AVIATIONEU NEW ERA ASTM A193 Grade B6 Series stainless steel stud bolts are manufactured from the ferritic grade AISI 410 stainless steel and can be heat-treated and machined to minimum of 110-ksi or 760 Mpa tensile strength. Like other fasteners in this seies, apart from their high tensile strength, they exhibit excellent resistance to corrosion, durability as well as a long functional work life. They can be used in different applications in industries that demand high tensile strength and corrosion resistance. Sourced by certified manufacturers they are competively priced and offered in different diameters and lengths. Sold by the piece (pc.) in increments of 10 pieces with Minimum Order Quantity (MOQ) 100 pieces. Appearing price is for reference only and differentiates based on wanted bolt sizes. Please contact us for a quotation.

AVIATIONEU NEW ERA ASTM A324 Grade 10.9 Series high tensile hexagonal head threaded bolts are produced from medium carbon steel, medium carbon steel alloy and low carbon boron steel with heat treatment by both quenching and tempering.  They meet ASTM A324 Grade BD and SAE J429 standards. These bolds feature high tensile strength and good wear resistance and are used in automotive applications and for bolting large and forged parts. 

Nominal Tensile Strength: 1.000 Megapascal (MPa) or 1.000 N/sqr. mm , Yield Stress: 900 Megapascal (MPa) or 900 N/sqr. mm 

They are offered in different finishes (zinc plated, plain or hot dip galvanised) and different standard, coarse and fine thread sizes (diameter M20 to M100 mm / 3/4" to 3.1/2").  Sold by the piece (pc.) in increments of 10 pieces with Minimum Order Quantity (MOQ) 100 pieces. Appearing price is for reference only and differentiates based on wanted bolt sizes. Please contact us for a quotation.

AN 22 Series Clevis bolts are available in NEW SURPLUS condition. Availability till stock exhaustion. They are special-purpose bolts with a a slotted brazier type head and used where a large shearing stress occurs (never in tension). Available with drilled or undrilled shank (designated by the letter "A" after the dash number for undrilled shank). 

Machine screws are one of the more widely used products among dozens of standard fastener types. They can be either coarse-threaded or fine-threaded, and are usually available with a wide range of head types. Usually stronger than many other screw types, they are used for fastening metal parts and panels securely together in a range of construction and other applications including aerospace, machinery, vehicles, engines, tool assemblies, electronic devices, and large-scale industrial equipment. 

Sourced from quality producers,  machine screws are offered as part of our own branded (AVIATIONEU NEW ERA) product lines conforming to aerospace/military or industrial standards/specifications.  They come in different sizes, head types, materials and thread gradings. 

AVIATIONEU NEW ERA NAS860/NAS870 series of machine (non structural) screws (also termed as bolts) are aeronautical standard high strength, close tolerance, short thread, Philips head recess screws.   Both series are made from 8616 alloy steel, heat treated to 160-180 KSI and Cadmium plated per QQ-P-416 Type II. Also offered from 8716 A286 corrosion resistant steel (CRES), heat treated to 160-180 KSI.They are offered in different thread sizes and grip lengths in inches with undrilled or drilled shanks and sold in pieces. Screw size number is after the basic part number (e.g. NAS8602 for size 2 screws). Grip Length in 1/16ths inches after the dash. The following letters are also used:

"D" after the dash number indicates a drilled shank

"A" after the basic part number prefix and the letter "D", if applicable, indicates an aluminum coating

"U" after the basic part number prefix and the letter "D", if applicable, indicates unplated and passivated

 For more information, please refer to the attached reference table or contact us. 

The NAS1630 Series screws are pan head, short thread, offset cruciform machine screws offered as part of our own branded (AVIATIONEU NEW ERA) product lines. These screws use PHILLIPS Screw-Torq-Set® drive system with significant benefits outlined below. Sourced from quality manufacturers they are offered in alloy steel or corrosion resistant steel (CRES) and different thread sizes and legths in inches. Sold in packs each containing a specified number of screws. The number of screws in each pack is specified after the letters "PK" in the product reference code (SKU).

PHILLIPS Screw-Torq-Set® Drive System Features & Benefits

Offset cruciform shape with straight wing walls for greater torque transfer.

Removal walls larger than drive walls. Facilitates disassembly without drill outs.

Specific driver for each diameter fastener. Assures optimum torque for each size and strong head configuration.

Compatible with standard PHILLIPS ACR® ribbed TORQ-SET® drivers. Allows use of ribbed tools with standard screws

PSC quality inspections. Assures global system quality and compatibility.

