Par 7-165 Page 7-333 (and 7-42)
SECTION 9. TURNBUCKLES
GENERAL. A turnbuckle is a device used in cable systems to provide a means of adjusting tension. Turnbuckles have barrel-shaped sleeves with internal left- and right-hand threads at opposite ends. The cables, with terminals attached, are made to such a length that, when the turnbuckle is adjusted to give the specified cable tension, a sufficient number of threads on the terminal ends are screwed into the barrel to hold the load. The cliplocking turnbuckle and its associated parts are identical to standard AN and MS parts except for a slot grooved on the interior of the barrel and the shanks of the forks, eyes, etc. The clip-locking turnbuckle parts have the following drawing numbers: MS21251, turnbuckle body;
MS21252, turnbuckle clevis end; MS21253, turnbuckle clevis end (for bearing); NAS649 and NAS651, turnbuckle clip; MS21254 and NAS648, turnbuckle eye (for pin); MS21255 and NAS647, turnbuckle eye end (for wire rope);
NAS645 and NAS646, turnbuckle fork;
MS21256, turnbuckle barrel locking clip;
AN130-170, turnbuckle assemblies; and, MS21259 and MS21260, terminal, wire rope, stud.
NOTE: Turnbuckles showing signs of thread distortion/bending should be replaced.
Turnbuckle ends are designed for providing the specified cable tension on a cable system, and a bent turnbuckle would place undesirable stress on the cable, impairing the function of the turnbuckle.
TURNBUCKLE INSTALLATION. (See figure 7-23.) When installing cable system turnbuckles, it is necessary to screw both threaded terminals into the turnbuckle barrel an equal amount. It is essential that turnbuckle terminals be screwed into the barrel so that not more than three threads on the terminal are exposed. (See figure 7-23A.) On initial installation, the turnbuckle terminals should not be screwed inside the turnbuckle barrel more than four threads. (See figure 7-23B.)
FIGURE 7-23. Turnbuckle thread tolerance.
WITNESS HOLE. Some manufacturers of turnbuckles incorporate a “witness hole,” in the turnbuckle barrel to ensure that the threaded cable terminals are screwed in far enough into the barrel. The “witness hole” can be inspected visually, or by using a piece of safety wire as a probe.
7-168.7-178. [RESERVED.]
Par 7-179 Page 7-334
SECTION 10. SAFETY METHODS FOR TURNBUCKLES
GENERAL. Safety all turnbuckles with safety wire using either the double or single-wrap method, or with any appropriately approved special safetying device complying with the requirements of FAA Technical Standard Order TSO-C21. The swaged and unswaged turnbuckle assemblies are covered by AN standard drawings. Do not reuse safety wire.
Adjust the turnbuckle to the correct cable tension so that no more than three cable threads are exposed on either side of the turnbuckle barrel.
DOUBLE-WRAP METHOD. Of the methods using safety wire for safetying turnbuckles, the method described here is preferred, although either of the other methods described is satisfactory. The method of double-wrap safetying is shown in figure 7-24(A).
Use two separate lengths of wire. Run one end of the wire through the hole in the barrel of the turnbuckle and bend the ends of the wire toward opposite ends of the turnbuckle.
Pass the second length of the wire into the hole in the barrel and bend the ends along the barrel on the side opposite the first. Spiral the two wires in opposite directions around the barrel to cross each other twice between the center hole and the ends.
Then pass the wires at the end of the turnbuckle in opposite directions through the hole in the turnbuckle eyes or between the jaws of the turnbuckle fork, as applicable, laying one wire along the barrel and wrapping the other at least four times around the shank of the turnbuckle and bindi ng the laid wires in place before cutting the wrapped wire off.
Wrap the remaining length of safety wire at least four turns around the shank and cut it off. Repeat the procedure at the opposite end of the turnbuckle.
