Par 7-167 Page 7-48
7-167. 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 7-49 SECTION 10. SAFETY METHODS FOR TURNBUCKLES
7-179. 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, Aircraft Turnbuckle Assemblies and/or Turnbuckle Safetying Devices. 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.
7-180. 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, image (A).
FIGURE 7-24. SAFETYING TURNBUCKLES
Par 7-180 Page 7-50
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.
b. 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.
c. 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 binding the laid wires in place before cutting the wrapped wire off.
d. 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.
e. 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, image (B).
7-181. SINGLE-WRAP METHOD. The single-wrap methods described in the following paragraphs and as illustrated in Figure 7-24, images (C) and (D) are acceptable, but are not the equal of the double-wrap methods.
a. 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, image (C).
b. For the method shown in Figure 7-24, image (D), 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.
7-182. 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
Par 7-182 Page 7-51 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.
FIGURE 7-25. SECURING TURNBUCKLES
a.
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, nickel-chromium iron alloy (Inconel), nickel-copper alloy (Monel), or aluminum alloy. For safety cable diameter of safety wire size and material, see Table 7-8.
b. 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 Double 0.020 Stainless steel, Monel, and “K” Monel.1 1/16 Single 0.040 Copper, brass.1 3/32 Single 0.040 Copper, brass.1 1/8 Single 0.040 Stainless steel, Monel, and “K” Monel.
1/8 Double 0.040 Copper, brass.1 1/8 Single 0.057 min. Copper, brass.1 5/32 and greater Double 0.040 Stainless steel, Monel, and “K” Monel.1
Par 7-183 Page 7-52 Cable Size Type of Wrap Diameter of Safety Wire Material (Annealed Condition) 5/32 and greater Single 0.057 min. Stainless steel, Monel, or “K” Monel.1 5/32 and greater Double 0.0512 Copper, brass.1 1 Galvanized or tinned steel, or soft iron wires are also acceptable.
7-183. SPECIAL LOCKING DEVICES. Several turnbuckle locking devices are available for securing turnbuckle barrels such as wire-locking 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.
FIGURE 7-26. CLIP-TYPE LOCKING DEVICE 7 -184. 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.
a. Engage threads of turnbuckle barrel with threads of cable terminal and turn barrel until proper cable tension is reached.
b. Align slot in barrel with slot in cable terminal.
c. Hold lock clip between thumb and forefinger at loop end and insert straight end of clip into opening formed by aligned slots.
d. Bring hook end of lock clip over hole in center of turnbuckle barrel and seat hook loop into hole.
e. 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. However, do not reverse wire locking clips.
Par 7-184 Page 7-53 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 1/4-28 -1 -4S -2 -4L 5/32 -1 -5S -2 -5L 3/16 5/16-24 -1 -6S -2 -6L 7/32 3/8-24 -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.]
SECTION 11. HARDWARE IDENTIFICATION TABLES TABLE 7-10. TABLE OF RIVETS Rivet Number Description Rivet Number Description AN427 Rivet, 100 csk. Head NAS 1738-1739 Rivet, blind, protruding steel, monel, copper & flush hd., mech.
locked spindle, bulbed AN430 Rivet, NAS1806-1816 Rivet, hi-shear, round head al. Alloy O flathead., ti. alloy AN441 Rivet, tinners Head, NAS1906-1916 Rivet, hi-shear, steel, ss, monel 100° hd., ti. alloy AN456 Rivet, brazier head, AN124951-125550 Rivet, solid universal aluminum alloy head & 100° csk. head, cres. steel, inconel AN123151-123750 Rivet, universal head & AN125551-1255700 Rivet, solid universal 100• steel, Inconel head, steel NAS 1200 shear head Rivet, solid, 100• flush AN426 MS20426 TOO head al. alloy Rivet, solid, csk. 100° NAS 1241 head Rivet, solid, 100• flush AN470 MS20470 head, al. & al. alloy Rivet, solid, universal MS9319 Rivet, NAS 1242 Rivet, solid universal solid univ. head, head AMS 7233 NAS 1398 Rivet, blind, protruding MS9403 Rivet, solid, universal head, head, locked spindle AMS 5737 MS16535 Rivet, tubular, NAS 1399 Rivet, blind, 100• csk. oval head Head, locked spindle Par 7-195 Page 7-54
TABLE 7-10. TABLE OF RIVETS (CONTINUED) Rivet Number Description Rivet Number Description MS16536 Rivet, tubular, NAS508 Rivet, 100° flat csk. head universal head, monel MS20426 Rivet, solid, csk., NAS1054 Rivet, hi-shear, O 100° al. alloy protruding head MS20427 Rivet, solid, csk., NAS1055 Rivet, hi-shear, 100° flush hd., 100° flush head AMS 7233 MS20470 Rivet, solid, NAS1097 Rivet, solid, 100° flush universal head shear head, al. Alloy al. alloy MS20600 Rivet, blind, NAS1198 Rivet, solid, pull stem, universal head protruding head MS20601 Rivet, blind, pull stem, NAS1199 Rivet, solid, 100°, flush head 100° flush head MS20602-20603 Rivet, blind, explosive MS20604-20605 Rivet, blind nonstructural univ.
and 100° flush head MS20613-20615 Rivet, solid, monel iniversal nd., steel ss, brass, copper NAS452-453 Rivnut, 100° csk. head & flathead NAS454-455 Rivet blind, al. alloy Par 7-195 Page 7-55
TABLE 7-11. TABLE OF SCREWS Screw MS, AN, or Description Screw MS, AN, or Description NAS Number NAS Number AN255 Screw, AN505 Screw, machine, external relieved body flathead, 82° coarse thread AN500 & 501 Screw, AN506 Screw, tapping, machine fillister head type F, coarse & fine AN502 & 503 Screw, AN507 Screw, machine, machine, fill. Head, flathead, 100° drilled, coarse & fine AN504 thread cutting rnd. Screw, tapping, AN508 round head Screw, machine, Head, mach. Thread 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.