Screws, bolts and nuts are standard fastening hardware widely used in a range of applications. 

Internal wrenching (also known as Allen) fasteners are threaded fasteners. Screws and bolts have a drive recess within the head allowing the insertion of an internal wrench for their installation or removal. Allen socket set screws are blind (headless) fasteners with an internal hex drive offered in different styles (regular cap screw and flat and button type) while Allen nuts are cylindrical nuts internally threaded on one side with an Allen socket on the other. These fasteners are produced by different manufacturers and come in different styles, inch or Metric sizes, materials, finishes,  and coarse or fine threadings. They are offered as OEM parts or parts of AVIATIONEU NEW ERA product lines. Sold in pieces or packs of specified number of pieces per pack as designated by the number after the letters "PK" in the product reference code (SKU). 

Internal wrenching fasteners for aerospace applications are designed and intended for use in aircraft construction and repair and conform to Military or Aerospace Standards. Aerospace Industries Association Standard NASM 20004 through 20024 internal wrenching bolts supersede respective part numbers of MS 20004 through 20024 which in turn have superseeded those of older National Aerospace Standard NAS NAS 144 to 158 series. Fabricated from 160-180 ksi high-strength steel they are intended for use in both tension and shear applications. 

Socket screws for aerospace and military uses come in different sizes and meet aerospace/military standards including AN565 (superseded by NASM565), NAS1081, MS18063, MS18064, MS51021, MS51023, MS51029, MS51031, MS51038, MS51045, MS51963, MS51964, MS51965, MS51966. Those of AN565 (NASM565) standard are headless hex and fluted socket set screws while their MS51963 standard counterparts are cup point hex socket set screws.  Both are made of high-quality steel and they are designed to deliver maximum holding pressure Typically used to bind parts onto shafts. Available in cup or cone point styles, in different thread sizes and lengths in inches.

81791 internal wrenching  nuts are self-locking, high-strength, corrosion and oxidation resistant nuts made of nickel-chromium alloy with cadmium plating. These nuts are catalogued and supplied in different sizes as part numbers of TEXTRON AVIATION (separately listed).

For more information, please refer to the Product Description section, the supplied documentation or contact us.

AN Clevis bolts are manufactured from nickel steel alloy, SAE 2330 and cadmium plated in same manner as AN3 - AN8 aircraft bolts.They are special-purpose bolts with a a slotted brazier type head and used where a large shearing stress occurs (never in tension). Minimum tensile strength 125,000 PSI. They are available with drilled or undrilled shank (designated by the letter "A" after the dash number for undrilled shank). For the AN12-AN23 bolts the second digit denotes the fine thread machine screw size (e.g. for AN21 the size is 6-40, for AN22 8-36 and for AN23 10-32). For the AN24-AN36 bolts the second digit denotes the diameter in 1/16 inch increments (AN25 has a diameter of 5/16 inch).

Close tolerance bolts, designed with a greater emphasis on measurement accuracy than other types of bolts, are commonly used in the aerospace manufacturing industry. They are threaded fasteners with a shank and head and a tolerance of just +0.000, -0.0005 inch as an acceptable range of variance. The shank is threaded, thus allowing them to be driven into a threaded hole. They intend to eliminate problems appearing when using traditional bolts which have a greater acceptable range of variance. Close tolerance bolts have closer shank tolerances than that of traditional bolts and fit more securely in threaded holes. For some fastening applications, traditional bolts may suffice. For sensitive fastening applications in which precision is required, close tolerance bolts are typically used. When selecting close tolerance instead of traditional bolts the drive type should be considered. Most close tolerance bolts have a recess within their head that supports a specific bit, such as a Phillips head bit. Regarding their threading, all close tolerance bolts, as well as traditional bolts, have threading. But the way in which the threading is designed may vary. Some bolts have more threading on their shank than others, and some bolts have finer threading than others.

Close tolerance bolts are offered in different materials with high-carbon steel being a common material used in their construction. 

Army & Navy (AN) close tolerance bolts are offered as part of our own labelled (AVIATIONEU NEW ERA) lines of fasteners. They are sourced from quality manufacturers and structured in different series (AN 173/174/175/176/178/180).

The following letters after the basic part numbers specify the material, finish and drilling condition of these bolts.

First Number after AN Basic designates the Diameter. 

