General Specification - GotsToGo

1 JPL Spec ES504255 IGeneral SpecificationCODE IDENT NO. 23835 SPEC NO. ES504255, REV IISSUE DATE 2/9/99 SUPERSEDING ES504255 HDATED 6 JANUARY 1999 torque REQUIREMENTSMECHANICAL THREADED FASTENERS(SPACECRAFT STRUCTURE EQUIPMENT) General Specification FOR* Printed copies of this document may not be current and should not be used for officialpurposes. The current version is in the DMIE Information System at http://dmieJet Propulsion LaboratoryCalifornia Institute of TechnologyJPL Spec ES504255 IJPL Spec ES504255 IiTABLE OF National Form Stress , Screws and of Fasteners torque and Screw with Flush Head torque Fasteners Preloads for Bolts/Screws Installed Into Spec ES504255 torque Equipment and Nylon Screws and Coefficient Wrench Multiple Length and FOR Locking Spec ES504255 IiiiTABLE OF CONTENTS (cont'd)

2 , Bolts/Screws, and Nuts at 80 Nuts and Anchor Nuts at 125 , at 160 ksi, Into Inserts Assembled in6061-T6 , at 190 ksi, Installed Into InsertsAssembled in 6061-T6 Aluminum , at 160 ksi, Into Invar andHigher Shear Strength Aluminum , at 190 ksi, Into Invar andHigher Shear Strength Aluminum , at 160 ksi, assembled in Tapped , at 190 ksi, assembled in Tapped Prevailing and Minimum Breakaway Fasteners Assembly Engagement and Spec ES504255 This engineering Specification defines the standard torque to be applied tothreaded fasteners during spacecraft The amount of torque applied establishes the preload in the fastener and the jointclamp-up. Incorrect preload may result failure of the failure of a joint failure of the Torques. Nonstandard torque values not covered in this Specification shall becalled out on the controlling drawing, with any applicable procedures to be applied, as a drawing The following documents, of the issue as specified in the contractual instrument (oras specified for use within JPL), form a part of this Specification to the extent specified herein:SPECIFICATIONSJPLES516101 torque Requirements, Threaded Fasteners, ElectronicPackaging Equipment, General Specification forFederalGGG-W-686 Wrench, TorqueMilitaryMIL-S-7742 Screw Threads, National and Unified National, Preferred SizesMIL-S-8879 Screw Threads, Controlled Radius Root with Increased MinorDiameter, General Specification forMIL-DTL-18240 Fastener Element, Self-Locking, Threaded Fastener, 250?

3 F Nut, Self-Locking, 250 Deg F, 450 Deg F, and 800 Deg FNASCNAS618 Fastener-Recommended Shank, Hole and Head-to-Shank FilletRadius forJPL Spec ES504255 I4 STANDARDS JPLDS83 Screw, Internal Wrenching, 160 ksi and 190 ksiDS132 Screw, Pan Head, Hi- torque Recess, Full Thread, 160ksi CRESDS134 Screw, Countersunk Head, Hi- torque Recess, Full Thread, 160 ksi and 190 ksi, CRESDS136 Bolt, Close Tolerance 12-Point External Wrench, 160 ksi and 190 ksi, CRESQAI85-15-6-001 Calibration torque DevicesST10051 Screw, Cap, Socket Head Hexagon, 80 ksi, CRESST10060 Nut, Hexagon, Self-Locking, CRESST10072 Screw, Pan Head, Cross Recess, 80 ksi, CRESST10073 Screw, Pan Head, Hi- torque Recess, 160 ksi, CRESST10224 Rivnut, Blind, Flat Head, Closed End, Keyed, Aluminum AlloyST10225 Rivnut, Blind, Countersunk Head, Closed End, Keyed,Aluminum AlloyST11326 Insert, Non-Locking, Threaded, Miniature, Open EndST11294 Rivnut, Blind, Flat Head, Open End, Keyed, Aluminum Alloy 90273 Washer, Countersunk, CRES FederalFED-STD-H28 Screw Thread Standards for Federal Services Military MS21076 Nut, Self-Locking, Plate, Two Lug Floating, UNC andUNF2A CRESMS24693 Screw, Machine, Flat Countersunk Head, Gross RecessMS35649 Nut, Plain, Hexagon, Machine, UNC-2B, CRESMS35650 Nut, Plain, Hexagon, Machine, UNF-2B, CRESMS35691 Nut, Plain, Hexagon, UNF-2B, CRESJPL Spec ES504255 I5MS51957 Screw, Machine, Panhead, Cross Recess, UNC-2A, CRESMS51958 Screw, Machine, Panhead, Cross Recess, UNF-2A, CRESNASCNAS1216 Screw.

4 Pan Head Slotted Dovetail Recess, Full Threaded Self-Locking OptionalNAS1351 Screw, Cap, Socket Head Undrilled and Drilled, Plain and Self-Locking Alloy Steel, Corrosion-Resistant Steel and Heat-Resistant Steel, UNRF-3 ANAS1352 Screw, Cap, Socket Head Undrilled and Drilled, Plain and Self-Locking Alloy Steel, Corrosion-Resistant Steel and Heat-Resistant Steel, UNRC-3A and UNRC-2A NAS1348 Fasteners - Recommended Tensile Stress Areas for External ThreadedNAS1394 Insert, Threaded, Metal, Lightweight, CRESNAS1395 Insert, Threaded, Metal, Heavy Duty, CRESNAS1580 CBolt, Countersunk Head, CRES CommercialHi-Shear Corp. (CAGE 73197)BB414 Blind Nut Assembly, Blind ExpanderBB415 Blind Nut Assembly, ExpanderRexnord, Inc.

