10 major changes in the latest version of ISO nut

There are 10 major changes in the new ISO nut technical standard ISO 898

the third edition of ISO, from the formulation of the discussion draft iso/cd in 2008 to the submission of the draft in January 2010, which was not adopted in June 2010, and then again in December 2011. It was voted on by letter on February 15, 2012. After four years, it was finally published on March 15. So, what is the difference between the third edition of ISO and the second edition in 1992? 1、 The scope changes. The original ISO is the nominal diameter of thread D ≤ 39mm, now it is M5 ≤ D ≤ M39, and it also includes m8x1 ≤ D ≤ m39x3 fine thread nuts. The original nominal height ≥ 0.5d, and the current minimum nut height m ≥ 0.45d. Change the original inapplicable temperature above +300 ℃ to +150 ℃

second, the original nut grade 4 is deleted, and the grade 5 nut is matched with the bolt below grade 5.8

III. the requirements for carbon in steel composition of grade 5 and 6 nuts have been increased from 0.50% to 0.58%. It is clearly pointed out that the chemical composition of materials is only smelting analysis, and in case of dispute, product analysis will be the arbitration. This modification improves the requirements of nut material

IV. dilute the requirements of thin nuts on the mark to ensure load performance, and clearly put forward that such nuts only play the role of stopping and clamping, and cannot be designed to carry anti tripping. And how to use it is clearly expounded. That is, tighten the thin nut on the assembly workpiece first, and then tighten the ordinary nut or thick nut behind the thin nut

v. the new version points out that the basic tolerance of nuts with tolerance grade 6h is greater than zero, which will reduce the tripping strength of threads (such as hot-dip galvanized nuts: 6az, 6AX). The nut guarantees a minimum tripping strength of 98% of the load. Thus, the expression "reduction of thread strength" in Table 1 is replaced to remind the influence of expanding tapping size of hot-dip galvanized nuts

VI. compared with the original standard, the scope of forced quenching and tempering coarse or fine thread nuts is clearly specified, and coarse thread nuts with performance levels of 05, 8 [D ＞ M16 ordinary nuts], 10 and 12 should be quenched and tempered. Fine thread nuts of property grades 05, 6 (D ＞ M16), 8[ordinary nuts (type 1)], 10 and 12 shall be quenched and tempered. It is also suggested that the longitudinal section should be tested to ensure that 90% martensite structure exists before tempering. Whether other grades are quenched and tempered shall be determined by the manufacturer

VII. The requirements of guaranteed load are simplified, the cross-sectional area of thread stress and guaranteed stress matters are removed, and the guaranteed load requirements of type 1 and type 2 nuts in Grade 8 are combined on coarse thread, which improves the requirements of guaranteed load of type 2 nuts, the same as that of type 1 nuts; It also improves the guaranteed load requirements of type 1 nuts at level 12, which is the same as that of type 2 nuts. On fine thread, the guaranteed load requirements of type 1 and type 2 nuts in Grade 8 are combined, and the guaranteed load requirements of type 2 nuts are improved, which is the same as that of type 1 nuts; The guaranteed load requirements of type 1 and type 2 nuts with grade 10 nuts below m16x1.5 are combined, which are the same as type 1 nuts, as shown in the table below

guaranteed load value of coarse nut

thread D pitch P guaranteed load a, N performance grade m50.85 4007 1008 2509 50012 14013 00014 80016 300m617 64010 00011 70013 50017 20018 40020 90023 100m7111 00014 50016 80019 40024 70026 40030 10033 200m81.2513 90018 30021 60024 90031 80034 40038 10042 500m101.522 00029 00034 20039 40050 50054 50060 30067 300m121.7532 00042 20051 40059 00074 20080 10088 500m14243 70057 50070 20080 500101 200109 300120 800136 900m16259 70078 500 95 800109 900138 200149 200164 900186 800M182.573 00096 000121 000138 200176 600176 600203 500230 400M202.593 100122 500154 400176 400225 400225 400259 700294 000M222.5115 100151 500190 900218 200278 800278 800321 200363 600M243134 100176 500222 400254 200324 800324 800374 200423 600M273174 400229 500289 200330 500422 300422 300486 500550 800M303.5213 200280 500353 400403 900516 100516 100594 700 673 200m333.5263 700347 000437 200499 700638 500638 500735 600832 800m364310 500408 500514 700588 200751 600751 600866 000980 400m394370 900488 000614 900702 700897 900897 9001 035 0001171 000a for the use of thin nuts, it should be considered that the sliding buckle load should be lower than the guaranteed load of nuts with full bearing capacity

