IFI-524-1996.pdf

1. Scope. INDUSTRIAL FASTENERS INSTITUTE 1717 East 9th St., Suite 11 05 Cleveland, Ohio 441 14 USA 1.1 This Standard establishes a conformance test procedure for the performance of metric Nonmetallic Resistant Element Type Prevailing Torque Screws (hereinafter called REPT screw), in nominal thread diameters M1.6 thru M36. The prevailing torque values given in this Standard are conformance requirements of test conditions described in the performance test procedure (4.1). If the conditions of the actual service application differ from those of 4.1 (e.g., internally threaded hole in a different material, length of thread engagement, class of internal thread tolerance, speed of driving, different plating or coating on screw or mating part), the prevailing torque values may differ. Such values can only be determined through testing the REPT screw in its specific application. This Standard is not concerned with dimensional features such as head styles, or with other mechanical or performance capabilities such as strength properties, corrosion resistance, sealing, suitability for use in high or low temperatures, and/ or consistency of torque-to-tension relationships during assembly. Such features and properties are covered in other standards and specifications and must be referenced when specifying a REPT screw to assure that all of the service conditions of the particular engineering application are properly met. (Note: The application of some nonmetallic elements requires heating of an isolated area in the screw thread to approximately 6OOpF which may have an adverse effect on the mechanical properties of some products.) 1.2 While the requirements of this Standard apply to REPT screws, it is not the intent to preclude alternate types of screws which totally satisfy the requirements of this Standard. 1.3 Definitions. 1.3.1 A prevailing-torque REPTscrew is an externally threaded fastener which is frictionally resistant to rotation due to a self-contained prevailing-torque feature, and not because of a compressive load developed against the under head bearing surface of the screw or a tensile load developed in the shank of the screw. 1.3.2 REPT screws are metallic screws to which have been added a nonmetallic insert or fused nonmetallic substance in their threaded length. The design of the prevailing-torque feature shall be in accordance with the practice of the manufacturer. Depending upon the amount of friction present because of surface finish and lubricants, the dimensional characteristics of the nonmetallic element may vary to achieve the performance requirements stated in Table 1. 1.3.3 For purposes of this Standard, “lot“ means a quantity of fasteners of one part number fabricated by the same production process from the same coil or heat number of metal as provided by the fastener manufacturer and submitted for inspection and testing at one time. 2.0 Property Classes. 2.1 Property Classes. This Standard covers only steel REPT screws produced to meet the mechanical strength requirements of one of four basic property classes, 8.8,9.8,10.9 and 12.9 as specified in ASTM F568. The standard sizes of REPT screws for each of the four property classes are given in Table 1. 3.0 Requirements. 3.1 Finish. REPT screws shall be furnished plain or with a protective coating as specified by the purchaser. If tolerancing differs, see “Scope“ paragraph 2. At the option of the manufacturer, screws may be provided with a supplementary lubricant. I lFl-524 I FI STANDARD I TEST PROCEDURE FOR THE PERFORMANCE Revised: October 1996 OF METRIC NONMETALLIC RESISTANT ELEMENT Industrial Fasteners PREVAILING-TORQUE SCREWS titute of Cleveland, OH All standards and specifications are advisory only. Their use by anyone is entirely voluntary. Reliance thereon for any purpose by anyone is at the sole risk of that person or the user of the product, and the IF1 is not responsible for any loss, claim, or damage arising therefrom. In formulating and approving standards and specifications, the IF1 has not investigated and will not investigate patents which may apply to the subject matter. Prospective users of the standards and specifications are responsible for advising themselves of and protecting themselves against any patent infringement liability which may arise out of such use. O INDUSTRIAL FASTENERS INSTITUTE 1996 Copyright Industrial Fastener Institute Provided by IHS under license with IFILicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 06/12/2007 02:48:22 MDTNo reproduction or networking permitted without license from IHS -,-,- INDUSTRIAL FASTENERS INSTITUTE 1717 East 9th St., Suite 11 05 Cleveland, Ohio 441 14 USA Clamp Load (1) Nom kN Screw Size and Thread Pitch Property Class of Screw 8.8 9.8 10.9 12.9 M1.6 x 0.35 _ 0.6 - 0.9 M2 x 0.4 -_ 1 .o -_- 1.5 M2.5 x 0.45 -_ 1.6 _- 2.5 M3 x 0.5 - 2.4 _- 3.7 M3.5 x 0.6 _ 3.3 _-_ 4.9 M4 x 0.7 _-_ 4.3 _ 6.4 M5 x 0.8 _-_ 6.9 8.8 10 M6 x 1 _-_ 9.8 12 15 M8 x 1.25 _ 18 23 27 M10 x 1.5 - 28 36 42 M12 x 1.75 - 41 52 61 M14 x 2 _ 56 72 84 M16 x 2 -_- 76 98 110 M20 X 2.5 110 - 150 180 M24 x 3 160 _-_ 220 260 M30 x 3.5 250 - 350 41 O M36 x 4 370 _- 51 O 590 Table 1 - Prevailing Torques for Nonmetallic Resistant Element Screws First Removal Prevailing Torque Prevailing Torque max min Nam N .m 0.10 0.01 0.20 0.02 0.40 0.05 0.60 0.14 0.90 0.22 1.2 0.26 2.3 0.36 3.0 0.45 10 0.90 14 1.8 21 2.6 30 3.6 40 5.0 60 8 .O 90 13 120 19 150 28 Fifth Removal Prevailing Torque - I 0.004 0.03 0.01 1 0.23 0.30 I 0.58 7 1 5.5 8.5 13 18 l.2 Threads. l.2.1 Thread Tolerances. Threads of REPT screws hall be tolerance class 6g as specified in ASME 11.13M, except that the portion of the threaded mgth containing the nonmetallic element need not onform. If tolerancing differs, see “Scope“ paragraph 1.2.2 Thread Start. REPT screws, except those :overed in 3.3.2, shall assemble a minimum of one full Jrn by the fingers into any mating internally threaded :omponent that has threads acceptable to Gaging jystem 21 of ASME B1.3M. 1 . 3 Performance 3.3.1 The prevailing torque of REPT screws occurring during any installation or removal shall not exceed the maximum prevailing torque specified in Table 1 when tested as specified in 4.1. In addition, the highest prevailing torques developed by REPT screws during first and fifth removal shall not be less than the minimum first and fifth removal torques, respectively, specified in Table 1 when tested in accordance with 4.1. In addition, the lowest prevailing torque developed by REPT screws during the fifth removal shall not be zero, when tested in accordance with 4.1. 3.3.2 REPT screws which are too short or which have thread lengths too short to permit testing in accordance with 4.1 shall have their prevailing-torque requirements and test procedure established by agreement between the purchaser and manufacturer. lF1-524 Issued: 1982 Revised: October 1996 TEST PROCEDURE FOR THE PERFORMANCE OF METRIC NONMETALLIC RESISTANT ELEMENT ished and issued by Industrial Fasteners PREVAILING-TORQUE SCREWS tute of Cleveland, OH All standards and specifications are advisory only. Their use by anyone is entirely voluntary. Reliance thereon for any purpose by anyone is at the sole risk of that person or the user of the product, and the IF1 is not responsible for any loss, claim, or damage arising therefrom. In formulating and approving standards and specifications, the I F 1 has not investigated and will not investigate patents which may apply to the subject matter. Prospective users of the standards and specifications are responsible for advising themselves of and protecting themselves against any patent infringement liability which may arise out of such use. Q INDUSTRIAL FASTENERS INSTITUTE 1996 Copyright Industrial Fastener Institute Provided by IHS under license with IFILicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 06/12/2007 02:48:22 MDTNo reproduction or networking permitted without license from IHS -,-,- 4748550 0001058 8TO 'ublished and issued by 1 he Industrial Fasteners OF METRIC NONMETALLIC RESISTANT ELEMENT PREVAILING-TORQUE SCREWS INDUSTRIAL FASTENERS INSTITUTE Page30f Issued: 1982 1717 East 9th St., Suite 1105 Cleveland, Ohio 44114 USA nstitute of Cleveland, OH 3.4 When REPT screws are altered in any manner by any source following shipment by the manuacturer to a purchaser, the screw manufacturer shall not be held responsible for failures of the screws to meet dimensional or performance requirements traceable to the alteration. Revised: October 1996 4.0 Performance Test. 4.1 Test Procedure. The sample REPT screw shall be assembled with a test washer (4.1.6) and a test nut (4.1.3) in a load measuring device (4.1 .l) with the test washer located adjacent to the component to be turned. During the complete performance of the test, either the REPT screw or the test nut shall be turned. When the REPT screw is turned, the restraining mechanism shall be such that it imparts no radial distortion to the test nut. The REPT screw or test nut shall be advanced until its bearing surface is seated against the test washer. The total thickness of spacer material in the test assembly shall be selected so that at seating, the mid-length of the nonmetallic element of the screw shall coincide as closely as practical with the mid-thickness of the test nut, and a minimum length of REPT screw equivalent to two thread pitches shall project through the top of the test nut. During this first installation, the highest prevailing torque (first on torque) occurring while the REPT screw or test nut is in motion and prior to development of any axial load shall be measured and recorded. Tightening shall be continued until an axial tensile clamp load equal to the load as specified in Table 1 for the applicable screw size and property class is developed. The axial tensile clamp load