1、17 JUNE 1964 SUPERSEDING 28 NOVEMBER 1950 MIL-N-3336 MILITARY SPECIFICATION NUTS, SELF-LOCKING, CLIP-IN TYPE, INSTRUMENT MOUNTING Thz specification has been approved by the Department of Defense and .is man- dam fm use by the Departments of the Amy, the Navy, and the Air Force. 1. SCOPE 1.1 Scope. T
2、his specification covers certain design and all performance Requirements for the procurement of clip-in, self-locking nuts for installing flange-mounted instru- ments. 1.2 Classification. The nuts shall be fur- ished in accordance with the MS33737 part numbers specified (see 6.2). 2. APPLICABLE DOCU
3、MENTS 2.1 The following documents, of the issue in effect on date of invitation for bids or re- quest for proposal, form a part of this speci- fication to the extent specified herein : SPECIFICATIONS FEDERAL, QQ-P-416 -Plating, Cadmium (Electrodeposited) QQ-2-325 -Zinc Coating, Electro- deposited, R
4、equire- ments for MILITARY MIL-P-116 -Preservation, Methods of MIGH-3982 -Hardware (Fasteners and Related Items), Packaging and Psck- ing for Shipment and Storage of MIGE-5272 -Environmental Testing, Aeronautical and As- sociated Equipment, General Specification for MIGC-5541 -Chemical Films for Alu
5、minum and Alum- inum Alloys MIL-A-8625 -Anodic Coatings, for Aluminum and Alum- inum Alloys MIL-D-70327-Drawings, Engineering and Associated Lists STANDARDS MILITARY MIGSTD-105-Sampling Procedures and Tables for In- spection by Attri- butes and Standards, Order of Precedence for the Selection of AIS
6、33737 -Nut, Instrument Mounting, Self Lock- ing, Clip-in Type MIGSTD-143-S p eci f i ca t i on s AIR FORCE-NAVY AERONAUTICAL AN 515-Screw, Machine, Round Head, Coarse Thread PUBLICATION NATIONAL BUREAU OF STANDARDS Handbook HBS,-Screw-Thread Stan- Part I dards for Federal Services Licensed by Inform
7、ation Handling ServicesProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-N-333bA 53 3979706 00963LLt 4 m- MILN-3336A (Copies of specifications, standards, drawings, and publications required by suppliers in connection with specific procurement func
8、tions should be obtained from the procuring activity or as directed by the contracting officer.) 3. REQUIREMENTS 3.1 Qualification. The spring nut furnished under this specification shall be a product which has been subjected to and which has passed the qualification tests specified herein, and whic
9、h has been listed on or approved for listing on the applicable Qualified Products List. 3.2 Data. Unless otherwise specified in the contract or order, no data (other than reports and drawings accompanying qualifi- cation samples) are required by this specifi- cation or any of the documents reference
10、d in section 2 herein (see 6.2). 3.3 Selection of Government documents. Specifications and standards for necessary commodities and services not specified herein shall be selected in accordance with MIL- 3.4 Materials. Materials shall conform to applicable specifications and shall be as speci- fied h
11、erein. Materials for which there are no applicable specifications, or which are not specifically described herein, shall be of the best quality, of the lightest practicable weight and suitable for the purposes in- tended. Each nut shall be made entirely of nonmagnetic materials which are not nutri-
12、ents for fungi. 3.4.1 Metals. Metals shall be corrosion re- sistant, or shall be suitably protected as specified herein to resist corrosion due to fuels, salt spray or atmospheric conditions to which the instrument may be subject when in storage or during normal service life. 3.5 Design. The outline
13、 and dimensions of the instrument mounting nuts shall conform to MS33737. The nut shall consist of the nut proper and a holding device or cage to main- tain the nut in position while inserting and tightening the screw. The mounting nut as- sembly sba4.&, 4 o desiaed that it may be 2 - - - STD-143. P
14、- -1- - 2, set in place in holes of specified diameter, without the use of special tools and shall hold in place against insertion of the screw. 3.5.1 Screw threads, Each nut shall be de- signed to be used with screws having threads conforming to Handbook H28, part I, class 2A for the size and pitch
15、 specified in MS33737. Each nut shall be so designed that an unlimited length of screw can be threaded completely through it. 3.5.2 Panel thickness. Each nut shall be designed to be used as shown on figure 1 in a hole in instrument panels of the thicknesses specified in MS33737. 3.5.3 Installation a
16、nd removal. Each nut shall be so designed that it can be easily installed in and removed from a hole in an instrument flange or instrument panel con- forming to figure 1 without the use of any tool. 3.6 Torque. 3.6.1 Prevailing torque. The prevailing torque for the first removal shall be : Screw thr
