STRENGTH THROUGH THIS SECTION IS 75% OF SHEET WITHOUT HOLES.
D = DIAMETER OF 40 RIVET (PREFER- ABLY ABOUT 3x
THICKNESS OF
THICKER SHEET) 2D →4Dx - 20 (A) DOUBLE ROW
CAN DO TA SA NOTES WITHOUT HOLES..
6D 30 20-→ * 20 (B) TRIPLE OR MULTIPLE ROWS FIGURE 4-5. Rivet hole spacing and edge distance for single-lap sheet splices.
Par 4-57 Page 4-123
(a) DIMENSIONS FOR FORMED RIVET HEADS.
-1ž0 65D (ID MIN.) (MIN.) (=D MIN.)
(b) RIVETING TOOLS
CORRECT
INCORRECT SHAPE FOR
RIVET SNAP OR SET.
BUCKING BAR OR DOLLY.
(C) RIVET IMPERFECTIONS.
RIVET DRIVEN AT SLANT, RIVET DRIVEN RIVET FLAT ON ONE
CORRECTLY, DOLLY SIDE OR DOLLY HELD HEAD AT SLANT. FLAT.
BODY OF RIVET TOO SHORT. CLOSING HEAD RIVET NOT PULLED TIGHT, CLINCHES BULGED ON ACCOUNT RIVET TIGHT, PLATES SHAPED TOO MUCH BETWEEN PLATES, OF POOR FIT.
WITH SNAP DIE. CLOSING HEAD TOO FLAT.
RIVETED TOO MUCH. RIVET BODY CLINCHED TOO MUCH, HEAD CRACKED.
PLATES CLINCHED AT RIVET MATERIAL TOO AND DRIVEN APART. HARD WHEN RIVETING TOOL FORMED.
DAMAGED PLATE FIGURE 4-6. Riveting practice and rivet imperfections.
Par 4-57 Page 4-124
Par 4-57 Page 4-125
FIGURE 4-7. Self plugging friction-lock Cherry rivets.
Bulbed Cherrylock Rivets. One of the earlier types of mechanical-lock rivets developed were Bulbed Cherrylock blind rivets. These blind rivets have as their main advantage the ability to replace a solid shank rivet size for size. (See figure 4-8.)
A Bulbed Cherrylock consists of three parts;
a rivet shell, a puller, and a lockring. The puller or stem has five features which are activated during installation; a header, shank expanding section, lockring indent, weak or stem fracture point, and a serrated pulling stem. Carried on the pulling stem, near the manufactured head, is the stem lockring. When the rivet is pulled the action of the moving stem clamps together the sheets of metal and swells the shank to fill the drilled hole. When the stem reaches its preset limit of travel, the upper stem breaks away (just above the lockring) as the lockring snaps into the recess on the locking stem. The rough end of the retained stem in the center on the manufactured head must never be filed smooth, because it will weaken the strength of the lockring and the center stem could fall out. (See figure 4-8.)
The Bulbed Cherrylock rivets are available in two head styles: universal and 100° countersunk. Their lengths are measured in increments of 1/16 inch. It is important to select a rivet with a length related to the grip length of the metal being joined.
The Bulbed Cherrylock rivet can be installed using a G35 cherry rivet hand puller or a pneumatic Bulbed Cherrylock pulling tool.
The CherryMax (see figure 4-9) rivet uses one tool to install three standard rivet diameters and their oversize counterparts. This makes the use of CherryMax rivets very popular with many small general aviation repair shops.
CherryMax rivets are available in four nominal diameters 1/8, 5/32, 3/16, and 1/4 inch and three oversized diameters. CherryMax rivets are manufactured with two head styles, universal and countersunk. The CherryMax rivets consists of five parts; bulbed blind header, hollow rivet shell, locking (foil) collar, driving anvil, and pulling stem. The blind bulbed header takes up the extended shank and forms the bucktail on a CherryMax rivet stem. Rivet sleeves are made from 5056 aluminum, monel, and INCO 600. The stems are made from alloy steel, CRES, and INCO X-750 stem. CherryMax rivets have an ultimate shear strength ranging from 50 KSI to 75 KSI.