guaranteed load value of fine thread nut:

thread D × P guaranteed load a, n performance grade M8 × 114 90019 60027 00030 20037 40043 10047 000M10 × 1.2523 30030 60044 20047 10057 40067 30073 400M10 × 124 50032 20044 50049 70061 60071 00077 400M12 × 1.533 50044 00060 80068 70084 10097 800105 700M12 × 1.2535 00046 00063 50071 80088 000102 200110 500M14 × 1.547 50062 50086 30097 500119 400138 8 Hao Jiping thinks 00150 000m16 × 1.563 50083 500115 200130 300159 500185 400200 400M18 × 277 500102 000146 900177 500210 100220 300-M18 × 1.581 700107 500154 800187 000221 500232 200-M20 × 298 000129 000185 800224 500265 700278 600-M20 × 1.5103 400136 000195 800236 600280 200293 800-M22 × 2120 800159 000229 000276 700327 500343 400-M22 × 1.5126 500166 500239 800289 700343 000359 600-M24 × 2145 900192 000276 500334 100395 500414 700-M27 × 2188 500248 000351 100431 500510 900535 700-M30 × 2236 000310 50 for coherent technical parameters 0447 100540 300639 600670 700-m33 × 2289 200380 500547 900662 100783 800821 900-M36 × 3328 700432 500622 800804 400942 800934 200-M39 × 3391 400515000741 600957 9001 1230001 112000-a for the use of thin nuts, it should be considered that the sliding buckle load is lower than the guaranteed load of nuts with full bearing capacity

at the same time, in the guaranteed load test, The new version adds the requirements for the aperture of the fixture used for axial tension or axial compression:

nominal diameter D aperture DH a nominal diameter D aperture DH aminmaxminmaxminmaxm55.0305.115m1414.05014.160m2727.06527.195m66.0306.115m1616.05016.160m3030.06530.195m77.0407.130m1818.05018.160m3333.08033.240m88.0408.130m2020.06520.195m3636.08036.240m1010.04010.130m2222.06522.195m3939.08039.240m1212.05012.160m2 424.06524.195---a DH = D tolerance class D11 (see ISO)

the specific requirements for the thread size of the test mandrel are also provided in the appendix, which guarantees the accuracy of the guaranteed load test. The old standard does not stipulate the size of the test mandrel, so that the requirements for the experimenter to expand the mandrel size are not high, and the use of the new standard can eliminate this phenomenon

nut thread D mandrel (coarse thread) mandrel major diameter (one fourth of the lower limit of 6G tolerance zone) mandrel pitch diameter (tolerance accuracy 5H) nmaxminM32.9012.8742.6762.615M3.53.3853.3543.1103.043M43.8733.8383.5453.474M54.8644.8264.4804.405M65.8395.7945.3505.260M76.8396.7946.3506.260M87.8137.7607.1887.093M109.7919.7329.0268.920M1211.76711.70110.86310.745M1413.75213.68212.70112.576M1615.75215.68214.70114.756M1817.70717.62316.37616.244M2019.70719.62318.37618.244M2221.70721.62320.37620.244M2423.67123.57722.05121.891M2726.67126.57725.05124. 891m3029.62829.52227.72727.557m332.62832.52230.72730.557m3635.58435.46533.40233.222m3938.58438.46536.40236.222

