced Plasticity Streel
tpi -
Threads per inch
MPa - Megapascal = 1 N/mm2
= 145 psi
UNC - Unified National Course thread form
Unified
National Fine thread series or just "Fine Thread (FT)"
Yield Strength -
See RP0.2 above

See: High-Strength Structural and High-Strength Low-Alloy
Steels

Standards:
ISO - International Organization for Standardization - ISO
898-1, 1999
SAE - Society of Automotive Engineers - SAE J429
ASTM - American
Society for Testing Materials
AISI - American Iron and Steel
Institute.
ASME - American Society of
Mechanical Engineers
COFS - Committee on Framing Standards of AISI
AA - Aluminum Association
Defines series (1000, 2000, ...) of Aluminum Alloys
MIL-spec - Military Specifications (AN, NAS, MS,
..)
DLA Defense Logistics Agency
AN - Army/Navy or Air
Force/Navy - World War II era hardware standards.
NAS - National
Aerospace Standards. Korea era standards systems now almost totally
duplicated by the MS system. Aerospace Fasteners List at SPS Technologies

MS - Military Standard specification. Cold war era
standards required as airplanes got more complicated.

Unfortunately, this numbering system lacks much of the logic of the
AN system it replaces. Dash numbers vary from part number to part
number and seems to bear no resemblance to size.
DIN - Deutsches
Institut fur Normung (German Standards Institute). (usually uses same
nomenclature/specs. as ISO)

See Glossaries at: bonaero.com, Defense Logistics Agency

Torque Notes:
A properly tightened
bolt is one that is stretched such that it acts like a very ridged spring
pulling mating surfaces together. There are no standard tables, because
tightening is not an accurate science.
Guidelines for
Torque:

Torque for lubricated bolts should be about 30% fo 50% less
than the unlubricated values above.

Loctite® acts as a mild lubricant before it drys. Use about 15% less
torque.

Cadmium plating - 25-30% less

Zinc plating - 10-40% more. (higher numbers in above chart
are for zinc plated)

Stainless steel fasteners have a friction coefficient about two
times the corresponding plain steel fastener. This does not mean that
stainless fasteners require double the specified torque since they
usually cannot achieve the strength of a steel fastener.

Super clean fasteners or those lubricated with light lubricants like
WD-40™ require a high torque to achieve the desired tension.

Fasteners lubricated with oil such as motor oil and the oil found on
black fasteners require a medium torque.

Fasteners lubricated with extreme pressure grease or anti-seize
paste require the least torque.

For bolts in shear reduce the values by 30-40%.

Loctite is preferred over lockwashers because lockwashers decrease
bolt clamping efficiency and Loctite serves initially as a lubricant.

Always "feel" for tightness even when using a torque wrench.

Try to avoid button head Allen/Torx bolts where any sort of torque
is required. They simply round out.

As a rule, when a bolt is installed, the nut (over a washer) should
be turned and not the bolt's head.

Unless a torque wrench is used the tendency is to undertighten large
bolts and overtighten small ones.

Bolt Torque by Grade at: Rask
Cycle, MetTec, ZeroFast.com, dansmc.com, sizes.com/tools/bolts_SAEtork.htm
Torque and Fastener Matching Information (NAS torques)
at Costal Fabrication.
Keeping it All Together - The Nuts and Bolts of
Bolting
Marine Fastners.
Recommended
Torque Spec's for Titanium Fasteners
Torque
and Screw Interchangeability at Bondhus.

Preloading accuracy

Method

By Feel

Torque Wrench

Turn-of-nut

Preload washers

Bolt elongation

Strain gauges

Accurcy

+/- 35%

+/- 25%

+/- 15%

+/- 10%

+/- 3%

+/- 1%

Source: the "Machinery's Handbook".

Sliding friction is affected by materials (like steel or aluminum on
titanium), surface roughness, bearing area, material hardness, lubrication
and so on. It takes more force to tighten a larger bolt. It takes more
force to stretch an SAE Grade 8 bolt than it does to stretch an SAE Grade
5 bolt because of the greater material strength.

Undertorque can result in unnecessary wear of nuts and
bolts as well as the parts they hold together. When insufficient pressures
are applied, uneven loads will be transmitted throughout the assembly
which may result in excessive wear or premature failure due to
fatigue.
Overtorque can be equally damaging because of failure
of the bolt or nut from overstressing the thread areas.

The basic formula Torque = K x D x P where:
K - Coefficient
of friction (nut factor). The most commonly used bolting K factors arc
0.20 for plain finished bolts, 0.22 for zinc plated bolts, and 0.10 for
waxed or highly lubricated bolts.
D - Bolts nominal diameter
(in. for in-lbs. or ft. for ft -lbs)
P = Bolt's desired tensile
load in pounds (generally 75% of yield strength - the stress level where
the material yields or permanently deforms.)
Source: ZeroFast.com

Bolt Sizes (inch/SAE to Metric)

Size Conversion

in.

mm.

