Fastener TrainingHex Head Cap ScrewHex NutsFlat Washers

Presented byKevin ConnollyApplications Engineerkfc@earnestmachine.com

Fastener Terms and Abbreviations

Below are three ways of describing the same fastener:1. 1/4 – 20 UNC Class 2A x 1 Hex Head Cap Screw per ASME B18.2.1,

Grade 5 per SAE J429, Zinc/Clear plated per ASTM B633 2. 1/4 - 20 x 1 Hex Cap Screw, Gr 5, Zn3. 1/4 x 1 Hex Bolt, NC, 5, Z

Metric Fasteners: M10 x 50 Hex Bolt, Property Class 8.8, YWhat it means: They want a 10mm diameter hex head cap screw with a coarse thread (1.5mm) that is made from a property class 8.8 steel and is

plated zinc with yellow chromate.

The last three pages of this slide show contains a list of common abbreviations used when customers describe fasteners.

Bolts Screws (must be assembled with a nut) (can be assembled by head or with a nut)

Grade 8Regual Hex Head Cap Screw

Grade A490Heavy HexCap Screw

Thread Length =

2 x Diameter + 1/4”

(for lengths up to 6”)

Dimensions for Hex and Heavy Hex Cap Screws specified by ASME/ANSI B18.2.1

Screw Sizes Coarse and Fine Threads

Inch SizeCoarse (UNC)

Fine (UNF)

Decimal Closest Decimal

Equivalent Metric Size Conversion

1/4 - 20 .250" M6 x 1.0 .236"- 28 x 0.75

5/16 - 18 .3125" M8 x 1.25x 1.0

.315"- 24

3/8 - 16 .375" M10 x 1.5 .394"- 24 x 1.25

7/16 - 14 .4375"- 20

1/2 - 13 .500" M12 x 1.75 .472"- 20 x 1.25

9/16 - 12 .5625" M14 x 2.0x 1.5

.551"- 18

5/8 - 11 .625" M16 x 2.0x 1.5

.630"- 18

M18 x 2.5x 1.5

.709"

3/4 - 10 .750"- 16

M20 x 2.5x 1.5

.787"

7/8 - 9 .875" M22 x 2.5 .866"- 14 x 1.5

1 – 8 UNC1.000" M24 x 3.0

x 2.0

.945"- 12 UNF- 14 UNS1 1/8 - 7 1.125"

- 12

M30 x 3.5x 2.0

1.181"

1 1/4 - 7 1.250"- 12

M36 x 4.0x 3.0

1.417

Ultimate Tensile Strength (UTS)Force required to cause failure in cap screw in axial direction.

Grade 1 60,000 psi minimumGrade 2 74,000 psi minimum Property Class 4.6 400 MPa min Grade 5 120,000 psi minimum Property Class 8.8 830 MPa minGrade 8 150,000 psi minimum Property Class 10.9 1040 MPa min Grade 9 180,000 psi minimum Property Class 12.9 1220 MPa min

If we had a bar that was heat treated to a Grade 8 strength level and the bar is one square inch in diameter, it would take 150,000 pounds to pull the bar apart.

Inch Cap Screw Strength Designations

Inch

StrengthDesignations

Tensile Strength

(min)

Material Properties

Bowmalloy (Grade 9)

180,000 psi Alloy Steel Highest StrengthExcellent Wear and Abrasion Resistance

SAE Grades

Grade 8 150,000 psi Alloy Steel High Strength and Toughness

Grade 5 120,000 psi to 90,000 psi

Carbon Steel Medium Strength(standard)

Grade 2Grade 1

74,000 psi60,000 psi

Carbon Steel Low Strength

ASTM Grades

A490 150,000 psi Alloy Steel High Strength and Toughness

A325 120,000 psi Carbon Steel Medium Strength

B7 (A193)125,000 psi Alloy Steel Medium Strength

with Excellent Toughness

A307 60,000 psi Carbon Steel Low Strength

Metric Cap Screw Strength Levels

Metric Strength

Designations

Tensile Strength (min)

Material Properties

Property Class 12.9 1220 MPa(177,000 psi)

Alloy Steel Highest StrengthExcellent Wear and Abrasion Resistance

Property Class 10.9 1040 MPa(150,800 psi)

Alloy Steel High Strength and Toughness

Property Class 8.8 830 MPa(120,350 psi)

Carbon Steel Medium Strength(standard)