"-" for Steel, Cad II plated, no head hole

"C" in place of (-) for Corrosion Resistant Steel (CRES)

"H" in place of (-) or after (C) for bolts with a head hole

"A" In the end of the PN  for bolts with no shank hole

National Aerospace Standard (NAS) machine bolts are commonly used in aircraft, space shuttles, military vehicles, drones, and other high-performance applications. They are offered in different series to meet application requirements.

Those of NAS 6203 through NAS 6220 series, superseding their NAS 11(xx) counterparts, are tension hexagon head high strength close tolerance short-thread alloy steel bolts with a minimum tensile strength of 160,000 psi and a minimum shear strength of 95,000 psi. 

They are made from different steel alloys such as 4140 (UNS G41400) or  4340 (UNS G43406) with either Cadmium Plate  Type II, Class 2 or Chromium Plate on shank only with all other surfaces cadmium plated.

Depending on the series they come in different nominal diameters in inches (e.g. NAS 6203 0.1875" (3/16"), NAS 6204 0.25" (1/4"), NAS 6205  0.3125" (5/16"), NAS 6206 0.375" (3/8"), NAS 6208 0.500" 1/2") or NAS 6210 0.625" (5/8") grips (in 1/16” increments beginning at 1/16”), thread and overall fastener lengths. They can be supplied undrilled or with drilled head and/or thread and with or without locking elements (nylon or equivalent). Sourced from quality manufacturers, these bolts are listed according to their series, and offered either as OEM parts or as parts of our own labelled (AVIATIONEU NEW ERA) product lines (see the respective listings). Sold in pieces or packs of specified number of bolts per pack designated by the number after the letters "PK" in the product reference code (SKU).

The following letters after the basic part numbers specify the material, finish, drilling condition, and self-locking capability of these bolts.

No Finish Code for Cadmium II plated bolts

"C" for Chromium plated bolts (shank only)

"L" for Self-locking bolts

"P" for Self-locking bolts with patch type locking element only

Grip Dash Number indicating grip in .0625 increments

"D" after the grip dash number for drilled thread bolts

"H" after the grip dash number for bolts with drilled head

More than one code letters may be used in sequence.

PN Examples:

NAS6204-10 - NAS 6204 Series Bolt, .2500-28 Thread, .625 Grip, Undrilled, Non-locking, Alloy Steel Cadmium II Plated.

NAS6204-10D - Same bolt as above with Drilled Thread.

For more information, please refer to the supplied documentation or contact us.

Machine screws are one of the more widely used products among dozens of standard fastener types. They can be either coarse-threaded or fine-threaded, and are usually available with a wide range of head types. Usually stronger than many other screw types, they are used for fastening metal parts and panels securely together in a range of construction and other applications including aerospace, machinery, vehicles, engines, tool assemblies, electronic devices, and large-scale industrial equipment. 

Sourced from quality producers,  machine screws are offered as part of our own branded (AVIATIONEU NEW ERA) product lines conforming to aerospace/military or industrial standards/specifications.  They come in different sizes, head types, materials and thread gradings. NAS Standard Machine Screws meet aerospace standards and come in different types and sizes structured in different series including NAS1101, NAS1102, NAS1189, NAS1190, NAS1191, NAS1635, NAS1801, NAS1802, NAS220, NAS229, NAS333, NAS514, NAS517, NAS560, NAS583, NAS600, NAS623 and NAS662.

AVIATIONEU NEW ERA NAS333/NAS334 series of machine (non structural) screws (also termed as bolts) are aeronautical standard 100 Deg. standard flush head, shear close tolerance screws. They are made from alloy steel per MIL-S-6049 with a Cadmium finish per QQ-P-416 Type II. They are both offered in different thread sizes, grips and lengths in inches and sold in pieces. CPA indicates a plated Phillips recess. The length and grip of the screw are indicated by numbers after the last dash in the product part number. For more information, please refer to the supplied documentation or contact us. 

The NAS1581 Series screws  (also termed as bolts) are high strength, close tolerance, reduced (shear) head, countersunk screws offered as part of our own branded (AVIATIONEU NEW ERA) product lines. They come in different materials and finishes designated by the following letters in their product reference number (SKU) which is formed as a combination of the material, diameter, drive style, grip length and option of the screw:

Materials

(A) or (F) = Alloy Steel, 4140,4340 or 8740, Heat treated to 160-180ksi. Cad 2 plated. Material Code (A) has been superseded by Code (F)

(C) = Corrosion Resistant (A286) Steel, Heat treated to160-190ksi. Cad 2 (optional)

(V) = Titanium (6al-4v) Heat treated to 160-180ksi. No finish. Material Code (V) has been cancelled Dec.1991

Diameters: Numbers 3 to 10

Drive Styles

(R)= Offset Cruciform, (Torq-set) R, for diameters 3,4 & 5.

