Aero Fasteners

© 2009 Wipro Ltd - Confidential

FASTENERS

IN AEROSPACE

© 2009 Wipro Ltd - Confidential2 © 2009 Wipro Ltd - Confidential2

3

4 QUICK CHANGE FASTENERS, TURN BUCKLES

1 RIVETS

2 BOLTS, SCREWS, NUTS & ANCHOR NUTS

HI LOKS, QUARTER TURN CAM LOCKS

5 GROMETS / WASHERS / SPLIT PINS

© 2009 Wipro Ltd - Confidential3

RIVETS


A Fastener is a hardware device that mechanically joins or affixes two or more objects together.

A rivet is a permanent mechanical fastener. Before it is installed it consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or pre-drilled hole. Then the tail is "upset" (i.e. deformed) so that it expands to about 1.5 times the original shaft diameter and holds the rivet in place. To distinguish between the two ends of the rivet, the original head is called the factory head and the deformed end is called the shop head or buck-tail.

RIVETS


The rivet is placed in a pre-drilled hole and is set by pulling the mandrel head into the rivet body, expanding the rivet body and causing it to flare against the reverse side

Flush rivet

A flush rivet is used primarily on external metal surfaces where good appearance and the elimination of unnecessary aerodynamic drag are important. A flush rivet takes advantage of a countersink hole, they are also commonly referred to as countersunk rivets. Countersunk or flush rivets are used extensively on the exterior of aircraft for aerodynamic reasons. Additional post-installation machining may be performed to perfect the airflow.

RIVETS


1. RIVET LENGTHThe formula for determining rivet length is as follows(1 + 1 / 2) x D + G =L Where : D = the rivet diameter,

G = the grip (total thickness of material), and L = the total length of the rivet.

2. RIVET SPACING & EDGE DISTANCERivet spacing, also referred as rivet pitch, is the distance between the rivets in the same row, and is measured from the rivet center to the rivet center. Transverse pitch is the distance between the rows of rivets, and is measured from the rivet center to rivet center. Edge distance is the distance from the center of the rivet to the edge of the material being riveted. There are no specific rules that apply to every case or type of riveting. There are, however, certain general rules that should be followed. a) RIVET SPACINGRivet spacing (pitch) depends upon several factors, principally the thickness of the sheet, the diameter of the rivets, and the manner in which the sheet will be stressed. Rivet spacing should never be less than three times the rivet diameter. Spacing is seldom less than four times the diameter nor more than eight times the diameter.

RIVETS


b) TRANSVERSE PITCHWhen two or more rows of rivets are used in a repair job, the rivets should be staggered to obtain maximum strength. The distance between the rows of rivets is called “transverse pitch.” Transverse pitch is normally 75 percent of existing rivet pitch, but should never be less than 2 1/2 times the diameter.

c) EDGE DISTANCEThe edge distance for all rivets, except those with a flush head, should not be less than twice the diameter of the rivet shank nor more than four times the diameter of the rivet shank. Flush-head rivets require an edge distance of at least 2 1/2 times the diameter. If rivets are placed to close to the edge of the sheet, the sheet is apt to crack or pull away from the rivets. If they are placed too far away from the edge, the sheet is apt to turn up at the edge.

NOTE : On most repairs, the general practice is to use the same rivet spacing and edge distance that the manufacturer used in the surrounding area, or the structural repair manual for the particular aircraft may be consulted.Figure in below slides shows edge distance, rivet spacing ,Rivet spacing and edge distance.

RIVETS


RIVETS


RIVETS


BOLTS, NUTS & SCREWS


STRUCTURAL SCREWSStructural screws are used for assembling structural parts. They are made of alloy steel and are heat treated. Structural screws have a definite grip length and the same shear and tensile strengths as the equivalent size bolt.