When a swaged terminal is being safetied, pass the ends of both wires through the hole provided in the terminal for this purpose and wrap both ends around the shank as previously described. If the hole is not large enough to allow passage of both wires, pass the wire through the hole and loop it over the free end of the other wire, and then wrap both ends around the shank as previously described. Another satisfactory double-wrap method is similar to the previous method, except that the spiraling of the wires is omitted as shown in figure 7-24(B).
SINGLE-WRAP METHOD. The single-wrap methods described in the following paragraphs and as illustrated in figure 7-24(C) and (D) are acceptable, but are not the equal of the doublewrap methods.
Pass a single length of wire through the cable eye or fork, or through the hole in the swaged terminal at either end of the turnbuckle assembly. Spiral each of the wire ends in opposite directions around the first half of the turnbuckle barrel, so as to cross each other twice.
Thread both wire ends through the hole in the middle of the barrel so that the third crossing of wire ends is in the hole, again, spiral the two wire ends in opposite directions around the remaining half of the turnbuckle, crossing them twice. Then, pass one wire end through the cable eye or fork, or through the hole in the swaged terminals, in the manner previously described. Wrap both wire ends around the shank for at least four turns each, cutting off excess wire. This method is shown in figure 7-24(C).
Par 7-179 Page 7-335
F IGURE 7-24. Safetying turnbuckles.
For the method shown in figure 7-24D, pass one length of wire through the center hole of the turnbuckle and bend the wire ends toward opposite ends of the turnbuckle. Then pass each wire end through the cable eye or fork, or through the hole in the swaged terminal, and wrap each wire around the shank for at least four turns, cutting off excess wire. After safetying, no more than three threads of the turnbuckle threaded terminal should be exposed.
SAFETY-WIRE SECURED TURNBUCKLES. (See figure 7-25.) Before securing turnbuckles, threaded terminals should be screwed into the turnbuckle barrel until no more than three threads of either terminal are outside the barrel. After the turnbuckle has been adjusted for proper cable tension, two pieces of safety wire are inserted, half the wire length into the hole in the center of the turnbuckle barrel. The safety-wires are bent so that each wire extends half the length of the turnbuckle on top and half on bottom. The ends of the wires are passed through the hole in the turnbuckle eyes or between the jaws of the turnbuckle fork, as applicable. The wires are then bent toward the center of the turnbuckle and each wire is wrapped around the shank four times, binding the wrapping wires in place as shown in figure 7-25.
When a swaged terminal is being secured, one wire is passed through the hole in the terminal and is looped over the free end of the other wire and both ends wrapped around the shank. All lock wire used in the safetying of turnbuckles should be carbon steel, corrosion-resistant steel, ni ckel-chromium iron alloy (inconel), nickel-copper alloy (monel) or aluminum
Par 7-182 Page 7-336 alloy. For safety cable diam eter of safety wire size and material, refer to table 7-8.
Care should be exercised when safety wiring, particularly where corrosion will present a problem, because smaller wire sizes tend to crack when twisted.
TABLE 7-8. Turnbuckle safetying guide.
Cable Size Type of Wrap Diameter of Safety Wire Material (Annealed Condition) 1/16 Single 0.040 Copper, brass.
3/32 Single 0.040 Copper, brass.
1/8 Single 0.040 Stainless steel, Monel and “K” Monel.
1/8 Double 0.040 Copper, brass.
1/8 Single 0.057 min. Copper, brass.
5/32 and greater.
Double 0.040 Stainless steel, Monel and “K” Monel.
5/32 and greater Single 0.057 min. Stainless steel, Monel or “K” Monel.
5/32 and greater Double 0.0512 Copper, brass.
1 Galvanized or tinned steel, or soft iron wires are also acceptable.
SPECIAL LOCKING DEVICES. Several turnbuckle locking devices are available for securing turnbuckle barrels such as wirelocking clips. Persons intending to use a special device must ensure the turnbuckle assembly has been designed to accommodate such devices. A typical unit is shown in figure 7-26. When special locking devices are not readily available, the use of safety wire is acceptable.
