{"id":100042,"date":"2026-02-15T20:07:58","date_gmt":"2026-02-15T20:07:58","guid":{"rendered":"https:\/\/vibromera.eu\/?post_type=calculator&#038;p=100042"},"modified":"2026-02-15T20:07:58","modified_gmt":"2026-02-15T20:07:58","slug":"bolt-strength-class-iso898","status":"publish","type":"calculator","link":"https:\/\/vibromera.eu\/bn\/calculators\/bolt-strength-class-iso898\/","title":{"rendered":"\u09ac\u09cb\u09b2\u09cd\u099f \u09b6\u0995\u09cd\u09a4\u09bf \u09b6\u09cd\u09b0\u09c7\u09a3\u09c0 (4.6\u201312.9) | ISO 898-1 \u09b0\u09c7\u09ab\u09be\u09b0\u09c7\u09a8\u09cd\u09b8"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"WebApplication\",\"name\":\"Bolt Strength Classes Calculator\",\"alternateName\":[\"ISO 898-1 Bolt Grade Reference\",\"Bolt Property Class Calculator\",\"Proof Load Calculator\"],\"description\":\"Free online engineering reference for bolt property classes per ISO 898-1. Look up tensile strength Rm, yield strength Rp0.2, proof stress Sp, hardness, and calculate proof load for classes 4.6 to 12.9.\",\"url\":\"https:\/\/vibromera.eu\/calculators\/bolt-strength-class-iso898\/\",\"applicationCategory\":\"Engineering Calculator\",\"operatingSystem\":\"Any (Web Browser)\",\"offers\":{\"@type\":\"Offer\",\"price\":\"0\",\"priceCurrency\":\"EUR\"},\"creator\":{\"@type\":\"Organization\",\"name\":\"Vibromera\",\"url\":\"https:\/\/vibromera.eu\/\"},\"datePublished\":\"2025-01-01\",\"dateModified\":\"2025-02-14\",\"inLanguage\":\"en\",\"isAccessibleForFree\":true,\"featureList\":[\"Property classes 4.6 to 12.9\",\"Proof load calculation\",\"Metric threads M3\u2013M48\",\"ISO 898-1 compliant data\",\"Auto-calculation on input change\",\"Full comparison table\"],\"keywords\":\"bolt strength, ISO 898-1, property class, proof load, tensile strength, Rp0.2, 8.8, 10.9, 12.9\"}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[\n{\"@type\":\"Question\",\"name\":\"What do the two numbers in a bolt class like 8.8 mean?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"The first number \u00d7 100 gives the nominal tensile strength Rm in MPa. The second number \u00d7 first number \u00d7 10 gives the nominal yield strength Rp0.2 in MPa. For class 8.8: Rm = 8 \u00d7 100 = 800 MPa and Rp0.2 = 8 \u00d7 8 \u00d7 10 = 640 MPa.\"}},\n{\"@type\":\"Question\",\"name\":\"What is the difference between Rp0.2 and Sp (proof stress)?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Rp0.2 is the 0.2% offset yield strength \u2014 the stress at which the bolt takes a 0.2% permanent set. Sp (proof stress) is a guaranteed minimum stress the bolt must withstand without permanent deformation. Sp is typically 90\u201395% of Rp0.2 and is used to calculate the proof load for quality testing.\"}},\n{\"@type\":\"Question\",\"name\":\"When should I use 10.9 versus 8.8 bolts?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Use 8.8 for general-purpose applications \u2014 it offers good strength with ductility. Use 10.9 when higher clamping force is needed in a limited space, such as automotive engine assemblies, structural steel connections, or high-vibration environments. 12.9 is reserved for the most demanding applications where maximum preload per bolt is essential.\"}},\n{\"@type\":\"Question\",\"name\":\"How are bolt grades marked on the bolt head?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Per ISO 898-1, hexagon bolts and screws must be permanently marked on the head (top or side) with the property class designation (e.g., 8.8, 10.9, 12.9) and the manufacturer's identification mark. Socket head cap screws may be marked on the side of the head or on the recess.\"}},\n{\"@type\":\"Question\",\"name\":\"How is proof load calculated?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Proof load Fp = Sp \u00d7 As, where Sp is the proof stress (MPa) for the property class and As is the tensile stress area (mm\u00b2) for the thread size. The result is in Newtons (N). Divide by 1000 for kN. For example, an M12 class 8.8 bolt: Fp = 580 \u00d7 84.3 = 48,894 N \u2248 48.9 kN.