Property Class 4.6 400 MPa(58,000 psi)

Carbon Steel Low Strength

Grade 1 & 2

SAE Grades

A307 Grade A Grade B7 A325 A490

ASTM Grades

Grade 9

Proprietary Grade

Grade 8Grade 5

Head Markings – Inch & Metric

Metric Grades

Property Class 4.6 Property Class 8.8 Property Class 10.9 Property Class 12.9

Socket Products

Socket products do not come in different grades like hex head cap screws

Counterbore Screw

Tensile Strength :Diameters 1/4 to 1/2” 180,000 psi minDiameters above 1/2” 170,000 psi min

Set screws used to hold shafts in place

12 Point Flange Screws are used to replace standard socket heads

Finished Hex Jam Nut

Finished Full Hex Nut

Finished Thick Hex Nut

Hex Hi Nut

Heavy Hex Jam Nut

Heavy Full Hex Nut

Coupling Nut

Double Chamfered Nut Washer Faced Nut

chamfered corners

top ischamfered

bottom haswasher face

Diameters 5/8 and smaller must be doulbe chamfered

Diameters larger than 5/8 may be washer faced ordoulbe chamfered

WAF

Thickness

Hex Nuts

Hex Nuts Heavy Hex Nuts

Grade

Hardness Proof Load Strength (psi)

Grade

Hardness Proof Load Strength (psi)

2 Rc 32 max

(not defined)

A

Rb 68 / Rc 32 UNC UNF 100,000 90,000

5

Rc 32 max Dia.

14/ to 1 1 1/8 to 1 1/2

UNC 120,000 105,000

UNF 109,000 94,000

5

Rc 32 max

Dia

1/4 to 1 1 1/8 to 1

1/2

UNC 133,000 116,000

UNF 120,000 105,000

C

Rb 78 / Rc 38

UNC UNF 144,000 (not defined)

8

Dia

1/4 to 5/8 Rc 24/32 3/4 to 1 Rc 26/34 1 1/8 to 1 1/2 Rc 26/36

150,000 8

Dia 1/4 to 5/8 Rc 24/32 3/4 to 1 Rc 26/34 1 1/8 to 1 1/2 Rc 26/36

UNC UNF

165,000 150,000

9 Rc 30/38 180,000

2H 1/4 to 1 1/2 Rc 24/35 above 1 1/2 Rb 95/Rc 35 175,000

Hex Flange Nut

Hex Nuts Heavy Hex Nuts

Grade

Hardness Proof Load Strength (psi)

Grade

Hardness Proof Load Strength (psi)

2 Rc 32 max

(not defined)

A

Rb 68 / Rc 32 UNC UNF 100,000 90,000

5

Rc 32 max Dia.

14/ to 1 1 1/8 to 1 1/2

UNC 120,000 105,000

UNF 109,000 94,000

5

Rc 32 max

Dia

1/4 to 1 1 1/8 to 1

1/2

UNC 133,000 116,000

UNF 120,000 105,000

8

Dia

1/4 to 5/8 Rc 24/32 3/4 to 1 Rc 26/34 1 1/8 to 1 1/2 Rc 26/36

150,000

C

Rb 78 / Rc 38

UNC UNF 144,000 (not defined)