Par 7-195 Page 7-56
TABLE 7-11. TABLE OF SCREWS (CONTINUED) Screw MS, AN, or Description Screw MS, AH, or Description NAS Number NAS Humber AN535 Drive screw, M S9177-9178 Screw, round head dbl. hex. head, cres.
AN545 Screw, wood, MS9183-9186 Screw, machine, steel, round head drilled 12 pt. hd., cad. plate AN550 Screw, wood, MS9187-9188 Screw flathead, 82° drilled dbl. hex. head, cres.
AN565 hex. & fluted socket Setscrew, M S9189-9192 Screw, machine, steel, 12 pt. ho., black oxide AN115401-115600 Screws, flat fill. head, M S9206-9214 Screw, steel, 190-375 dbl. hex, ext. washer head, diffused nickel cad. plate AN11 5601-115800 Drilled shank Screw flat fill. head, steel, M S9215-9223 Screw, dal. hex. ext.
.190-375 washer head, diffused nickel cad. plate, drilled AN115801-116150 Screwi flat fill. head, M S9281 -9291 Screw, machine, hex steel. .190-.375 hd., AMS 6322 black oxide AN116901-117080 Screw oval fill. head, steel M S9292-9302 Screw, machine, hex. hd., AMS 6322 blk. oxide, drilled M S9016 Bushing Screw, plain M S9316-9317 Screw, machine, steel slotted hex. head M S9017 Bushing Screw, slotted M S9438-9439 Screw mach. steel AMS 6304 diffused nickel cad. hex. ho., M S9122-9123 Screw; one hole machine slotted hex. M S9631-9639 Screw; mach., hex. hd.
hd. one hole, full shank, titanium AM S 4967 Par 7-195 Page 7-57
TABLE 7-11. TABLE OF SCREWS (CONTINUED) Screw MS, AH, or Description Screw MS, AN, or Description HAS Humber NAS Number MS16198 Screw, wood, slatted MS21 262 Screw, selfłock, RH austenitic corr. res. int. wenching steel MS16199 Screw, wood, slot flat- MS21 277-21285 Screw, machine, douhead, copper silicone ble hex., ext. washer фици head MS16995 Screw, cap, socket MS21 286-21294 Screw, machine, douhead hex., corr. resist- ble hex., ext. washer ing steel UNC-34 head MS16996 Screw, cap, socket MS21 295 Screw; self-ock, head, hex., corr. re- int. wrenching sisting steel UNF -34 MS16997 Screw, cap, socket MS21318 screw drive, head, hex., alloy steed round head, cad. UNC-34 Type U MS16998 Screw; cap, socket MS21 342 Setscrew head, hex., alloy steel, fluted socket, cad. UNF -34 cup and flat point MS18063-18068 Setscrew, self-locking, MS24615-24618 Screw, tapping, phillips cup, flat, cone pts., recessed, pan 8 82° steel & stainless fathead Type A MS18211 Screw, machine, flat- MS24619-24622 Screw, tapping, phillips head, plastic, nylon IT recessed, pan 8 82° fathead Type B MS18212 Screw, machine, pan- MS24623-24626 Screw, tapping, cross head, plastic, nylon recessed pan & 82° fathead, Type BF or MS21090 Screw, self-lock, pan- MS24627-24630 Screw, tapping, thread head, cross recessed cutting cross recessed pan & 82° fathead, Type F MS21 207 Screw tapping, MS24667 8 24671 Screw, cap socket ho., 100° clk. flathead., flat, csk.
steel, cres. steel Par 7-195 Page 7-58
TABLE 7-11. TABLE OF SCREWS (CONTINUED) Screw MS, AN, or Description Screw MS, AN, or Description NAS Humber NAS Number M S2467 3-24678 Screw, cap socket hd., M S35914 Insert, screw, thread, flat, drilled self-tapping M S24693 Screw, machine, M S51017-51047 Setscrew, hex. socket flat csk. head, 100° SS & steel half dog, cross recess cone, flat, cup pt.
M S24694 Screw, machine, M S51861 Screw, tapping, type csk. fathead., 100% AB, panhead, cross recross recess, structural cessed M S27039 Screw, machine, MS51862 Screw, tapping, type panhead, structural, AB, flathead., crossrecross recessed cessed M S35190-35203 Screw, machine 82° MS51957-51958 Screw, machine, panflathead., cross re- head, cross recessed cessed, steel, brass, alum .
M S35206-35219 Screw, machine, pan- MS51959-51960 Screw, machine, flathead, cross recessed, head, cross recessed steel, brass, alum.
M S35223-35234 head, slotted, SS steel, Screw, machine, pan- MS51963-51966 Setscrew; hex. socket, cup & flat point ste el MS35239-35243 Screw, machine, flat- M S51973-51974 Setscrew, hex. socket, head., slotted, steel cone point M S35265-35278 Screw, machine, drilled fillister head, slotted, SS seel, brass, alum. MS51975 Screw, shoulder, socket head M S35492-35493 ***) Screw; wood, fathead, cross recessed MS51976-51977 Setscrew, hex, socket, half dog point M S35494-35495 Screw: wood, flat & round hd., slotted MS51981-51982 Setscrew, hex. socket, oval point Par 7-195 Page 7-59