An Olympic-Lok (see figure 4-10) rivet is a light three-piece mechanically locked, spindle-type blind rivet. It carries its stem lock integral to the manufactured head. While installing, the lockring is pressed into a groove on the pulling stem just as the rivet completes drawing the metal together. After installation is completed, never file the stem of an Olympic-Lok rivet, because it will weaken the lockring attachment. The Olympic-Lok fastener is available in three head styles:
- STEM
STEM IS PULLED
COLLAR LOCKING BEFORE PULLING INTO RIVET SLEEVE AND STARTS TO FORM BULB BLIND HEAD BEGINS RIVET HEAD SHEET GAP > CLAMP-UP AND
HOLE FILL
ACTION BEGIN SHEAR RING
FORMATION OF BLIND
CLAMP-UP COMPLETED HEAD AND HOLE FILLING
AS STEM CONTINUES TO ARE COMPLETED
BULB OUT BLIND HEAD
SHEAR RING NOW SHEARS
FROM STEM CONE TO ALLOW
STEM TO PULL FURTHER INTO
RIVET HEAD RIVET
FIRMLY SEATED
BLIND SIDE BULB HEAD
- IS FORMED BELOW SHEAR RING GUARANTEES
MINIMUM GRIP BLIND SIDE BULBED HEAD (IN MINIMUM GRIP SHEAR
RING MAY NOT SHEAR)
SHEAR RING HAS MOVED
DOWN STEM CONE UNTIL
PULLING HEAD AUTOMATICALLY STOPS STEM BREAK NOTCH COMPLETELY INSTALLED BULBED CHERRYLOCK
FLUSH WITH TOP OF
RIVET HEAD
PULLING HEAD HAS
LOCKING COLLAR IS NOV INSERTED LOCKING
READY TO BE INSERTED COLLAR AND STEM
HAS FRACTURED FLUSH
WITH RIVET HEAD (MAXIMUM GRIP
BLIND SIDE ILLUSTRATED)
BULBED HEAD FIGURE 4-8. Mechanical-lock (Bulbed Cherrylock) Cherry rivet.
Par 4-57 Page 4-126
Par 4-57 Page 4-127
F IGURE 4-9. CherryMax rivet.
universal protruding, 100-degree flush countersink, and 100-degree flush shear; and three diameters 1/8, 5/32, and 3/16 inch. The three di ameters are available in eight different alloy combinations of 2017-T4, A-286, 5056, and monel. Olympic-Lok lock spindles are made from the same material as the sleeves.
Huck rivets (see figure 4-11) are available in two head styles, protruding and flush. They are available in four diameters 1/8, 5/32, 3/16, and 1/4 inch. Their diameters are measured in increments of 1/32 inch and lengths are measured in 1/16 inch increments. They are manufactured in three different combinations of alloys: 5056 aluminum sleeve with 2024 aluminum alloy pin, A-286 corrosion-resistant steel sleeve with an A-286 pin, and a monel 400 sleeve with an A-286 pin. The Huck fastener has the ability to tightly draw-up two or more sheets of metal together while being installed. After the take-up of the Huck fastener is completed, the lockring is squeezed into a groove on the pulling stem. The anvil or footer (of the installation tool) packs the ring into the groove of the pulling stem by bearing against the lockring.
Common pull-type Pop rivets, produced for nonaircraft related applications, are not approved for use on certificated aircraft structures or components.
Design a new or revised rivet pattern for strength required in accordance with one of the following:
The aircraft manufacturer’s maintenance manuals.
The techniques found in structural text books and using the mechanical properties found in MIL-HDBK-5.
The specific instructions in paragraphs 4-58g through 4-58n. When following the instruction in paragraphs 4-58g through 4-58n, the general rule for the diameter of the rivets used to join aluminum sheets is to use a diameter approximately three times the thickness of the thicker sheet. Do not use rivets where they would be placed in tension, tending to pull the heads off; and backup a lap joint of thin sheets with a stiffener section.