8

Dia 1/4 to 5/8 Rc 24/32 3/4 to 1 Rc 26/34 1 1/8 to 1 1/2 Rc 26/36

UNC UNF

165,000 150,000

9 Rc 30/38 180,000 2H 1/4 to 1 1/2 Rc 24/35 above 1 1/2 Rb 95/Rc 35 175,000

Metric Hex Nuts Property

Class Hardness Proof Load

Strength (equivalent English

Units) 6 Rb 70/Rc 32 680 MPa 98,600 psi 8 M6 to M16 Rb 80/Rc 32

M16 > Rc23 / Rc 35 880 MPa 920 MPa

127,600 psi 133,400 psi

10 Rc 26 / 36 M4 to M10 1040 MPa M12 > 1060 MPa

150,800 psi 153,700 psi

Castle NutThick Slotted Hex Nut

Finished Slotted Hex Nut

Slotted Hex Jam Nut

Heavy Full Hex Nut

Slotted Nuts

Nut installed at point where hole is visible

Legs of cotter pin bent open to hold nut in place

1/4 thru 1 UNC Over 1” UNC 1/4 thru 1 UNF Over 1 UNF

96,000 psi min 87,000 psi min 84,000 psi min 75,000 psi min

Grade 5 Hex Slotted Nuts

1/4 thru 1 1/2

120,000 psi min

Grade 8 Hex Slotted Nuts

* *

* *

2H

Old SAE Marking

ASTM marking

SAE markings

Hex Nut Grade Markings

Lock NutsAll Metal Lock Nuts Nylon Insert Lock Nuts

Flange Lock Nuts

IFI Grade For Sizes Proof Load Strength

Max Grade of Cap Screw to be used with

Grade A #4 to 1 1/2 (UNC & UNF) 90,000 Grade 2

Grade B #4 to 1” (UNC & UNF)1 1/8 to 1 1/2” (UNC & UNF)

120,000105,000 Grade 5

Grade C #4 to 1 1/2 (UNC & UNF) 150,000 Grade 8

Grade F 1/4 thru 3/4 120,000 Grade 5Grade G 1/4 thru 5/8 150,000 Grade 8

SAE Grade For Sizes Proof Load Strength

Max Grade of Cap Screw to be used with

Grade 2 1/4 to 1 1/2 (not defined) Grade 2

Grade 5

1/4 to 1” (UNC)1/4 to 1” (UNF)

1 1/8 to 1 1/2 (UNC)1 1/8 to 1 1/2 (UNF)

120,000109,000105,00094,000

Grade 5

Grade 8 1/4 to 1 1/2 150,000 Grade 8

USS Washer(Wide Sereis)

SAE Washer(Narrow Series)

F436 Washer Thick Washer

Fender Washer(Widest Style)

Flat Washers

Flat Washers are not graded.

There is no grade 8 or grade 5 washer

Three Types• Carbon Steel (aka, low carbon steel or steel)

For Grade 1, 2 or 5• Case hardened steel

For Grade 5• Through Hardened

For Grade 8

1 1/2 x Dia

Blind (or Tapped)Hole Assembly

Nut and Bolt Assembly

Gasketed Joint Assembly

Gasket

Steel

Steel

Aluminum

Copper

Clamping Soft Metals

Types of Applications

Zinc Yellow

Hot Dip Galvanized

Zinc Plated (Zinc/Clear)

Platings & Coatings

Furnace Black (Plain)

(black oxide from heat treatment)Plain

(non-heat treated)

Corrosion Protection

Coating Salt Spray Hours

Hot Dip Galvanized 240 hrs

Zinc Yellow 96 hrs

Zinc Plated (Zn/Clear) 72 hrs

Furnace Black 4 hrs

Plain 0 hrs

Torque Calculations for FastenersStandard industry practice for calculating torque for a fastener assembly is to use the formula

Torque = Clamp Load x Diameter x Friction Factor / 12 (T=PxDxK/12)

The desired clamp load is usually based on 75% of the Yield Strength (or Proof Load Strength) of the threaded fastener usedin the assembly (the nut used should be compatible with the strength of the threaded component). The Friction Factor is based on the surface finish of the two components being assembled. If both components have a plain steel finish then the Friction Factor(K) is assumed to be .20. The use of lubricants on the threads can reduce the Friction Factor to .12 and the addition of platings that do not slide across each other well can increase the Friction Factor to .22 (for zinc plating).The table listed below shows the recommended clamp loads for Grade 2, 5 and 8 assemblies (per SAE J429 and J995).

Recommended Clamp Load(based on 75% of Cap Screws Proof Load)

Recommended Torque(for plain finish assemblies)

Diameter TPI Area StressGrade 2

Clamp Load(lbs)

Grade 5Clamp Load

(lbs)

Grade 8Clamp Load

(lbs)

Gr 2TorqueFt-Lbs

Gr 5TorqueFt-Lbs

Gr 8TorqueFt-Lbs

Dry(K=.20)

Lubed(K=.15)

Dry(K=.20)

Lubed(K=.15)

Dry(K=.20)

Lubed(K=.15)