\"}}\n]}\n<\/script>\n\n<script type=\"application\/ld+json\">\n{\"@context\":\"https:\/\/schema.org\",\"@type\":\"BreadcrumbList\",\"itemListElement\":[\n{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/vibromera.eu\/\"},\n{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Calculators\",\"item\":\"https:\/\/vibromera.eu\/calculators\/\"},\n{\"@type\":\"ListItem\",\"position\":3,\"name\":\"Bolt Strength Classes\",\"item\":\"https:\/\/vibromera.eu\/calculators\/bolt-strength-class-iso898\/\"}\n]}\n<\/script>\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.googleapis.com\">\n\n<link rel=\"preconnect\" href=\"https:\/\/fonts.gstatic.com\" crossorigin>\n\n<link 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}\n    .vc-faq-a { max-height:none!important; }\n    .vc-results { max-height:none!important; padding:24px!important; }\n    .vc-copy-btn, .vc-section-chevron, .vc-faq-chevron, .vc-presets, .vc-promo { display:none!important; }\n}\n<\/style>\n\n<div class=\"vc-calculator\" id=\"vc-bolt-strength\">\n\n<!-- Header -->\n<header class=\"vc-header\">\n    <p class=\"vc-header-eyebrow\">Free Engineering Tool<\/p>\n    <h1 class=\"vc-header-title\">Bolt Strength Classes (4.6\u201312.9)<\/h1>\n    <p class=\"vc-header-subtitle\">Look up mechanical properties for any bolt property class per ISO 898-1 \u2014 tensile strength, yield strength, proof stress, hardness \u2014 and calculate proof load for any metric thread size.<\/p>\n    <div class=\"vc-badges\">\n        <span class=\"vc-badge\">ISO 898-1<\/span>\n        <span class=\"vc-badge\">Classes 4.6 \u2013 12.9<\/span>\n        <span class=\"vc-badge\">M3 \u2013 M48<\/span>\n    <\/div>\n<\/header>\n\n<!-- Calculator Card -->\n<div class=\"vc-card\">\n    <form class=\"vc-form\" id=\"vc-form\" autocomplete=\"off\">\n        <div class=\"vc-form-grid\">\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-class\">Property Class<\/label>\n                <select class=\"vc-select\" id=\"vc-class\">\n                    <option value=\"4.6\">4.6 \u2014 Low carbon steel<\/option>\n                    <option value=\"4.8\">4.8 \u2014 Low carbon steel<\/option>\n                    <option value=\"5.6\">5.6 \u2014 Medium carbon steel<\/option>\n                    <option value=\"5.8\">5.8 \u2014 Low carbon steel<\/option>\n                    <option value=\"6.8\">6.8 \u2014 Low carbon steel<\/option>\n                    <option value=\"8.8\" selected>8.8 \u2014 Medium carbon Q&#038;T<\/option>\n                    <option value=\"9.8\">9.8 \u2014 Medium carbon Q&#038;T<\/option>\n                    <option value=\"10.9\">10.9 \u2014 Alloy steel Q&#038;T<\/option>\n                    <option value=\"12.9\">12.9 \u2014 Alloy steel Q&#038;T<\/option>\n                <\/select>\n            <\/div>\n            <div class=\"vc-field\">\n                <label class=\"vc-label\" for=\"vc-bolt\">Bolt Size <span class=\"vc-label-hint\">(for proof load)<\/span><\/label>\n                <select class=\"vc-select\" id=\"vc-bolt\"><\/select>\n            <\/div>\n        <\/div>\n\n        <!-- Presets -->\n        <div class=\"vc-presets\">\n            <div class=\"vc-presets-label\">Quick presets<\/div>\n            <button type=\"button\" class=\"vc-preset-btn\" data-class=\"8.8\" data-bolt=\"M12\">8.8 M12<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-class=\"10.9\" data-bolt=\"M16\">10.9 M16<\/button>\n            <button type=\"button\" class=\"vc-preset-btn\" data-class=\"12.9\" data-bolt=\"M20\">12.9 M20<\/button>\n        <\/div>\n    <\/form>\n\n    <!-- Results -->\n    <div class=\"vc-results vc-visible\" id=\"vc-results\">\n        <div class=\"vc-results-head\">\n            <h2 class=\"vc-results-title\">Results<\/h2>\n            <button type=\"button\" class=\"vc-copy-btn\" id=\"vc-copy-btn\">\n                <svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg>\n                Copy\n            <\/button>\n        <\/div>\n        <div class=\"vc-result-grid\">\n            <div class=\"vc-rcard vc-rcard-primary\">\n                <div class=\"vc-rcard-label\">Proof Load Fp<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-fp\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Tensile Strength Rm<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-rm\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Yield Strength Rp0.2<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-rp\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Proof Stress Sp<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-sp\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Stress Area As<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-as\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Elongation at Break<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-elong\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Hardness