SLEEVE REDUCED INTERNAL DIAMETER TO DOUBLE
PRECISELY ALIGN THE LOCKING GROOVE TAPER DESIGN
FULLY SERRATED STEM CONTINUOUS INTEGRAL
FOR INCREMENTAL PULL-UP LOCKING COLLAR RV 1201 SERIES
COUNTERSUNK
HEAD STYLE 1/16 INCH GRIP VARIATION CAPABILITY
DESIGNED INTO FASTENER
LARGER SECOND SHANK RV 1200 SERIES FLUSH BREAKING STEM DIAMETER FOR EXTRA
PROTRUDING SLEEVE EXPANSION AND
HEAD STYLE GREAT BLIND-SIDE
BEARING AREA
GREATER LOCKING COLLAR VOLUME PROTRUDING HEAD
DRIVEN INTO LOCKING GROOVE UNDERCUT ELIMINATES
DEBURRING When the stem travel is Continued pulling breaks Olympic-Lok blind rivet is Tool jaws grip the stem and stopped by the sleeve's inter- the stem flush to the fasteninserted into a prepared pull it into the sleeve, closing nal step, the integral locking er head. Flushness is hole. Note the clearance the sheet gap, expanding the collar shears free and is assured by the positioning between the rivet and the sleeve to fill the hole, and forced into the stem locking of the break-groove when sides of the hole and the forming a consistently larger groove. This forms a stem travel is stopped by gap between the sheets. blind side bearing area. permanent mechanical lock. the sleeve's internal step.
FIGURE 4-10. Olympic-Lok rivet.
REPAIR METHODS AND PRECAUTIONS FOR ALUMINUM STRUCTURE. Carefully examine all adjacent rivets outside of the repair area to ascertain that they have not been harmed by operations in adjacent areas. Drill rivet holes round, straight, and free from cracks. Deburr the hole with an oversize drill or deburring tool.
The rivet-set used in driving the rivets must be cupped slightly flatter than the rivet head. (See figure 4-6.) Rivets are to be driven straight and tight, but not overdriven or driven while too hard, since the finished rivet must be free from cracks. Information on special methods of riveting, such as flush riveting, usually may be obtained from manufacturer's service manuals.
Splicing of Tubes. Round or streamline aluminum alloy tubular members may be repaired by splicing (See figure 4-12.) Splices in struts that overlap fittings are not acceptable. When solid rivets go completely through hollow tubes, their diameter must be at least one-eighth of the outside diameter of the outer tube.
Rivets which are loaded in shear should be hammered only enough to form a small head and no attempt made to form the standard roundhead. The amount of hammering required to form the standard roundhead often causes the rivet to buckle inside the tube. (Correct and incorrect examples of this type of rivet application are incorporated in figure 4-12.)
Par 4-57 Page 4-128
Par 4-58 Page 4-129
FIGURE 4-11. Huck rivet.
Repairs to Aluminum Alloy Members. Make repairs to aluminum alloy members with the same material or with suitable material of higher strength. The 7075 alloy has greater tensile strength than other commonly used aluminum alloys such as 2014 and 2024, but is subject to somewhat greater notch sensitivity. In order to take advantage of its strength characteristics, pay particular attention to design of parts to avoid notches, small radii, and large or rapid changes in cross-sectional areas. In fabrication, exercise caution to avoid processing and handling defects, such as machine marks, nicks, dents, burrs, scratches, and forming cracks. Cold straightening or forming of 7075-T6 can cause cracking; therefore, it may be advisable to limit this processing to minor cold straightening.
Wing and Tail Surface Ribs. Damaged aluminum alloy ribs either of the stam ped sheet-metal type or the built-up type employing special sections, square or round tubing, may be repair ed by the addition of suitable reinforcement. (A cceptable methods of repair are shown in figures 4-13 and 4-14.) These examples deal with types of ribs commonly found in small and medium size aircraft. Repair schemes developed by the aircraft manufacturer are acceptable, but any other methods of reinforcement are major repairs and require approved data.
Trailing and Leading Edges and Tip Strips. Repairs to wing, control surface tra iling edges, leading edges, and tip strips should be made by properly executed and reinforced splices. Acceptable methods of trailing edge repairs are shown in figure 4-15.
