Aircraft Hardware

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					Identification and AN Specification
Overview
 In the end, you should be able to:
    Distinguish aircraft hardware from common hardware,
    Know the AN numbering convention,
    Be able to match a fastener to its AN number,
    Select the proper hardware from a blue print drawing,
    Be able to order hardware from a supplier,
    Know where to find AN information.
Aircraft Hardware
 “Hardware” is the term used describe the various types
  of fasteners and small items used to assemble aircraft
  structures.
 Only hardware with traceability to an approved
  manufacturing process or source should be used.
 Threaded fasteners and rivets are the most commonly
  used fasteners.
AN Hardware Includes
 Bolts          Fittings
 Nuts           Clamps
 Washers        Bushings
 Screws         Angle Brackets
 Cotter Pins    Sheet Metal Screws
 Rivets         Cowling fasteners
                 Much more
Bolts
Nuts
Washers
Screws
Cotter Pins
Rivets
Specification Conventions
 AN – Air Force / Navy
 NAS – National Aerospace Standards
 MS – Military Standards
 AMS – Aeronautical Material Specifications
 SAE – Society of Automotive Engineers
 MIL – Military Specifications
This Lesson
 AN Specifications
    Was the primary standard in 1946.
    Still widely used today for most hardware.
 Bolts, Washers, Nuts, Cotter Pins
 Occasional references to NAS and MS specifications.
   NAS and MS has more fasteners than AN.
   Conversion tables available for cross references.
AN Specifications - Overview
 AN3 - AN20 – Standard Bolts
 AN21 - AN36 – Clevis Bolts
 AN42 – AN49 – Eye Bolts
 AN73 – AN81 – Drilled Head Bolts
 AN310 – Castle Nut
 AN315 and AN335 – Plain Nut
 AN960 and AN970 – Washers
 AN935 and AN936 – Lock Washers
 AN380 – Cotter Pins (Standard)
Bolts
 Most bolts used on aircraft are
   General-purpose
   Internal-wrenching
   Close-tolerance


 On the Aeronca Champ, most are General Purpose.
Bolt Materials
 Standard Aircraft Bolts
    High-strength type 4037 or 8740 alloy steel.
    Cadmium plated for corrosion resistance.
    Minimum tensile strength 125,000 PSI.
    Only specific bolt head markings allowed.
Bolt Materials
 Common Home Depot bolts (non-aviation)
    Made of a low carbon (mild) steel.
    No corrosion resistance.
    Low tensile strength; about 55,000 PSI.
    Identified by lack of proper AN markings.
    Often have coarse threads.
Aircraft Bolt Identification
 Bolts are identified by markings on the bolt heads.
    Denote the materials of which the bolt is made.
    Standard vs. special-purpose bolts.
    Sometimes includes the manufacture.

              *
    Usually a ‘ ’ or an ‘X’


 Challenges
    Keep your bolts separated to avoid confusion.
    Know your sources.
    Not always easy to remember the various markings.
    Need a chart to know the various markings.
43.13-2B
Bolt Terminology
 Length – Total distance from under head to the tip.
 Grip – The unthreaded part.
 Diameter– Thickness of the bolt.
 Thread size – Pitch of the thread.
Other Bolt Terminology
 Thread Length
 Head Thickness
 Head Width
 These are fixed sized for most aircraft bolts.
AN Bolt Numbering Template
AN Bolt – Series Number
 Standard AN bolts are numbered by the diameter.
 Numbered in sixteenths of an inch.
   AN3 – 3/16” diameter (3/16)
   AN4 – 1/4“ diameter (4/16)
   AN5 – 5/16” diameter (5/16)
   AN6 – 3/8” diameter (6/16)
   AN7 – 7/16” diameter (7/16)
   ……
   AN20 – 1-1/4” diameter (16/16 + 4/16)
AN Bolts – Diameter vs Thread size
 Each AN bolt diameter has only one:
    Thread pitch.
    Thread length.

     AN Diameter   Threads per Inch   Thread Length
     AN3           32                 3/8”
     AN4           28                 7/16”
     AN5           24                 9/16”
     AN6           24                 9/16”
     AN7           20                 9/16”
     AN8           20                 9/16”
AN Bolt – Dash Number
 Dash numbers represent the length of the bolt.
 Numbered in eighths of an inch.
   -4 - 1/2” length (4/8)
   -5 - 5/8” length (5/8)
   -6 - 3/4” length (6/8)
   -7 - 7/8” length (7/8)
   -10 - 1” length (1 + 0/8)
   -11 - 1 1/8” length (1 + 1/8)
   -12 - 1 1/4” length (1 + 2/8)
   …..
   -24 - 2 1/2” length (2 + 4/8)
AN Bolt – Selecting the Length



 The grip length should equal the thickness of the
  materials being bolted together.
 A nut is not to run to the bottom of the bolt threads.
 If grip is too long, you can use washers.
   Do not use more than 1/8” of washers (typically two
    standard AN washers.)
   Use next length bolt if needed, which is 1/8” shorter.
AN Bolt – Quiz
 AN3-7
 AN6-20
 AN4-17
 AN5-18
AN Bolts – Safety with Cotter Pin
 Available with or without shank drilled for cotter pin
 or undrilled for stop nut application.
AN Bolts – Safety with Cotter Pin
 Add the letter “A” to the dash number for undrilled
  shank.
 No letter for drilled shank.




