"Settling down" is the term ESNA labora- FASTENERS tory people use to describe a relaxation phenomenon that occurs at room tem- perature under static conditions. During the first few hours after a nut and bolt FIRST LOOSEN are tightened on an arbor, the fastener system has lost some of its pre-stress. WITHOUT TURNING! The mechanical fits and finishes involved determine to a great extent how much initial clamping load will be lost. With precise, well-finished parts, this relaxa- tion may be limited to 2 or 3 per cent of pre-stress. With rough surfaces, loose thread tolerances and lack of squareness, Schematic of all-metal fastener testing histories shows how bolt tension is lost first in the static condition and then, more rapidly, after vibration begins. The nut turns at a critical tension level. INITIAL BEST AIRCRAFT -QUALITY FASTENERS POOREST COMMERCIAL - QUALITY FASTENERS NUT DOES NOT TURN CRITICAL F _J 0 w NUT ROTATES O FAILURE RANGE STATIC VIBRATION TESTING 13 Aircraft Technical Book Company http://www.ACTechbooks.com (800) 780-4115 (970) 887-2207 as much as 10 per cent of the original twisted during tightening. loading may be lost. When a retightened fastener system is This stress relaxation is analogous to subjected to a vibration test, loss of high-temperature creep. We suppose that clamping force continues, but at a rate it involves a gradual adjustment as local- much slower than occurred initially. The ized zones stressed beyond the yield point nut does not turn on the bolt while that transfer load to adjacent metal. Another is happening. Nevertheless, bolt tension mode of relaxation was observed by decreases as the vibration test progresses. Professor Wright® of the University of The mechanism of loosening in this phase Illinois in connection with torque-tension — before any relative thread turning oc- studies of bolting for structural steel. He curs — is not known accurately. It is found that part of the pre-stress loss that probably a combination of local yielding occurred within a few hours after tighten- and wear. The vibrations tend to ham- ing was accounted for by rotation of one mer down and wear away minute metal end of the bolt as it recovered from being projections on all bearing surfaces. For any given nut type plain or self-locking and a given level of vibration intensity, resistance to loosening is influenced in large measure by bolt tension at the start of the test. At the critical tension level, the nut begins to turn, then comes off very soon. HIGH INITIAL BOLT TENSION CRITICAL LEVEL AT WHICH NUT BEGINS TO ROTATE ON MODERATE INITIAL BOLT TENSION BOLT z 0 (7) z w _J 0 LOW INITIAL BOLT TENSION CO 0 VIBRATION TESTING 14 Aircraft Technical Book Company http://www.ACTechbooks.com (800) 780-4115 (970) 887-2207 NAS NAS 333 thru NAS 340 NAS 663 thru 668 100° Flush Head Bolt - Phillips Recess Flush Head Bolt, Titanium SPS Santo Ana, Calif. Only Hi-Torque and Phillips Recess SPS Santa Ana, Calif. NAS 428 Crown Hex Head Bolt NAS 673 thru 678 IIIIIIIIIII SPS Santa Ana, Calif. Hex Head Bolt, Titanium 11111111111 SPS Santa Ana, Calif. NAS 443 Internal Wrenching Nut NAS 679 (96) SPS Jenkintown, Pa. Lightweight Sheet Metal Locknut I o sal NAS 679C, 900°F (97) SPS Santa Ana, Calif. NAS 464 Hex Head Bolt 11111111111 16 0 SPS Santa Ana, Calif. NAS 680 and NAS 681 Nutt-Shel, Self-locking Plate Nut Two Lug NAS 501 SPS Santa. Ana, Calif. 11111111111 1::11 ) S/S Hex Head Bolt SPS Santa Ana, Calif. NAS 682 and NAS 683 Nuft-Shel Self-locking Plate Nut NAS 517 One Lug 11111111111 100° Flush Head Bolt SPS Santa Ana, Calif. I SPS Santa Ana, Calif. NAS 684 and NAS 685 NAS 560 Nutt-Shel Self-locking Plate Nut 11111111111 Screw - Hi Temp 100° Flush Head Corner 10 321 S/S, A286 or Inconel "X" as required SPS Santa Ana, Calif. SPS Santa Ana, Calif. NAS 686 4 NAS 561 Nutt-Shel Self-locking Plate Nut Spring Pin Floating - Two Lug S/S and Carbon Steel SPS Santa Ana, Calif. SPS Jenkintown, Pa. NAS 687 NAS 563 thru NAS 572 Nutt-Shel Self-locking Plate Nut 11111111A1() Hex Head Bolt Floating - One Lug SPS Santa Ana, Calif. SPS Santa Ana, Calif. NAS 583 thru NAS 590 NAS 696 100° Flush Head Hi-Torque Bolt Nutt-Shel Self-locking Plate Nut 95,000 psi Min. SS Miniature - One Lug SPS Santa Ana, Calif. SPS Santa Ana, Calif. NAS 607 NAS 697 Unbrako - Dowel Pin Nutt-Steel Self-locking Plate Nut I CD SPS Jenkintown, Pa. Miniature - Two Lug SPS Santa Ana, Calif. NAS 608 - NAS 609 Unbrako - Std. Socket Head Cap Screw NAS 698 SPS Jenkintown, Pa. Nutt-Steel Self-locking Plate Nut Miniature - Corner SPS Santa Ana, Calif. NAS 624 thru NAS 644 11111111 12 Point Bolt SPS Jenkintown, Pa. NAS 1003 thru NAS 1020 Hex Head Bolt 111 11111111 SPS Santa Ana, Calif. 