Repair of Damaged Skin. In cases where metal skin is damaged extensively, repair by replacing an entire sheet panel from one structural member to the next. The repair seams are to lie along stiffening members, bulkheads, etc.; and each seam must be made exactly the same in regard to rivet size, splicing, and rivet pattern as the manufactured seams at the edges of the original sheet. If the tw o manufactured seams are different, the stronger one will be copied. (See figure 4-16 for typical acceptable methods of repairs.)
Patching of Small Holes. Small holes in skin panels which do not involve damage to the stiffening members may be patched by covering the hole with a patch plate in the manner shown in figure 4-16. Flush patches also may be installed in stressed-skin type construction. An acceptable and easy flush patch may be made by trimming out the damaged area and then installing a conventional patch on the underneath side or back of the sheet being repaired. A plug patch plate of the same size and skin thickness as the opening may then be inserted and riveted to the patch plate. Other types of flush patches similar to those used for patching plywood may be used. The rivet pattern used, however, must follow standard practice to maintain satisfactory strength in the sheet.
Splicing of Sheets. The method of copying the seams at the edges of a sheet may not always be satisfactory.
For example, when the sheet has cutouts, or doubler plates at an edge seam, or when other members transmit loads into the sheet, the sp lice must be designed as illustrated in the following examples.
Material: Clad 2024 sheet, 0.032 inch thickness. Width of sheet (i.e., length at splice) = “W” = 10 inches.
Determine rivet size and pattern for a single-lap joint similar to figure 4-5.
Use rivet diameter of approximately three times the sheet thickness, 3 x 0.032 = 0.096-inch. Use 1/8-inch
Par 4-58 Page 4-130 2117-T4 (AD) rivets (5/32-inch 2117-T4 (AD) would be satisfactory).
Use the number of rivets required per inch of width “W” from table 4-9 (read NOTES) (number per inch 6.2 x .75 = 4.6 or the total number of rivets required = 10 x 4.6 or 46 rivets.)
Lay out rivet pattern with spacing not less than shown in figure 4-5. Referring to figure 4-5(A), it seems that a double row pattern with the minimum spacing will give a total of 50 rivets. However, as only 46 rivets are required, two rows of 23 rivets each equally spaced over the 10 inches will result in a satisfactory splice.
Straightening of Stringers or Intermediate Frames .
Members which are slightly bent may be straightened cold and examined with a magnifying glass for cracks or tears to the material. Reinforce the straightened part to its original shape, depending upon the condition of the material and the magnitude of any remaining kinks or buckles. If any strain cracks are apparent, make complete reinforcement in sound metal beyond the damaged portion.
Local Heating. Do not apply local heating to facilitate bending, swaging, flatteni ng, or expanding operations of heat-treated aluminum alloy members, as it is difficult to control the temperatures closely enough to prevent possible damage to the metal, and it may impair its corrosion resistance.
Splicing of Stringers and Flanges. It is recommended that all splices be made in accordance with the manufacturer’s recommendations. If the manufacturer’s recommendations are not available, the typical splices for various shapes of sections are shown in figures 4-17 through 4-19. Design splices to carry both tension and compression, and use the splice shown in figure 4-18 as an example illustrating the following principles.
To avoid eccentric loading and consequent buckling in compression, place splicing or reinforcing parts as symmetrically as possible about the centerline of the member, and attach to as many elements as necessary to prevent bending in any direction.
To avoid reducing the strength in tension of the original bulb angle, the rivet holes at the ends of the splice are made small (no larger than the original skin attaching rivets), and the second row of holes (those through the bulbed leg) are staggered back from the ends. In general, arrange the rivets in the splice so that the design tensile load for the member and splice plate can be carried into the splice without failing the member at the outermost rivet holes.
•L = 20 SPACES 3 d EACH - -TOTAL NO. OF RIVETS - 18 (9 EACH SIDE OF SPLICE) A = ORIGINAL TUBE C = REPLACEMENT TUBE B = SLEEVE USE 2117-T ALUM. ALLOY RIVETS SMALL HEAD
HAMMER STANDARD SPLICES MAY BE USED ON LIGHTLY- 2dl ROUND HEAD LONGERONS OR WEB MEMBERS.