17、eads First removal prevailing size and pitch torque, inch-pounds 4-40 0.375 2 0.125 6-32 0.5 2 .375 8-32 0.75 -1- ,375 10-24 1.00 -t- .5 The prevailing torque for the fifteenth re- moval shall be at least : Screw threads Fifteenth removal. minimum size und pitch prevatltng torque, anch-pounds 4-40 0
18、.1876 6-32 .25 8-32 ,375 10-24 .5 3.6.2 Position torque. The nut shall with- stand the following torque, without turning, when installed in a 5052 half-hard, aluminum alloy panel. This torque shall be measured without a screw installed in the nut. Screw threads Position tor ue, size and pitch inch-p
19、ods 4-40 1 6-32 1.5 8-32 2 10-24 3 -3.6.3 Maximum torque. The nut when properly installed in a panel shall withstand, _ - - - / Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- MIL-N-333bA 53 9999906 0096935 b IMIG-N-3336A without turning or being da
20、maged, the fol- lowing torque applied to the screw in the tightening direction : Screw threads Maximum torque, size ana pitch inch-pounds 4-40 6 6-32 8 8-32 12 10-24 16 3.7 Tension strength. The nut shall with- stand the following tension load, applied to the screw head and parallel to the axis of t
21、he screw, when the nut and screw are prop- erly installed in a panel. Screw threads Maximum tension size and pitch strength, pounds 4-40 100 6-32 150 8-32 200 10-24 300 3.8 Weight. The weight of the nuts shall be expressed as the weight of 1,000 nuts of each MS33737 part number. The weight shall not
22、 exceed that specified on MS33737 for each part number. 3.9 Vibration. The nut shall withstand vibration for 20 hours at frequencies varied slowly between 500 and 3,000 cycles per sec- ond and at an amplitude of 0.018 to 0.020 inch, without loosening of the screw or other evidence of nut failure. 3.
23、10 Finish. Copper, brass, or bronze parts which may be in contact with aluminum shall be cadmium plated in accordance with QQ- P-416, type I, class 2 or zinc plated in ac- cordance with QQ-2-325. Aluminum alloy parts or assemblies shall be anodized in ac- cordance with MIL-A-8625. Aluminum al- loys
24、which do not anodize satisfactorily shall be coated with chemical film in accordance with MIL-(3-5541. The finishes shall not cor- rode when the nuts are subjected to the salt spray test. 3.11 Interchangeability. All nuts having the same MS part number shall be completely interchangeable with each o
25、ther with respect to installation and performance regardless of differences in manufacturers and aircraft in which installed. Changes in manufactur- ers part numbers shall be governed by the v -7 drawing number requirements of MIL-D- 70327. 3.12 Identification. The MS33737 part number of the nut and
26、 the manufacturers trademark or other means of identifying the manufacturer shall be stamped on each nut. 3.13 Workmanship. All details of work- manship shall be such as to assure compli- ance with this specification. The nuts shall be free from tool marks, burrs, flaws, and all other defects which
27、may affect their servicea- bility. 4. QUALITY ASSURANCE PROVISIONS 4.1 Responsibility for inspection. Unless otherwise specified in the contract or pur- chase order, the supplier is responsible for the performance of all inspection require- ments as specified herein. Except as other- wise specified,
28、 the supplier may utilize his own facilities w any wmmereial Iaboratory acceptable to the Government. The Govern- ment reserves the right to perform any of the inspections set forth in the specification where such inspections are deemed necessary to assure supplies and services conform to prescribed
29、 requirements. 4.2 Classification of tests. The inspection and testing of the clip-in nuts shall be classi- fied as : (a) Qualification tests (4.3) (b) Quality conformance tests (4.4) 4.3 Qualification tests. The qualification tests of the clip-in nuts shall consist of all of the examinations and te
30、sts specified under 4.6 and 4.7. 4.3.1 Quulifiatzon samples. Qualification test samples shall consist of 100 nuts, of each MS33737 part number on which qualification is desired. Samples shall be marked and shipped as directed by the activity responsi- ble for qualification in the letter of authori-
31、zation therefrom (see 6.4) , 4A Quality conformance testa. 4.4.1 Sampling. Samples shall be selected in accordance with inspection level II of MIL-STD-105 with an acceptable quality Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-AIIGN-3336A level of
32、 1.5. Samples for preparation for de- livery shall be selected at random and the containers shall be fully prepared for de- livery, except that the container need not be sealed. 4.4.2 Tests. The quality conformance tests shall consist of the following tests conducted in the order listed, on each nut
33、 selected as specified in 4.4.1 : (a) Examination of product (4.6.1) . (b) Prevailing torque I (4.7.1) (c) Position torque (4.7.2) ,. (d) Maximum torque (4.7.3) (e) Tension strength (4.7.4) 4.4.2.1 Samples for preparation for deliv- ery, selected in accordance with 4.4.1, shall be examined in accord