1/8

3.18

5/32

3.97

3/16

4.76

7/32

5.55

1/4

6.35

9/32

7.14

5/16

7.94

3/8

9.52

7/16

11.11

1/2

12.70

9/16

14.29

5/8

15.88

11/16

17.46

3/4

19.05

13/16

20.6

See Tap
sizes.

Size

Dec.

mm.

TPI

NC

NF

Size

Dec.

mm.

TPI

#0

0.06

1.52

80

#1

0.073

1.85

64

72

#2

0.086

2.18

56

64

#3

0.099

2.51

48

56

#4

0.112

2.84

40

48

#4

0.112

2.84

36

#5 (1/8)

0.125

3.18

40

44

#6

0.138

3.51

32

40

5/32

0.156

3.97

32

#8

0.164

4.17

32

36

3/16

0.187

4.76

24

#10

0.19

4.83

24

32

#12

0.216

5.49

24

28

7/32

0.219

5.55

24

#14

0.242

6.15

20

24

Size

Dec.

mm.

TPI

NC

NF

NEF

1/4

0.25

6.35

20

28

32

5/16

0.313

7.94

18

24

3/8

0.375

9.52

16

24

7/16

0.438

11.11

14

20

28

1/2

0.50

12.70

13

20

28

9/16

0.563

14.29

12

18

24

5/8

0.625

15.88

11

18

24

3/4

.75=

19.05

10

16

Threads per inch (tpi) Thread
Series
National Coarse (NC), National Fine (NF), National Extra Fine
(NEF), National Special (NS), National 12 Pitch (12N)

Note: Pipe threads use different sizing. Some of the tubes
and lines in cars use pipe thread sizes. See pipes.

Tap Drill Sizes
See Tap Drill Size page.

Drill Sizes:
See Drill size Page.

Wrench Sizes:
Allen wrench (Hollow Set Screw) sizes

Metric:

The number before the decimal point is one-hundredth of the nominal
tensile strength of the bolt in newtons per square millimeter.

The number after the decimal point is the ratio between the nominal
yield stress and the nominal tensile strength, times ten.

8.8 is
the standard automotive grade with a tensile strength of approx
120,000psi.

Inch Grade

Marks on Head

Material

Tensile Strength

Yield Strength

N/mm2

psi

N/mm2

psi

2

none

Low Carbon Steel

510

74,000

393

57,000

5

3

Med. Carbon Heat T. Steel

827

120,000

634

92,000

8

6

Alloy Steel

1030

150,000

896

130,000

SHCS

none

Alloy Steel

1240

180,000

965

140,000

18-8

none

302 Stainless

690

100,000

448

65,000

316

none

316 Stainless

690

100,000

448

65,000

Metric Class

Marks on Head

Material

Tensile Strength

Yield Strength

N/mm2

psi

N/mm2

psi

8.8

8.8

Steel

800

116,000

640

93,000

10.9

10.9

Steel

1040

151,000

940

136,000

12.9

12.9

Alloy Steel

1220

177,000

1100

160,000

A2-70

A2-70

302 Stainless

700

102,000

450

65,000

A4-80

A4-80

316 Stainless

800

116,000

600

87,000

Source: "The Nuts
and Bolts of Bolting" by Joseph C. Dille

Lubrication:
I found a discussion on
a message board where there was no agreement on when to lubricate. Some
thought you should always oil a bolt to make it easier to remove and
another thought it would make it too easy to loosen.
When using chromed
or stainless-steel fasteners, is the appropriate use of Anti-Seize to
avoid galling and binding of the bolts when tightening (see Permatex
Loctite tech).

links:
US &
Metric Bolt Torque by Grade
Screw Finder at BobbyDyer.com
Screw
Information at search.com
Screwtypes at lara.com
Fastener Material Chart at CenturyPerformance.com
Metric
Bolt Properties Grade, Strength
Proof Loads at FullerMetric.com
Strength at AtlanticFasteners.com
ASTM, SAE AND ISO grade markings and mechanical properties
for steel fasteners at AmericanFastener.com
SAE
Standards for Bolts
CD Stud Fasteners Specifications at SunBeltWelding
Tap Drill Sizes
Corrosion Resistant Bolts at
contractors-sources.com
Aircraft Hardware
Automotive Racing Products (ARP)- Bolts
Stainles Steel fasteners with specs for Aluminum,
Titanium also at ssina.com
Fastener and Screw / Bolt Design, Formula and
Calculation at Engineers Edge
Strength Properties of Metals at EngineersEdge.com
The
Tempering of Martensite
Types of bolts and screw heads.
Fastener types.
Fasteners 101
Home Depot Special Order Fasteners at CrownBolt.com

"The
Nuts and Bolts of Bolting" by Joseph C. Dille
Fastners 101
Metallurgy for the Non-Engineer

Gardner-Westcott is a bolt manufacturer.

Pozidriv™ is a trademark of European Industrial Services
Ltd.
Pozidriv® is a registered trademarks of Phillips Screw
Co.
Torx® is a reg. trademark of Camcar-Textron Inc. USA

last updated 7 Sep
2007

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