1/4 20 0.0318 1312 2027 2862 5 4 8 6 12 9

28 0.0364 1502 2321 3276 6 5 10 7 14 10

5/1618 0.0524 2162 3341 4716 11 8 17 13 25 18

24 0.058 2393 3698 5220 12 9 19 14 27 20

3/8 16 0.0775 3197 4941 6975 20 15 31 23 44 33

24 0.0878 3622 5597 7902 23 17 35 26 49 37

7/1614 0.1063 4385 6777 9567 32 24 49 37 70 52

20 0.1187 4896 7567 10683 36 27 55 41 78 58

1/2 13 0.1419 5853 9046 12771 49 37 75 57 106 80

20 0.1599 6596 10194 14391 55 41 85 64 120 90

9/1612 0.182 7508 11603 16380 70 53 109 82 154 115

18 0.203 8374 12941 18270 79 59 121 91 171 128

5/8 11 0.226 9323 14408 20340 97 73 150 113 212 159

18 0.256 10560 16320 23040 110 83 170 128 240 180

3/4 10 0.334 13778 21293 30060 172 129 266 200 376 282

16 0.373 15386 23779 33570 192 144 297 223 420 315

7/8 9 0.462 11435 29453 41580 167 125 430 322 606 455

14 0.509 12598 32449 45810 184 138 473 355 668 501

1 8 0.606 14999 38633 54540 250 187 644 483 909 682

14 0.68 16805 43286 61110 280 210 721 541 1019 764

1 1/8 7 0.763 18884 42347 68670 354 266 794 595 1288 966

12 0.856 21186 47508 77040 397 298 891 668 1445 1083

1 1/4 7 0.969 23983 53780 87210 500 375 1120 840 1817 1363

12 1.073 26557 59552 96570 553 415 1241 930 2012 1509

All material included in this table is for reference purposes only and its use by anyone is entirely voluntary. Reliance on its contents by anyone for any purpose is at the sole risk of that person. Earnest is not responsible for any loss, claim or damage arising therefrom. In developing these tables, Earnest has made a determined effort to present the contents accurately.

• Common Abbreviations used with Fasteners• 18-8 Stainless Steel with 18% Chrome and 8% Nickel• 2, 5 or 8 Strength grade of screw or nut• 2A (3A) Class of Thread Fit for inch screws • 2B (3B) Class of Thread fit for inch nuts• 2H Nut strength level designation (ASTM A194 Grade 2H Heavy Hex Nut)• 6g Class of thread fit for metric screws• 6H Class of thread fit for metric nuts• A325 Heavy Hex Structural Bolt (ASTM A325), similar to Grade 5• A490 Heavy Hex Structural Bolt ASTM A490), similar to Grade 8• A574 Strength grade for Socket head cap screws (ASTM A574)• AISI American Iron and Steel Institute, specifies chemical composition of steels• ANSI American National Standards Institute• AS Alloy Steel• ASME American Society of Mechanical Engineers• ASTM American Society for Testing and Materials• B When followed by a number (ex B-90) hardness measured on the Rockwell B Scale• or an abbreviation for Boron• Bake (Bake-Out) Heat Treat process used in plating to prevent Hydrogen Embrittlement• Bevel Style of washer (square with a taper) used with I beams• Belleville Style of lock washer, also called conical spring washer• BHCS Button Head Cap Screw• BHN Hardness measured with a Brinell Hardness Tester• BS British Standard• C When followed by a number (ex C-35) hardness measured on the

Rockwell C Scale• or an abbreviation for Carbon• CH Case hardened (type of heat treatment)• C/R Cross Recess Drive (typically Phillips style) or Chamfer/Radius• Cad Cadmium Plating• CAD Computer Aided Design/Drafting• Cad/Wax Cadmium Plating with a topcoat of Wax• COO Country of Origin• CRES Corrosion resistant steel (usually refer to 18-8 or 316 stainless steel)• CS (cs) Carbon Steel or Countersunk• DAC (Dac 320) Dacromet Coating (Registered Trademark of Coatings International)• D/C Nut Double Chamfered Nut (distinguish from washer faced)• D/E Double Ended Stud• DIN German Standards Organization• Deltaseal Magnigard coating (registered trademark of Magni Engineered Coatings)• Dorrltech Magnigard coating (registered trademark of Magni Engineered Coatings)• Driseal Pipe Thread (registered trademark of Parker Hannifin)• ET External Thread• FB Flange Bolt• F436 Hardened flat washer with dimensions per ASTM F436• FHCS Flat Head Cap Screw• FIM Full Indicator Measurement• Flng Hex Flange Bolt or Nut• FW Flat Washer• galv Galvanized, typically refers to Hot Dip Galvanized• Gr Grade, refers to strength level of screw or nut (ex: Grade 2, Grade 5 or

Grade 8)• Hardened A product that has been heat treated• HB Hex bolt or Hardness reading measured on the Brinell Scale• H.T Heat Treated