5 (CAGE 29372)KNB( )JInsert, Non-Locking, Lightweight, BlindKNCB( )JInsert, Non-Locking, Miniature, BlindKNC( )JInsert, Non-Locking, MiniatureKNHB( )JInsert, Non-Locking, Heavy Duty, BlindShur-Lok Corp. (CAGE 97393)SL6061 CInsert, Blind, Threaded Molded-in, CRESSL6096 CInsert, Threaded, Molded-in, CRESJPL Spec ES504255 I6 (Copies of specifications, standards, procedures, drawings, and publications requiredby suppliers in connection with specific procurement functions should be obtained from the procuringactivity or as directed by such activity.) Requirements. Conflicts arising between the requirements of this specificationand the requirements of any document referenced herein shall be referred to the procurement activity, ifany, or if not, to the cognizant engineer of the Mechanical Engineering Section (352) for Where possible, hole diameters and tolerances shall conform to Holes shall be drilled perpendicular to the surface within Holes shall be smooth and free from any drill chatter or scoring (Roundness).

6 Holes shall be round within the best shop practice. Holes may bereamed for shear and critical After the holes are machined, they shall be cleaned to remove all contaminantsbefore the bolts are Threads. There will be two different fastener thread series referenced in National Thread. The Unified National inch thread conforms to FED-STD-H28 Form Thread. The J form thread has the MIL-S-8879 thread form. Threads. The J form threads are preferred. The J form external thread shall notbe used with internal Unified National form, MIL-S-7742, without the specific approval of the Stress Area. Bolt root areas are used to calculate the preloads listed herein. (See ) , Screws and Nuts. The bolt, screw or nut shall not be reworked in any manner; thisincludes drilling, filing, cutting, using a tap or die, or any other mutilation, unless approved by thecognizant engineer, reidentified and inspected by Parts.

7 The listing of a part in the torque Tables does not imply the part isapproved for General use. See Section 352 Fastener Specialist for of Fasteners Used. Only as many fasteners as are anticipated to be installed andJPL Spec ES504255 I7tightened during a work shift shall be taken from protective stores. Fasteners not used shall be returnedto protective storage containers at the end of the Sockets and wrenches shall not have sharp edges or burrs that could damage thefastener plating or Application. torque shall be applied to the nut to the maximum extent possiblewhen a nut is present. Whenever clearance is a problem, torque may be applied to the bolt head, to thehigh side of the torque range specified in the torque torque . The torque applied at final assembly shall include the net effect of torque required to overcome kinetic friction between mating bearing faces andbetween mating threads, plus; torque required to overcome the self-locking feature (if any), plus; torque required to apply the desired axial load to a fastener installation torque shall be measured only in the tightening torque Values.

8 The torque values selected from Tables I through IX are based onthe maximum preload capability of the weaker member of the joint (either the internally threaded orexternally threaded part). Self-Locking Fasteners. The self-locking and breakaway torque of fasteners shall bemeasured as specified in The self-locking torque shall be added to the value listed in the applicabletable and the fastener installed to that torque Engagement. The nut, nutplate, insert, etc., shall not engage any incomplete threadsadjacent to the bolt or screw Identification. Any identification mark on the washer used under the nut shall beplaced opposite the face of the Features. Threaded fasteners should contain a self-locking feature in eitherthe external, or internally threaded part to prevent joint loosening. Self-locking bolts and screws shall bereadily identifiable by marking or discrete part Criteria.

9 The locking elements of self-locking screws and nuts are graduallydegraded with use (an average life of 5 to 10 installations). The prevailing (or running) torque of eachscrew shall be measured during installation, prior to type approval (TA) and flight acceptance (FA)testing and final assembly. The minimum breakaway torque requirements for certain fastenercombinations are listed in Table X. When a screw or nut fails to develop the minimum breakawaytorque, replace it with a new screw or nut. Length. Install fastener threads to extend through nuts, or nutplates to comply withthe thread minimum protrusion requirements shown in Table XII. Depth of fastener threads into tappedholes or free running inserts shall be one diameter minimum. Depth of fastener threads into lockinginserts shall be as above or a minimum of threads through the locking element, whichever is Spec ES504255 and Screw Length.

10 A bolt or screw one size longer or shorter than that specified on theengineering drawing may be substituted are only replaced by flight certified fasteners from flight are stock items, controlled or special order bolts and screws readily available innext length Adjustment. When a longer bolt or screw is substituted, additional washers may beadded to the ones specified on the engineering drawing subject to the following number of washers used on a fastener shall be limited to three: one washer underthe head and two under the nut, or two under the head and one under the washers shall be installed under bolt heads with the countersunk sidefacing the bolt Washers shall be used in accordance with the engineering drawing, applicableprocess bulletins and design standards, to reduce or eliminate threads in bearing, or to prevent dissimilarmetal contact.