ASSEMBLING AND SECURING CLIP-LOCKING TURNBUCKLES. (See table 7-9 and figure 7-27.) Wire clip-locking turnbuckles are assembled and secured in the following ways.
Engage threads of turnbuckle barrel with threads of cable terminal and turn barrel until proper cable tension is reached.
Align slot in barrel with slot in cable terminal.
Hold lock clip between thumb and forefinger at loop end and insert straight end of clip into opening formed by aligned slots.
Bring hook end of lock clip over hole in center of turnbuckle barrel and seat hook loop into hole.
Apply pressure to hook shoulder to engage hook lip in turnbuckle barrel and to complete safety locking of one end of turnbuckle.
NOTE: Repeat the above steps to safety lock the opposite end of turnbuckle. Both lock clips may be inserted in the same turnbuckle barrel hole or they may be inserted in opposite holes. Howe ver, do not reverse wire locking clips
- TURNBUCKLE FORK •TURNBUCKLE -WRAP, FOUR TURNS - CABLE
SAFETY WIRE BARREL
WRAP, FOUR TURNS TURNBUCKLE EYE -THIMBLE
SAFETY WIRE WRAP, FOUR TURNS титаний
- SWAGED TERMINAL FIGURE 7-25. Securing turnbuckles.
TURNBUCKLE BODY- LOCKING-CLIP MS21251 MS21256 FIGURE 7-26. Clip-type locking device.
Par 7-182 Page 7-337
Par 7-184 Page 7-338 (and 7-48) TABLE 7-9. Locking-clip application.
NOMINAL CABLE DIA.
THREAD UNF-3
LOCKING CLIP MS21256
TURNBUCKLE BODY MS21251 1/16 No. 6-40 -1 -2S 3/32 No. 10-32 -3S -2 -3L 1/8 -1 -4S 1/4-28 -2 -4L 5/32 -1 -5S -2 -5L 3/16 5/16-24 -1 -6S -6L 7/32 3/8-24 -2 -7L 1/4 -8L 9/32 7/16-20 -3 -9L 5/16 1/2-20 -10L
FIGURE 7-27. Assembling and securing clip-locking turnbuckles
7-185.7-195. [RESERVED.]
Par 7-196 Page 7-339
SECTION 11. HARDWARE IDENTIFICATION TABLES
TABLE 7-10. TABLE OF RIVETS.
Rivet Number Description AN427 Rivet, 100ºcsk. Head steel, monel, copper AN430 Rivet, round head al. Alloy AN441 Rivet, tinners Head, steel, ss, monel AN456 Rivet, brazier head, aluminum alloy AN123151-123750
Rivet, universal head & 100º steel, Inconel NAS 1200 Rivet, solid, 100º flush shear head NAS 1241 Rivet, solid, 100º flush head NAS 1242 Rivet, solid universal head NAS 1398 Rivet, blind, protruding head, locked spindle NAS 1399 Rivet, blind, 100º csk.
Head, locked spindle
TABLE 7-10. (CONTINUED) Rivet Number Description NAS 1738-1739 Rivet, blind, protruding & flush hd., mech.
locked spindle, bulbed NAS1806-1816 Rivet, hi-shear, flathead., ti. alloy NAS1906-1916 Rivet, hi-shear, 100° hd., ti. alloy AN124951-125550 Rivet, solid universal head & 100° csk. head, cres. steel, inconel AN125551-1255700 Rivet, solid universal head, steel AN426 MS20426 Rivet, solid, csk. 100° head al. alloy AN470 MS20470 Rivet, solid, universal head, al. & al. alloy MS9319 Rivet, solid univ. head, AMS 7233 MS9403 Rivet, solid, universal head, AMS 5737 MS16535 Rivet, tubular, oval head
Par 7-196 Page 7-340 TABLE 7-10. (CONTINUED) Rivet Number Description MS16536 Rivet, tubular, 100° flat csk. head MS20426 Rivet, solid, csk., 100° al. alloy MS20427 Rivet, solid, csk., 100° flush hd., AMS 7233 MS20470 Rivet, solid, universal head, al. alloy MS20600 Rivet, blind, pull stem, protruding head MS20601
Rivet, blind, pull stem, 100°, flush head MS20602-20603 Rivet, blind, explosive MS20604-20605 Rivet, blind nonstructural univ.