• HCS Hex Cap Screw or High Carbon Steel• H.D.G. Hot Dip Galvanized• Hex Bolt Can refer to either a “bolt” or a “cap screw”• HHCS Hex Head Cap Screw (also an abbreviation for Heavy Hex Cap

Screw)• HRB Hardness measured on the Rockwell B scale• HRC Hardness measured on the Rockwell C scale• HWH Hex Washer Head• ID Identification (usually refers to manufacturer logo)• IFI Industrial Fastener Institute• IH Indented Head• in. Inch• ISO International Standards Organization• ISIR Initial Sample Inspection Report• IT Internal Thread• J429 SAE standard that specifies strength levels of screws• J995 SAE standard that specifies strength levels of nuts• k Short hand for the number 1,000• Keps Nut with a permanently attached washer• Kips 1,000 pounds• ksi Thousand of pounds per square inch• lb (lbs) Pounds• Lb Body Length on screws• LCS Low Carbon Steel• Lg Grip Length (distance from head to full threads) on screws• LH Left Hand Thread• L/W Lock Washer• M Metric or short hand for the number 1,000• Magnigard Magni Coating (Registered Trademark of Magni Engineered Coatings)• Mfg Manufacturer• mm Millimeter• MS Machine screw• MTR Material Test Report• #3 (or #7) Refers to head design of a plow bolt• NC Unified National Coarse Thread• NE (NU, NTE, NTU) Designations that define the thickness of Nylon Insert Lock Nuts• NF Unified National Fine Thread• Nom Nominal (reference dimension)• NPT National Tapered Pipe Thread• p Thread Pitch• P/B Plow Bolt• Ph Dr Phillips Drive (cross recess)• Pl Plain finish• P/N Part Number• Phos (P & O) Phosphate and Oil Coating (typically Zinc Phosphate and Oil)• Pozi Drive Special cross recess (registered trademark of Camcar Textron)• PPAP Production Part Approval Process• psi Pounds per square inch• PZ Pozi-Drive style of cross recess• R Radius• Rb (RB or HRB) Hardness measured on the Rockwell “B” scale• Rc (RC or HRC) Hardness measured on the Rockwell “C” scale• RT Rolled Threads• SAE Society of Automotive Engineers,• when used with washers it means “small OD”• when used with screw or nuts means fine thread

• Screw Can refer to any type of externally threaded fastener but typically a sheet metal screw

• Sems Screw with a permanently attached washer• Serrated Locking serrations on bearing face of screw or nut• SHCS Socket Head Cap Screw• Sl Slotted Drive• SMS Sheet Metal Screw• Sq Square, can refer to square head bolt or square nut• SS or S/S Stainless Steel• St Steel• Taptite Special triangular thread forming screw (registered trademark of

Reminc)• T.H. Through Hardened (type of heat treatment)• TIR Total Indicator Reading• T/S Tapping Screw• Torx 6 Lobe Drive (Torx Drive, registered trademark of Camcar

Textron)• TPI Threads per Inch• TT (TR) Taptite thread (registered trademark of Reminc), also called Tri-Roundular • TTH Threaded to Head• Type 1 (23, 25) Special thread forming or cutting tapping screws• Type AB (F, T) Special thread forming or cutting tapping screws• UNC Unified National Coarse Thread• UNRC Unified National Coarse Thread with Radius Root (standard rolled thread form)• UNF Unified National Fine Thread• UNRF Unified National Fine Thread with Radius Root (standard rolled thread form)• UNJ Unified National Thread with Large Radius Root (special fatigue resistant thread)• UNR Unified National Thread with radius root• USS United States Standard• when used with washers it is for large OD• when used with screws or nuts it means coarse thread• UTS Ultimate Tensile Strength• WAC Width Across Corners• WAF Width Across Flats• W/F Washer Faced (can refer to a Nut or Cap Screw)• Whitworth British Thread Standard (not the same as UN threads)• Y Yellow Chromate• YS Yield Strength• Zn Zinc, usually referencing zinc plating (assumed to be zinc with

clear chromate)• Zn/C (ZC) Zinc Plating with Clear Chromate topcoat• Zn Phos Zinc Phosphate and Oil (same as Phos and Oil)• Zn/Wax Zinc Plating with a topcoat of wax• Zn/Y (ZY) Zinc Plating with Yellow Chromate topcoat