in the REPT screw shall be reduced to zero by backing the turned member off until the test washer is free to move by the fingers.Following a pause '(it is generally necessary to change the wrench to one of a lower torque capacity), removal shall be continued and the highest torque (first removal torque) occurring while the REPT screw or test nut is being backed off throughout the next 360 deg of rotation shall be measured and recorded. The REPT screw and test nut shall be disassembled and then reassembled and disassembled four more times. On each reassembly the REPT screw shall be assembled with the test nut until the turned element is seated against the test washer, but no tensile load shall be induced in the REPT screw. During the fifth removal, the highest torque (fifth removal torque) occurring while the REPT screw or test nut is being backed off throughout the first 360 deg of rotation shall be measured and recorded. At no time during this 360 deg of rotation shall the torque be zero. At no time during the four additional installations and removals should the prevailing torque exceed the maximum prevailing torque as specified in Table 1. (Note: The intent of this preceding requirement is to demonstrate that galling between the sample REPT screw and test nut has not occurred. With certain designs of REPT screws there may be an increase in the prevailing torque during the five assembly cycles and in rare instances the specified maximum prevailing torque may be exceeded. In such instances the manufacturer, when requested, shall give evidence that galling was not a contributing factor.) Sufficient time shall elapse between torquing cycles to prevent overheating of the test assembly. Speed of driving shall not exceed 30 RPM. 4.1.1 Tensile Load Measuring Device. The tensile load measuring device shall be an instrument capable of measuring the actual tension induced in the REPT screw as it is being tightened. The device shall be accurate within plus or minus 5 percent of the tensile clamp load to be induced. Diameter of the REPT screw clearance hole in the backing plate shall be the REPT screw nominal size plus 0.4 mm for screw sizes M5 and smaller, plus 0.8 mm for sizes M6 to M24 incl., and plus 1.6 mm for sizes M30 and M36. I lFl-524 IF1 STANDARD I TEST PROCEDURE FOR THE PERFORMANCE Copyright Industrial Fastener Institute Provided by IHS under license with IFILicensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 06/12/2007 02:48:22 MDTNo reproduction or networking permitted without license from IHS -,-,- 9748550 OOOL059 737 INDUSTRIAL FASTENERS INSTITUTE 1717 East 9th St., Suite 1105 Cleveland, Ohio 441 14 USA 4.1.2 Torque wrenches shall be accurate within plus or minus 2 percent of the maximum of the specified torque range of the wrench. 4.1.3 Test Nut. The test nut shall conform to dimensions given in Table 2. Alternately, a test block may be used as long as its thickness and countersink comply with Table 2. Nuts shall be made of carbon steel, and shall have proof load strengths equal to or greater than the minimum specified ultimate strength of the screw being tested. 4.1.4 Thread Tolerance. All test nuts shall be Class 6H when testing screws with Class 6g or Class 4gGg.Test nuts shall be free of rust and dirt and shall have a plain finish with light oil coating. The screw shall be assembled into the countersunk side of the nut. Alternate testing using a gage block shall be used only by agreement of purchaser and supplier. Gage blocks must meet the same thread tolerance and physical requirements of test nuts. 4.1.5 Usage. A new test nut shall be used for testing each screw. Prior to the usage of a test nut, its threads shall be gaged and shall be acceptable to the requirements of Gaging System 21 of ASME B1.3M. Alternate testing with gage block shall require gaging prior to usage and gaging after each screw test to the requirements of Gaging System 21 of ASME B1.3M. 4.1.6 Test Washer. Washers shall be steel with dimensions, hardness and finish at option of testing agency, 5.0 Inspection. 5.1 Inspection Procedure. REPT screws shall be inspected to determine conformance with the requirements of this Standard. Unless otherwise specified, from each lot of REPT screws the following number of tests shall be conducted to determine the acceptability to each of the requirements: Lot Size I No.ofTests to 50 51 to500 501 to 35,000 over 35,000 Alternate inspection procedures may be specified by the purchaser on the purchase order or engineering drawing. lFl-524 Issued: 1982 Revised: October 1996 STANDARD 'ublished and issued by :he Industrial Fasteners PREVAILING-TORQUE SCREWS -i nstitute of Cleveland. OH TEST PROCEDURE FOR THE PERFORMANCE OF METRIC NONMETALLIC RESISTANT ELEMENT All standards and specifications are advisory only. Their use by anyone is entirely voluntary. Reliance thereon for any purpose by anyone is at the sole risk of that person or