(T) = Offset Cruciform, (Torq-set) R for diameters 6 and up.

(H) = Dovetail Slot

Grip Lengths

The grip length  for Countersunk Head Fasteners (T in the supplied table) includes the head and extends to the full cylindrical portion of the shank. The Grip Length for NAS1581 Series screws is measured in 1/16ths of an inch. + or - .010

AVIATIONEU NEW ERA NAS1581 Series screws are offered in pieces or kits for convenience and economy. 

For more information, please refer to the supplied documentation or contact us.

Machine screws are one of the more widely used products among dozens of standard fastener types. They can be either coarse-threaded or fine-threaded, and are usually available with a wide range of head types. Usually stronger than many other screw types, they are used for fastening metal parts and panels securely together in a range of construction and other applications including aerospace, machinery, vehicles, engines, tool assemblies, electronic devices, and large-scale industrial equipment. 

Sourced from quality producers,  machine screws are offered as part of our own branded (AVIATIONEU NEW ERA) product lines conforming to aerospace/military or industrial standards/specifications.  They come in different sizes, head types, materials and thread gradings. NAS Standard Machine Screws meet aerospace standards and come in different types and sizes structured in different series including NAS1101, NAS1102, NAS1189, NAS1190, NAS1191, NAS1635, NAS1801, NAS1802, NAS220, NAS229, NAS333, NAS514, NAS517, NAS560, NAS583, NAS600, NAS623 and NAS662.

AVIATIONEU NEW ERA NAS583 series of machine (non structural) screws are aeronautical 100 deg. alloy steel cadmium plated flush head close tolerance machine screws  offered in different thread sizes and lengths in inches and sold in packs with number of pieces per pack specified after the letters "PK" in the product reference number (SKU). For more information, please refer to the supplied documentation or contact us. 

National Aerospace Standard (NAS) machine bolts are commonly used in aircraft, space shuttles, military vehicles, drones, and other high-performance applications. They are offered in different series to meet application requirements.

Those of NAS 6203 through NAS 6220 series, superseding their NAS 11(xx) counterparts, are tension hexagon head high strength close tolerance short-thread alloy steel bolts with a minimum tensile strength of 160,000 psi and a minimum shear strength of 95,000 psi. 

They are made from different steel alloys such as 4140 (UNS G41400) or  4340 (UNS G43406) with either Cadmium Plate  Type II, Class 2 or Chromium Plate on shank only with all other surfaces cadmium plated.

Depending on the series they come in different nominal diameters in inches (e.g. NAS 6203 0.1875" (3/16"), NAS 6204 0.25" (1/4"), NAS 6205  0.3125" (5/16"), NAS 6206 0.375" (3/8"), NAS 6208 0.500" 1/2") or NAS 6210 0.625" (5/8") grips (in 1/16” increments beginning at 1/16”), thread and overall fastener lengths. They can be supplied undrilled or with drilled head and/or thread and with or without locking elements (nylon or equivalent). Sourced from quality manufacturers, these bolts are listed according to their series, and offered either as OEM parts or as parts of our own labelled (AVIATIONEU NEW ERA) product lines (see the respective listings). Sold in pieces or packs of specified number of bolts per pack designated by the number after the letters "PK" in the product reference code (SKU).

The following letters after the basic part numbers specify the material, finish, drilling condition, and self-locking capability of these bolts.

No Finish Code for Cadmium II plated bolts

"C" for Chromium plated bolts (shank only)

"L" for Self-locking bolts

"P" for Self-locking bolts with patch type locking element only

Grip Dash Number indicating grip in .0625 increments

"D" after the grip dash number for drilled thread bolts

"H" after the grip dash number for bolts with drilled head

More than one code letters may be used in sequence.

PN Examples:

NAS6204-10 - NAS 6204 Series Bolt, .2500-28 Thread, .625 Grip, Undrilled, Non-locking, Alloy Steel Cadmium II Plated.

NAS6204-10D - Same bolt as above with Drilled Thread.

For more information, please refer to the supplied documentation or contact us.