and 100° flush head MS20613-20615 Rivet, solid, monel, universal hd., steel, ss, brass, copper NAS452-453 Rivnut, 100° csk. head & flathead NAS454-455 Rivet blind, al. alloy
TABLE 7-10. (CONTINUED) Rivet Number Description NAS508 Rivet, universal head, monel NAS1054 Rivet, hi-shear, protruding head NAS1055 Rivet, hi-shear, 100° flush head NAS1097 Rivet, solid, 100° flush shear head, al. Alloy NAS1198 Rivet, solid, universal head NAS1199 Rivet, solid, 100° flush head
TABLE 7-11. TABLE OF SCREWS.
Screw MS, AN, or NAS Number Description AN255 Screw, external relieved body AN500 & 501 Screw, machine fillister head AN502 & 503 Screw, machine, fill. Head, drilled, coarse & fine AN504 Screw, tapping, thread cutting rnd.
Head, mach. Thread
Par 7-196 Page 7-341 TABLE 7-11. (CONTINUED) Screw MS, AN, or NAS Number Description AN505 Screw, machine, flathead, 82° coarse thread AN506 Screw, tapping, type F, coarse & fine AN507 Screw, machine, flathead, 100° AN508 Screw, machine, round head AN509 Screw machine, 100° structural AN510 Screw, machine, flathead, 82° fine thread AN515 & AN520 Screw, machine, round head AN525 Screw, washer head AN526 Screw, machine buttonhead AN530 Screw-tapping, thread cutting, rnd. hd.
AN531 Screw, tapping, thread forming or cutting, 82° flathead.
TABLE 7-11. (CONTINUED) Screw MS, AN, or NAS Number Description AN535 Drive screw, round head AN545 Screw, wood, round head AN550 Screw, wood, flathead, 82° AN565 Setscrew, hex. & fluted socket AN115401-115600 Screws, flat fill. head, steel, .190-.375 AN115601-115800 Drilled shank Screw flat fill. head, steel, .190-.375 AN115801-116150 Screw, flat fill. head, steel. .190-.375 AN116901-117080 Screw, oval fill. head, steel MS9016 Bushing Screw, plain MS9017 Bushing Screw, slotted MS9122-9123
Screw, machine slotted hex.
hd.
Par 7-196 Page 7-342 TABLE 7-11. (CONTINUED) Screw MS, AN, or NAS Number Description MS9177-9178 Screw, dbl. hex. head, cres.
MS9183-9186 Screw, machine, steel, drilled 12 pt. hd., cad. plate MS9187-9188 Screw, drilled dbl. hex. head, cres.
MS9189-9192 Screw, machine, steel, 12 pt. hd., black oxide MS9206-9214 Screw, dbl. hex. ext. washer head, diffused nickel cad. plate MS9215-9223 Screw, dbl. hex. ext.
washer head, diffused nickel cad. plate, drilled MS9281-9291 Screw, machine, hex.
hd., AMS 6322 black oxide MS9292-9302 Screw, machine, hex. hd., AMS 6322 blk. oxide, drilled MS9316-9317 Screw, machine, steel slotted hex. head MS9438-9439 Screw, mach. steel AMS 6304 diffused nickel cad. hex. hd., one hole MS9631-9639 Screw, mach., hex. hd.
one hole, full shank, titanium AMS 4967 TABLE 7-11. (CONTINUED) Screw MS, AN, or NAS Number Description MS16198 Screw, wood, slotted RH austenitic corr. res.
steel MS16199 Screw, wood, slot flathead, copper silicone MS16995 Screw, cap, socket head hex., corr.
resisting steel UNC-3A MS16996 Screw, cap, socket head, hex., corr.