CORRECT WAY INCORRECT WAY d MUST NOT BE LESS THAN D/8.
R = 3 d
•0 30
• •. .00 100
STREAMLINE M/3 EACH (USE BASIC ROUND SIZES IN TABLE FOR SIZE OF RIVETS ETC.)
A, C * 3/4 718 1 1-1/8 1-1/4 1-/3/8 1-1/2 1-/5/8 1-3/4 1-718 .065 065 .065 .065 .058 .058 .058 .058 .058 .058 718 1-1/8 1-1/4 1-3/8 1-1/2 1-5/8 1-3/4 1-7/8 2 ALL .058 THICK RIVET DIA. 5/32 5/32 3/16 3/16 3/16 3/16 1/4 1/4 1/4 1/4 L 9-3/8 9-3/8 11-1/4 11-1/4 11-1/4 11-1/4 15 15 15 15 * INCLUDES ALL THICKNESSES UP TO AND INCLUDING MAXIMUM SHOWN.
NOTE. USE SAME MATERIAL AS ORIGINAL FOR SLEEVE AND REPLACEMENT TUBE.
FIGURE 4-12. Typical repair method for tubular members of aluminum alloy.
Par 4-58 Page 4-131
- D
- A D- 30 3030.202030.30.300
AT LEAST AS THICK
AS ORIGINAL
ORIGINAL
REINFORCEMENT 2117-AD RIVETS MATERIAL - DURAL. OR ALUMINUM ALLOY USED IN 3/32" DIA. MIN.
ORIGINAL CONSTRUCTION.
SCALE - TWICE SIZE SECTION A-A
SCALE - TWICE SIZE 2017-T3
000.0000 D SQ. ROD 3D 3D 3D 3D 130|30, 30 30 130„ • 2117-AD RIVETS 1/8" DIA: MIN.
NOTE: FOR MINIMUM NUMBER OF RIVETS REQUIRED, SEE PARAGRAPH 4-58g AND SUBSEQUENT.
FIGURE 4-13. Typical repair for buckled or cracked metal wing rib capstrips.
Par 4-58 Page 4-132
SEE (C) SEE (D) 000OT0 (A)
- SEE (E) (B) D = RIVET DIA.
›PROX.) (MINIMUM 3/32) +0 * BEND RADII TO FIT
ORIGINAL RIB.
(G) 1ĞPLYWOODTO STIFFEN BENT RIBS.
MACHINE SCREW D OR RIVET.
1.5 ₺ (APPROX.)
<PEEN (E) 2030. 30.202015980.39 (D) NOTE: FOR MINIMUM NUMBER OF RIVETS REQUIRED, SEE PARAGRAPH 4-58g AND SUBSEQUENT.
FIGURE 4-14. Typical metal rib repairs (usually found on small and medium-size aircraft).
Par 4-58 Page 4-133
"A" .040" 2017-T3 SPACER 2D, 3D 30 202D 3D 3D 20 "B" 2024-T3 SPLICE BAR "Д" * В" ----+1 2117-AD RIVETS 3/32" DIA. MIN.
- CRACK 2117-AD RIVETS 3/32" DIA. MIN.
- ЗА ЗА I. STRAIGHTEN CRIMPED OVER PORTION. CRACK
2. INSERT HARDWOOD (ASH) INSERT SHAPED.
TO CONFORM TO T.E. PIECE.
2117-AD RIVETS 2D 20 20 2D D 3/32" DIA. MIN.
FLATTEN HEADS (APPROX. 1.5 ₺ ) OUTSIDE I. STRAIGHTEN CRIMPED PORTION. - GRACK
2. USE SAME AL. ALLOY AS IN ORIGINAL.
NOTE: FOR MINIMUM NUMBER OF RIVETS REQUIRED, SEE PARAGRAPH 4-58g AND SUBSEQUENT.
FIGURE 4-15. Typical repairs of trailing edges.
Par 4-58 Page 4-134