AN hex head bolts in different series are offered under AVIATIONEU NEW ERA product series. Sourced from quality vendors, these bolts are manufactured to the US Army-Navy (AN) standard, predecessor to Mil-Spec (MS), superseded by the National Aerospace Standard (NAS). Commonly used in aviation for either tensile/shear load applications. Made from high-strength type 4037 or 8740 alloy steel or 431 Stainless Steel (CRES) and cadmium plated for superior corrosion resistance (compared to commercial grade zinc plated bolts) they are offered with shank drilled for cotter pin or undrilled for stop nut application, and with a drilled head for safety wire or without. Minimum Tensile Strength (Steel and CRES) - 125,000psi. The length of AN aircraft bolts is measured from under the head to the end of the shank. The "grip" is the unthreaded portion of the shank. Threads are pressed into the steel, not cut, thus maintaining strength throughout the entire shank. The surface under the head of AN bolts is designed to be a bearing surface to reduce non-uniform stress as the bolt is torqued thus reducing premature fatigue. The following letters are used in the product part  numbers.

"A" after the dash number for bolts with undrilled shank

"C"  for bolts made of 431 Stainless Steel (CRES)

"H" after the AN number for bolts with drilled head (eg. AN8H-15)

 AN3 through AN20 Series bolts are superseded by NASM3 through 20 Series. The part numbers in both series have not been changed. 

Specification Details:

AN3 through AN20 (REV. 12), Military Specification Sheet: Bolt -Machine, Aircraft [superseded by NASM3 through 20]. This specification covers aircraft machine bolts part numbers, AN3, AN4, AN5, AN6, AN7, AN8, AN9, AN10, AN14, AN16, AN17, AN18, and AN20. AN3 THRU AN20  is canceled and superseded by NASM3 THRU NASM20. The Part Identification Number (PIN) for AN3 THRU AN20 REV. 12 and the part number for NASM3 THRU NASM20 are identical. The part numbers have not been changed.

Structural screws are made of alloy steel, are properly heat treated, and can be used as structural bolts. Those commonly used in aircraft applications are manufactured to aerospace/military standards/specifications. They are offered as part of our own branded (AVIATIONEU NEW ERA) product lines structured in different series based on the standard of their conformance. Some of the screws commonly used include NAS204 through NAS235 and AN509/AN525 series. 

AN525/AN525R Series high-strength structural washer head (AN525) and cross-recessed (Phillips) head (AN525R) screws, fabricated from alloy steel per specification QQ-S-689. Tensile strength 125,000 PSI. Cadmium plated per QQ-P-416A, Type II, Class 3.  

The AN525 washer head structural screws provide a large contact area. The AN509R (100° countersunk) Phillips head screws are used in countersunk holes where a flush surface is necessary. These have been replaced by MS24694 Series structural screws of the respective materials and finishes.

Structural screws have a definite grip and the same shear strength as a bolt of the same size. Shank tolerances are similar to AN hex head bolts, and the threads are National Fine. Structural screws are available with round, brazier, or countersunk heads. The recessed head screws are driven by either a Phillips or a Reed and Prince screwdriver. Sourced from quality suppliers, these structural screws are offered as part of our own labelled (AVIATIONEU NEW ERA) product lines in different thread sizes and lengths in inches and sold in pieces. For more information, please refer to the individual product presentations, the supplied documentation or contact us.

Machine screws are one of the more widely used products among dozens of standard fastener types. They can be either coarse-threaded or fine-threaded, and are usually available with a wide range of head types. Usually stronger than many other screw types, they are used for fastening metal parts and panels securely together in a range of construction and other applications including aerospace, machinery, vehicles, engines, tool assemblies, electronic devices, and large-scale industrial equipment. 

Sourced from quality producers,  machine screws are offered as part of our own branded (AVIATIONEU NEW ERA) product lines conforming to aerospace/military or industrial standards/specifications.  They come in different sizes, head types, materials and thread gradings. NAS Standard Machine Screws meet aerospace standards and come in different types and sizes structured in different series including NAS1101, NAS1102, NAS1189, NAS1190, NAS1191, NAS1635, NAS1801, NAS1802, NAS220, NAS229, NAS333, NAS514, NAS517, NAS560, NAS583, NAS600, NAS623 and NAS662.

AVIATIONEU NEW ERA NAS517 series of machine (non structural) screws are aeronautical 100 deg. high strength cross recessed flush head close tolerance machine screws. They are made from alloy steel with a Cadmium finish per QQ-P-416 Type II and feature a 160 - 180 KSI tensile strength. They are both offered in different thread sizes and lengths in inches and sold in pieces. For more information, please refer to the supplied documentation or contact us. 