34、ance with 4.6.2. 4.4.3 Rejection and retest. The instruc- tions on reworking, refurbishing or resub- mitting rejected items shall be as specified in the general provisions of the contract or order. 4.5 Test conditions. 4.5.1 Ambient temperatwe. Unless other- wise specified, all tests of this specifi
35、cation shall be performed at room temperature. If a nut fails a test for which no ambient tem- perature other than room temperature is specified, and in the opinion of the inspector the nut might pass the test in an ambient temperature of 70“ F, the test shall be reper- formed with the nut in the am
36、bient tempera- ture of 70“ &lo F. 4.5.2 Test piute. Whenever a test plate is specified, it shall be fabricated from 6062 half-hard, aluminum alloy of the thickness specified in MS33737. Each nutphall be in- stalled in a hole in the test plate which shall conform to figure 1 for the screw thread size
37、 and pitch specified in MS33737. The holes shall be far enough apart that no two nuts or washers (see 4.7.5) can touch each other or any position of rotation of the nuts. 4.5.3 Screws. All screws used in the tests shall be brass conforming to AN616 and of the smallest length which will engage all of
38、 the threads of the nut. 4 7 MIL-N-333bA 53 4779706 00769Lb 4 -. - - - 4.6 Examinations. 4.6.1 Examination of product. The nut shall be examined, measured, weighed, etc., as necessary to determine conformance to all requirements of this specification for which there are no specific tests. 4.6.2 Prep
39、amtion for deliver&. The pres- ervation, packaging, packing, and marking shall be examined to determine conformance to section 6. 4.7 Test methods. . 4.7.1 Prevailing torque. The nut shall be tested for prevailing torque by screwing a screw into and out of the nut without axial load on the screw oth
40、er than that required to keep the screwdriver in the screw slot. Each installation and removal of the screw shall consist of four turns of the screw after it has first made contact with the threads of the nut. The test shall be run slowly enough to obtain a dependable measure of the torque. The torq
41、ue shall be measured while the screw is being removed during the fist and fifteenth removals and shall conform to 3.6.1. 4.7.2 Position torque. The nut shall be in- stalled in a test plate and the torque required to turn the nut in the hole, without any screw installed in the nut or any linear force
42、 applied to the nut, shall be measured and shall conform to 3.6.2. 4.7.3 Maximum torque. The nut shall be installed in a test plate and a screw shall be installed in the nut and tightened to the torque specified in 3.6.3, &IO percent. The nut shall not rotate or be damaged in any way by this test. 4
43、.7.4 Tension strength. The nut shall be installed in a test plate, and a screw passed through a suitable yoke or brass stud having threads conforming to 3.5.1, and a collar simulating a screw head shall be screwed into the nut and tightened to the torque specified in 3.6.3, -10 percent. The load spe
44、cified in 3.7, & 10 percent, shall then be applied axially to the screw or stud. The screw orstud shall not come out of the nut, nor shall the nut I_-* Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-F1GR.E 1. Flange or panel hole 7 5 Provided by IHS
45、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-N-333bA 53 W MIL-N-3336A fail or be damaged in any way as a result of this test. 4.7.5 Vibration. The nut shall be installed in a test plate and a flat circular washer having a diameter of 1 k0.05 inch and a hole
46、of a size appropriate for the screw shall be clamped to the test plate by a screw installed in the nut. The washer shall be of 5052 half-hard aluminum alloy of the follow- ing thickness : Screw threads Vlbrqtion test size and pitch washer thzckness (inch) 4-40 0.125 6-32 8-82 10-24 .1875 .26 ,375 Th
47、e screws shall be tightened to the torque specified in 3.6.3 and the test plate shall be mounted in a vertical plane on a vibration stand and shall be vibrated as specified in 3.9. Neither the nut, the screw, nor the washer shall turn, shift, or loosen as a re- sult of this test. 4.7.6 Salt spray. T
48、he nuts, installed in a test plate with screws installed in them, shall withstand salt spray tests in accordance with Procedure II of MIL-E-5272, except that the time period shall be 192 hours without indi- cations of corrosion which cannot be wiped off with a damp cloth. 5. PREPARATION FOR DELIVERY
49、 5.1 Preservation. Preservation shall be in accordance with Method IA of MIL-P-116, without the use of contact preservative. 5.2 Packaging, packing, and marking. Packaging and packing shall be level A, B, or C, as specified (see 6.2), and marking shall be in accordance with MIL-H-3982. Pack- aged quantities shall be as specified. 6. NOTES 6.1 Intended use. The nuts are intended for use in installing flange-mounted instru- ments on aircraft instru