11111n 410NAS 653 thru NAS 658 11111111111 Hex Head Bolt, Titanium SPS Santa Ana, Calif. NAS 1021 and NAS 1022 Flexloc Nut - Self-locking Std. Regular Height and Thin Nuts SPS Jenkintown, Pa. 16 Aircraft Technical Book Company http://www.ACTechbooks.com (800) 780-4115 (970) 887-2207 NAS continued NAS 1023 and NAS 10 24 NAS 110 1 Nutt-Shel Self-locking Plate Nut Flat Fillister Head Screw, Two Lug Torq-Set SPS Santa Ana, Calif. Alloy Steel and A286 SPS Santa Ana, Calif. NAS 1025 and NAS 1026 Nutt-Shel Self-locking Plate Nut NAS 110 2 One Lug 100° Flush Head Screw, SPS Santa Ana, Calif. Torq-Set Alloy Steel and A286 SPS Santa Ana, Calif. NAS 1027 and NAS 1028 Nutt-Shel Self-locking Plate N'.t Corner NAS 110 3 thru NAS 1120 SPS Santa Ana, Calif. Hex Head Bolt 9 o SPS Santa Ana, Calif. NAS 1031 Nutt-Shel Self-locking Plate Nut NAS 1121 thru 1128 Floating - Two Lug Flat Fillister Close Tolerance Bolt SPS Santa Ana, Calif. Torq-Set 111111\1 I Alloy Steel and A286 SPS Santa Ana, Calif. NAS 1032 Nutt-Shel Self-locking Plate Nut Floating - One Lug NAS 1131 thru 1138 SPS Santa Ana, Calif. Pan Head Bolt, Close Tolerance, Torq-Set Alloy Steel and A286 NAS 1033 SPS Santa Ana, Calif. Nutt-Shel Self-locking Plate Nut Floating - Right Angle SPS Santa Ana, Calif. NAS 1131 thru 1138 (Titanium) Pan Head Bolt, Close Tolerance, 1111111111 Torq-Set NAS 1067 10 SPS Santa Ana, Calif. Nutt-Shel Self-locking Plate Nut Miniature - Modified Base SPS Santa Ana, Calif. NAS 114 1 thru 1148 4 Brazier Head Bolt, Close Tolerance, 1111111111 Torq-Set NAS 1068 Alloy Steel and A286 Nutt-Shel Self-locking Plate Nut SPS Santa Ana, Calif. Floating Miniature - Two Lug SPS Santa Ana, Calif. NAS 115 1 thru 1158 100° Flush Head Bolt, NAS 1081 11111111111 Close Tolerance, Torq-Set Hex Socket Set Screw - Self-locking Alloy Steel and A286 11',111111111111111111 • SPS Jenkintown, Pa. SPS Santa Ana, Calif. NAS 1083 thru 1088 NAS 115 1 thru 1158 (Titanium) 100° Flush Head Bolt, Titanium 100° Flush Head Bolt, 0 Phillips and Hi-Torque 11111111111 Close Tolerance, Torq-Set SPS Santa Ana, Calif. SPS Santa Ana, Calif. NAS 1096 NAS 1161 thru 1168 Screw, Hex Head, Recessed 100° Flush Head Bolt, Full Thread G1111111 Self-locking, Torq-Set SPS Santa Ana, Calif. SPS Santa Ana, Calif. NAS 1100 NAS 1171 thru 1178 Pan Head Bolt, Torq-Set Recess Pan Head Bolt, Self-locking, Alloy Steel and A286 e Torq-Set SPS Santa Ana, Calif. SPS Santa Ana, Calif. 17 Aircraft Technical Book Company http://www.ACTechbooks.com (800) 780-4115 (970) 887-2207 AN737 CLAMPS AN737RM Radial-Machine Screw Type AN737 Hose Clamps are for use on fuel, Clamp band is 5/8" wide and .020" oil and coolant lines. Installation can thick for all sizes. The band is welded be made while hose is in place; clamps to the nut by certified spot-welding may be tightened repeatedly while in ser- methods. This unit, when assembled to vice. No lock wire needed. All parts of the bridge and its flexible bridge exten- these clamps are made of stainless steel der, provides a clamp which combines except the thumbscrews which are cad- superior strength with uniform clamping mium plated carbon steel. All clamps action. Order by AN part number, per meet current MIL and AN specifications. table below. Example: AN737RM22 is a single size, radial-machine screw type clamp having a minimum I.D. of 7/16". AN737TW Tangential-Worm Screw Type The one-piece curved housing is spot- welded to the recessed band on certified equipment to form an integral unit. Con- tour serrations give greater band strength and are a perfect mate for the buttress thread of the screw for smooth clamping action. Order by AN part number per table below. Example: AN737TW22 is a single size, tangential-worm screw type clamp having a minimum I.D. of 7/16". Clamps are easily installed or removed with hose In place ORDERING TABLE AN737 Hose Clamps MIN. I.D. MAX. I.D. FOR USE WITH HOSE I.D. DASH OF CLAMP OF CLAMP NON SELF- SELF- NO. STRUT VALVES (INCHES) (INCHES) SEALING SEALING — 22 2/14 "A e 1/4 — 24 '/2 3/4 Vie — 26 'A t "A. % iiii, AN812-1 — 30 ' Vie 1/2 High Pressure Valve designed for shock ' Yie 1 Vie struts and accumulators to permit inflation — 34 % and gauging. Less AN809- 1 core and — 38 ' Vie 1 Yls 3/4 AN813-1B valve cap.