BOLTS NUTS & SCREWS


NUTSAircraft nuts differ in design and material, just as bolts do, because they are designed to do a specific job with the bolt. For instance, some of the nuts are made of cadmium-plated carbon steel, stainless steel, brass, or aluminum alloy. The type of metal used is not identified by markings on the nuts themselves. Instead, the material must be recognized from the luster of the metal. Nuts also differ greatly in size and shape. In spite of these many and varied differences, they all fall under one of two general groups self-locking and nonself-locking. Nuts are further divided into types such as plain nuts, castle nuts, check nuts, plate nuts, channel nuts, barrel nuts, internal-wrenching nuts, external- wrenching nuts, shear nuts, sheet spring nuts, wing nuts, and Klincher locknuts.NONSELF-LOCKING NUTSNonself-locking nuts require the use of a separate locking device for security of installation.There are several types of these locking devices mentioned in the following paragraphs in connection with the nuts on which they are used. Since no single locking device can be used with all types of nonself-locking nuts, you must select one suitable for the type of nut being used.

BOLTS NUTS & SCREWS


BOLTS NUTS & SCREWS


BOLTS & SCREWS


SELF-LOCKING NUTS

Self-locking nuts provide tight connections that will not loosen under vibrations. Self-locking nuts approved for use on aircraft meet critical strength, corrosion-resistance.

The Camloc high-stress panel fastener, is a high-strength, quick-release rotary fastener, and may be used on flat or curved inside or outside accessible panels. The fastener may have either a flush or protruding stud. The studs are held in the panel with flat or cone-shaped washers—the latter being used with flush fasteners in dimpled holes. This fastener may be distinguished from screws by the deep No. 2 Phillips recess in the stud head and by the bushing in which the stud is installed. Ex : For lighting mechanism.

BOLTS NUTS & SCREWS

CAMLOCK MECHANISM


HI LOKS & CAM LOCKS


The last commonly used high strength structural steel rivet

Hi-Lok FastenersThe hi-lok fastener, shown in figure 2-7, combines the features of a rivet and a bolt and is used for high-strength, interference-free fit of primary structures.The hi-lok fastener consists of a threaded pin and threaded locking collar.

HI LOKS


A cam-lock fitting comprising a body having a flow path there through, the flow path having a first opening and a second opening, wherein

a) the second opening is provided by a boss having a proximal end.b) the external surface of the proximal end has a pair of opposed grooves for

accepting the cams of a cam-lock fitting.c) the transverse cross-section of the external surface of the distal end of the

boss is substantially circular.

CAM LOCS


QUICK CHANGE FASTENERS, TURN BUCKLES


QUICK RELEASE PINSThese pins of stainless steel, are made to exacting standards. Pushing the button on top, it contracts and releases two (or four) balls at the end of the shank. These balls lock onto and release from the part for fast removal.

Pins with recessed release button to prevent accidental release

Extruded aluminum T-Handles are designed to withstand high tensile loads, assuring excellent impact & crack resistance. Includes attaching ring. Made from corrosion resistant 17-4 PH stainless steel. Double shear Min: 9200. Tensile strength Min:230 .


TURN BUCKLES

Turnbuckles are used in rigging to join wire-rope or cable to an anchor point or other length of wire. They have a screw thread for precise length and tension adjustment. Most turnbuckles are forged or cast from stainless steel or low carbon steel. They are machined to product specifications and then quenched, tempered, plated with zinc, or hot-galvanized.

Turnbuckles are made of aluminum, brass & bronze, stainless steel & steel.


GROMETS / WASHERS / SPLIT PINS


GROMMETIf metal or another hard material has a hole made in it, the hole may have sharp edges. Electrical wires, cord, rope, lacings, or other soft vulnerable material passing through the hole can become abraded or cut, or electrical insulation may break due to repeated flexing at the exit point. Rubber, plastic or plastic coated metal grommets are each used to avoid this. The smooth and sometimes soft inner surface of the grommet shields the wire from damage.

Most common usage is to strengthen the holesfor boot lacing.

GROMMET


WASHERSWashers such as ball socket and seat washers, taper pin washers, and washers for internal-wrenching nuts and bolts have been designed for special applications.

SPLIT PINSCotter pins are used to secure bolts, screws, nuts, and pins. Some cotter pins are made of low-carbon steel, while others consist of stainless steel and are more resistant to corrosion. Also, stainless steel cotter pins may be used in locations where nonmagnetic material is required. Regardless of shape or material, all cotter pins are used for the same general purpose safetying.

Split washerWave washer

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