resisting steel UNF-3A MS16997 Screw, cap, socket head, hex., alloy steed cad. UNC-3A MS16998 Screw, cap, socket head, hex., alloy steel, cad. UNF-3A MS18063-18068 Setscrew, self-locking, cup, flat, cone pts., steel & stainless MS18211 Screw, machine, flathead, plastic, nylon MS18212 Screw, machine, panhead, plastic, nylon MS21090 Screw, self-lock, panhead, cross recessed MS21207 Screw, tapping, 100° clk. flathead., steel, cres. steel
Par 7-196 Page 7-343 TABLE 7-11. (CONTINUED) Screw MS, AN, or NAS Number Description MS21262 Screw, self-lock, int. wrenching MS21277-21285 Screw, machine, double hex., ext.
washer head MS21286-21294 Screw, machine, double hex., ext.
washer head MS21295 Screw, self-lock, int. wrenching MS21318 Screw, drive, round head, Type U MS21342 Setscrew, fluted socket, cup and flat point MS24615-24618 Screw, tapping, phillips recessed, pan & 82° flathead Type A MS24619-24622 Screw, tapping, phillips recessed, pan & 82° flathead Type B MS24623-24626 Screw, tapping, cross recessed pan & 82° flathead, Type BF or BT MS24627-24630 Screw, tapping, thread cutting cross recessed pan & 82° flathead, Type F MS24667 & 24671 Screw, cap socket hd., flat, csk.
TABLE 7-11. (CONTINUED) Screw MS, AN, or NAS Number Description MS24673-24678 Screw, cap socket hd., flat, drilled MS24693 Screw, machine, flat csk. head, 100° cross recess MS24694 Screw, machine, csk. flathead., 100° cross recess, structural MS27039 Screw, machine, panhead, structural, cross recessed MS35190-35203 Screw, machine 82° flathead., cross recessed, steel, brass, alum.
MS35206-35219 Screw, machine, panhead, cross recessed, steel, brass, alum.
MS35223-35234 Screw, machine, panhead, slotted, SS steel, steel MS35239-35243 Screw, machine, flathead., slotted, steel MS35265-35278 Screw, machine, drilled fillister head, slotted, SS steel, brass, alum.
MS35492-35493
Screw, wood, flathead, cross recessed MS35494-35495 Screw. wood, flat & round hd., slotted
Par 7-196 Page 7-344 TABLE 7-11. (CONTINUED) Screw MS, AN, or NAS Number Description MS35914 Insert, screw, thread, self-tapping MS51017-51047 Setscrew, hex. socket SS & steel half dog, cone, flat, cup pt.
MS51861 Screw, tapping, type AB, panhead, cross recessed MS51862 Screw, tapping, type AB, flathead., cross recessed MS51957-51958 Screw, machine, panhead, cross recessed MS51959-51960 Screw, machine, flathead, cross recessed MS51963-51966 Setscrew, hex. socket, cup & flat point MS51973-51974 Setscrew, hex. socket, cone point MS51975 Screw, shoulder, socket head MS51976-51977 Setscrew, hex. socket, half dog point MS51981-51982 Setscrew, hex. socket, oval point TABLE 7-11. (CONTINUED) Screw MS, AN, or NAS Number Description NAS220-237 Screw, brazier hd.
phillips recessed NAS384-385 Screw, oval head, phillips recessed 100°, 82°, steel NAS387-388 Screw, machine, oval hd., 100°, 82°, steel NAS514 Screw, machine, 100° flathead., fully threaded, al. steel NAS517 Screw, 100° flathead, close tol. 160,000 psi NAS548 Screw, 100° flathead, type B tapping NAS560 Screw, machine, 100° structural, hi-temp NAS600-606 Screw, machine, aircraft, panhead phillips recessed, full thr., steel NAS608-609 Screw, hex. socket cap, plain & selflocking, drilled head NAS623 Screw, panhead. thr.
short, 160,000 psi NAS720 Screw, panhead, assembled