nut thread D × P mandrel (fine thread) mandrel major diameter (one fourth of the lower limit of 6G tolerance zone) mandrel pitch diameter (tolerance accuracy 5H) nmaxminm8 × 17.8397.7947.3507.260M10 × 1.259.8139.7609.1889.093M10 × 19.8399.7949.3509.260M12 × 1.511.79111.73211.02610.914M12 × 1.2511.81311.76011.18811.082M14 × 1.513.79113.73213.02612.911M16 × 1.515.79115.73215.02614.914M18 × 217.75217.68216.70116.569M18 × 1.517.79117.73217.02616.914M20 × 219.75219.68218.70118.569M20 × 1.519.79119.73219.02618.914M22 × 221.75221.68220.70120.569M22 × 1.521.79121.73221.02620.914M24 × 223.75223.68222.70122.569M27 × 226.75226.68225.70125.569M30 × 229.75229.68228.70128.569M33 × 232.75232.68231.70131.569M36 × 335.67135.57734.05133.891M39 × 338.67138.57737.05136.891 the new version also adds a guarantee that the load test speed chuck idling does not exceed 3mm/min. These Provisions on the test fixtures and procedures are to ensure the repeatability and reproducibility of the test. It is proposed to minimize the use of more than the guaranteed load value for the test, which requires the scientific use of nuts. The rest is the same as the original standard

VIII. Hardness performance requirements have been added. Originally, there was only Vickers hardness HV, but now Brinell hardness and Rockwell hardness requirements have been added. The error caused by the original conversion compared with iso4964 is reduced. In addition, the Vickers hardness test force is 98n, i.e. hv10, which changes the original provision of HV30 for arbitration

the new standard makes clear provisions on whether the electromechanical wiring is firmly connected and hardness test. The original provisions did not put forward preparation requirements for routine inspection, but now it is proposed to remove any electroplated coating or other coatings and prepare them appropriately. In addition, in the original case of dispute, the hardness test should be carried out on the longitudinal section passing through the axis of the nut and as close to the major diameter of the thread as possible. Now it is clear that the hardness is determined on the longitudinal section and shown in the figure. It is tested at a position of about 0.5m (half the height of the nut) and as close to the major diameter of the thread as possible

for nuts subject to quenching and tempering treatment, both surface hardness and core height shall meet the requirements of the following two tables. In case of dispute, the Vickers hardness test shall be taken as the arbitration test

for nuts that are not quenched and tempered, the maximum hardness shall not be exceeded. In case of dispute, Vickers hardness test shall be used as the arbitration test. It is also stipulated that under the guarantee load requirements, if the minimum hardness requirements are not met, it cannot be rejected. This replaces the original standard "the minimum hardness is mandatory only for nuts that have been heat treated or nuts whose specifications are too large to guarantee load; it is not mandatory for other nuts and is instructive. For nuts that are not quenched and tempered and can meet the guarantee load test, the minimum hardness should not be used as the basis for rejection." Provisions

hardness properties of coarse thread are as follows:

thread D performance grade Vickers hardness, hvminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxm15 ≤ D ≤ mc353m16 ＜ D ≤ ma353b272 Brinell hardness, hbminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminm5 ≤ D ≤ mc336m16 ＜ D ≤ ma336b259 Rockwell hardness, hrcminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxmin≤ mc36m16 ＜ D ≤ MB26 surface defects shall be in accordance with ISO. The acceptance reference method is Vickers hardness test (see clause 9.2.4). The minimum value of a-thick nut (type 2): 180hv (171hb). B. maximum value of thick nut (type 2): 302hv (287hb; 30hrc)

hardness performance requirements of fine thread are as follows:

thread D × P performance grade Vickers hardness, hvminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxmm8 × 1≤D≤M16 × 1. a353 b295 cM16 × 1.5＜D≤M39 ×-- Brinell hardness, hbminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxmm8 × 1≤D≤M16 × 1. a336 b280 cM16 × 1.5＜D≤M39 ×-- Rockwell hardness, hrcminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxminmaxmm8 × 1≤D≤M16 × 1.. 2 a36 b29 c362936M16 × 1.5＜D≤M39 × 3--29.23624-- surface defects shall be in accordance with ISO. The acceptance reference method is Vickers hardness test (see clause 9.2.4). The minimum value of a-thick nut (type 2): 195hv (185hb). B. maximum value of thick nut (type 2): 302hv (287hb; 30hrc) minimum value of thick nut (type 2): 250hv (238hb; 22.2hrc) IX. on the sign, in the clock method symbol, the original "cannot replace the origin with the manufacturer's identification mark" is changed to "the manufacturer's mark or dot mark should be used at the 12o'clock position (reference mark)." It is also clearly stipulated that thin nuts cannot be marked by the clock plane method

X. the new standard also puts forward requirements for packaging marks, which should include manufacturers and/or pins