              AN5-10
                                        AN5-10A
AN Bolts – Safety with Wire
 Available with or without drilled head for safety wire.
AN Bolts – Safety with Wire
 Add the letter “H” to the AN number for drilled head.
 No letter for undrilled head. (Normal)
 Not to be confused with AN73 to AN81, which have a
 deeper head.




     AN4H-15                 AN4-12A            AN76-6
AN Bolts – Measuring
 A standard rule can be used to measure existing bolts.
AN Bolts –
Measuring
 Bolt Gauges are an easy
 and accurate way to
 measure an existing bolt.
AN Bolts - Measuring
Ordering AN Bolts
AN Nuts – Plain Hex Nuts
 AN315 – Standard




 AN316 – Checknut
AN Nuts – Plain Hex Nuts
 Rugged construction and can carry the same high
  tension load as the popular castle nut.
 It requires an auxiliary locking device such as a check
  nut or lock washer.
 AN316 hex check nuts can carry half the tension load
  of the AN315 nut.
 They are used as a locking device for plain nuts, set
  screws, rod ends, etc.
 Appears to be the only AN nuts available in both
  right-hand and left-hand thread.
 Add R or L after dash number for right-hand or left-
  hand thread.
AN Nuts – Plain Hex Nuts



                                  -- Thread Direction
                           AN315-4R
                                  -- Dash Number
AN Nuts – Plain Hex Nuts
AN Nuts – Castle Nuts
 AN310 – Thick nut used for tinsile loads




 AN320 – Thin nut used only for shear loads
AN Nuts – Castle Nuts
 Fabricated from steel & cadmium plated.
 The slots in the nut accommodate a cotter pin for
  safety purposes.
 AN310 castle nuts are used with drilled-shank bolts,
  clevis bolts, eye bolts and studs.
 The thinner AN320 castellated shear nut has half
  tensile rating of the AN310 nut.
 AN320 is used with clevis bolts & threaded taper pins
  which are subject to shearing stress only.
AN Nuts – Castle Nuts

 AN310-5
          -- Dash Number
AN Nuts – Castle Nuts
AN Cotter Pins
 AN380 - Cadmium plated low-carbon steel




 AN381 - Corrosion resisting steel




 Now MS24665
AN Cotter Pins


                 AN380-2-8
                        -- Length ( 1/4” )
                        -- Diameter (1/32” )
AN Cotter Pins
AN Nuts – Elastic Stop Nuts
 AN365 – Standard




 AN364 – Thin for shear loads only.
AN Nuts – Elastic Stop Nuts
 Has a fiber or nylon insert locked into the end of the
  nut, with a hole slightly smaller than the diameter of
  the bolt.
 Screws down freely until the nylon is reached, then a
  wrench is required.
 Should not be used in applications where the nut and
  bolt are subject to rotation.
 To ensure that the nylon-insert grips all the bolt
  threads, the complete chamfer on the end of the bolt
  must stick out beyond the nylon-insert.
 Should not be used where temperatures exceed 250
  degrees.
AN Nuts – Elastic Stop Nuts

 AN365-440
          -- Dash Number (Bolt size)
AN Nuts – Elastic Stop Nuts
AN Washers
 AN960 standard washers



 AN970 large washers




 Standard washers are 1/16”. Some available at 1/32”.
AN Washers
 AN960
    Provides smooth bearing surface for nut,
    Serves as shims to obtain the correct grip length for a
     bolt and nut assembly,
    Prevents sharp edges under lock washers from damaging
     material clamped.

 AN970
    Much larger outside diameter,
    Used when bolting wood surfaces together,
    Spreads force applied by bolt and nut over larger area of
     the wood to prevent crushing.
AN Washers
 AN960-416
AN Washers
 AN970-4
Practice
 Except as a last resort, do not torque a bolt by turning it.
 Elastic stop nuts may be reused many times, certainly
  until the fiber has lost its locking friction or has become
  brittle with age. If you can turn the nut up all the way
  with your fingers, replace it.
Practice
 Since bolt lengths are made in 1/8" increments,
 washers may sometimes be necessary to obtain the
 correct grip length for a bolt that is a little too long. A
 maximum of two standard 1/16" thick washers are
 sufficient to correct for a slightly long bolt. If not, use
 the next size shorter bolt.
Practice
 No self-respecting homebuilder will ever allow himself
 to be caught using a pair of pliers or adjustable wrench
 to tighten an aircraft nut.
AN Hardware



   Questions?
Thank You.

				
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