AN 21 Series Clevis bolts are available in NEW SURPLUS condition. Availability till stock exhaustion. They are special-purpose bolts with a a slotted brazier type head and used where a large shearing stress occurs (never in tension). Available with drilled or undrilled shank (designated by the letter "A" after the dash number for undrilled shank). 

National Aerospace Standard (NAS) machine bolts are commonly used in aircraft, space shuttles, military vehicles, drones, and other high-performance applications. They are offered in different series to meet application requirements.

Those of NAS 6203 through NAS 6220 series, superseding their NAS 11(xx) counterparts, are tension hexagon head high strength close tolerance short-thread alloy steel bolts with a minimum tensile strength of 160,000 psi and a minimum shear strength of 95,000 psi. 

They are made from different steel alloys such as 4140 (UNS G41400) or  4340 (UNS G43406) with either Cadmium Plate  Type II, Class 2 or Chromium Plate on shank only with all other surfaces cadmium plated.

Depending on the series they come in different nominal diameters in inches (e.g. NAS 6203 0.1875" (3/16"), NAS 6204 0.25" (1/4"), NAS 6205  0.3125" (5/16"), NAS 6206 0.375" (3/8"), NAS 6208 0.500" 1/2") or NAS 6210 0.625" (5/8") grips (in 1/16” increments beginning at 1/16”), thread and overall fastener lengths. They can be supplied undrilled or with drilled head and/or thread and with or without locking elements (nylon or equivalent). Sourced from quality manufacturers, these bolts are listed according to their series, and offered either as OEM parts or as parts of our own labelled (AVIATIONEU NEW ERA) product lines (see the respective listings). Sold in pieces or packs of specified number of bolts per pack designated by the number after the letters "PK" in the product reference code (SKU).

The following letters after the basic part numbers specify the material, finish, drilling condition, and self-locking capability of these bolts.

No Finish Code for Cadmium II plated bolts

"C" for Chromium plated bolts (shank only)

"L" for Self-locking bolts

"P" for Self-locking bolts with patch type locking element only

Grip Dash Number indicating grip in .0625 increments

"D" after the grip dash number for drilled thread bolts

"H" after the grip dash number for bolts with drilled head

More than one code letters may be used in sequence.

PN Examples:

NAS6204-10 - NAS 6204 Series Bolt, .2500-28 Thread, .625 Grip, Undrilled, Non-locking, Alloy Steel Cadmium II Plated.

NAS6204-10D - Same bolt as above with Drilled Thread.

For more information, please refer to the supplied documentation or contact us.

Different bolts used on Textron Aviation Cessna, Beechcraft and Hawker aircraft. Also available as FAA-PMA approved parts from other manufacturers.

AN hex head bolts in different series are offered under AVIATIONEU NEW ERA product series. Sourced from quality vendors, these bolts are manufactured to the US Army-Navy (AN) standard, predecessor to Mil-Spec (MS), superseded by the National Aerospace Standard (NAS). Commonly used in aviation for either tensile/shear load applications. Made from high-strength type 4037 or 8740 alloy steel or 431 Stainless Steel (CRES) and cadmium plated for superior corrosion resistance (compared to commercial grade zinc plated bolts) they are offered with shank drilled for cotter pin or undrilled for stop nut application, and with a drilled head for safety wire or without. Minimum Tensile Strength (Steel and CRES) - 125,000psi. The length of AN aircraft bolts is measured from under the head to the end of the shank. The "grip" is the unthreaded portion of the shank. Threads are pressed into the steel, not cut, thus maintaining strength throughout the entire shank. The surface under the head of AN bolts is designed to be a bearing surface to reduce non-uniform stress as the bolt is torqued thus reducing premature fatigue. The following letters are used in the product part  numbers.

"A" after the dash number for bolts with undrilled shank

"C"  for bolts made of 431 Stainless Steel (CRES)

"H" after the AN number for bolts with drilled head (eg. AN3H-15)

 AN3 through AN20 Series bolts are superseded by NASM3 through 20 Series. The part numbers in both series have not been changed. 

Specification Details:

AN3 through AN20 (REV. 12), Military Specification Sheet: Bolt -Machine, Aircraft [superseded by NASM3 through 20]. This specification covers aircraft machine bolts part numbers, AN3, AN4, AN5, AN6, AN7, AN8, AN9, AN10, AN14, AN16, AN17, AN18, and AN20. AN3 THRU AN20  is canceled and superseded by NASM3 THRU NASM20. The Part Identification Number (PIN) for AN3 THRU AN20 REV. 12 and the part number for NASM3 THRU NASM20 are identical. The part numbers have not been changed.