HRC<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-hrc\">\u2014<\/div>\n            <\/div>\n            <div class=\"vc-rcard\">\n                <div class=\"vc-rcard-label\">Ultimate Tensile Load<\/div>\n                <div class=\"vc-rcard-value\" id=\"vc-r-ft\">\u2014<\/div>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Comparison Table -->\n<div class=\"vc-section vc-open\" id=\"vc-sec-table\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"true\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\ud83d\udcca<\/span>\n            <span class=\"vc-section-title\">Full Comparison Table \u2014 All Classes<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner\">\n            <div class=\"vc-table-wrap\">\n                <table class=\"vc-table\" id=\"vc-comp-table\">\n                    <thead><tr><th>Class<\/th><th>Rm (MPa)<\/th><th>Rp0.2 (MPa)<\/th><th>Sp (MPa)<\/th><th>Elong. %<\/th><th>HRC<\/th><th>Material<\/th><\/tr><\/thead>\n                    <tbody id=\"vc-tbody-comp\"><\/tbody>\n                <\/table>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Theory & Formulas -->\n<div class=\"vc-section\" id=\"vc-sec-theory\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\ud83d\udcd8<\/span>\n            <span class=\"vc-section-title\">Theory &amp; Formulas<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner vc-theory\">\n            <h3>Reading the Property Class Designation<\/h3>\n            <p>The two-number system (e.g., 8.8) encodes the bolt&#8217;s key mechanical properties:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-1\"><\/div>\n            <div class=\"vc-formula-box\" id=\"vc-katex-2\"><\/div>\n            <p>For class <strong>8.8<\/strong>: R<sub>m<\/sub> = 8 \u00d7 100 = 800 MPa, R<sub>p0.2<\/sub> = 8 \u00d7 8 \u00d7 10 = 640 MPa.<\/p>\n\n            <h3>Proof Load Calculation<\/h3>\n            <p>The proof load is the maximum force a bolt must withstand without permanent deformation:<\/p>\n            <div class=\"vc-formula-box\" id=\"vc-katex-3\"><\/div>\n            <p>Where S<sub>p<\/sub> is the proof stress and A<sub>s<\/sub> is the tensile stress area per ISO 898-1.<\/p>\n\n            <h3>Ultimate Tensile Load<\/h3>\n            <div class=\"vc-formula-box\" id=\"vc-katex-4\"><\/div>\n\n            <div class=\"vc-example-box\">\n                <div class=\"vc-example-title\">Example \u2014 M12 Class 8.8 Bolt<\/div>\n                <p><strong>Given:<\/strong> Class 8.8, M12 (A<sub>s<\/sub> = 84.3 mm\u00b2), d \u2264 16 mm \u2192 S<sub>p<\/sub> = 580 MPa<\/p>\n                <p>Proof load F<sub>p<\/sub> = 580 \u00d7 84.3 = <strong>48,894 N \u2248 48.9 kN<\/strong><\/p>\n                <p>Tensile load F<sub>t<\/sub> = 800 \u00d7 84.3 = <strong>67,440 N \u2248 67.4 kN<\/strong><\/p>\n            <\/div>\n\n            <div class=\"vc-warning-box\">\n                <p style=\"margin:0;font-size:14px;color:var(--vc-ink-secondary);\"><strong>\u26a0\ufe0f Note:<\/strong> For class 8.8, S<sub>p<\/sub> = 580 MPa for d \u2264 16 mm and S<sub>p<\/sub> = 600 MPa for d &gt; 16 mm. This is because larger bolts have a higher ratio of hardenable to total cross-section.<\/p>\n            <\/div>\n\n            <div class=\"vc-info-box\">\n                <p><strong>\u2139\ufe0f Design tip:<\/strong> Typical bolt preload target is 75\u201390% of proof load. Never exceed proof load during tightening. Use calibrated torque wrenches or angle-controlled tightening for critical joints.<\/p>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Related Calculators -->\n<div class=\"vc-section\" id=\"vc-sec-related\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\ud83d\udd17<\/span>\n            <span class=\"vc-section-title\">Related Calculators<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner\">\n            <div class=\"vc-related\">\n                <a class=\"vc-related-link\" href=\"\/calculators\/metric-thread-dimensions\/\">Metric Thread Dimensions (ISO 261)<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/o-ring-selection-iso3601\/\">O-Ring Selection (ISO 3601)<\/a>\n                <a class=\"vc-related-link\" href=\"\/calculators\/residual-unbalance-iso1940\/\">Residual Unbalance (ISO 1940)<\/a>\n            <\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- FAQ -->\n<div class=\"vc-section\" id=\"vc-sec-faq\">\n    <button type=\"button\" class=\"vc-section-toggle\" aria-expanded=\"false\">\n        <span class=\"vc-section-toggle-text\">\n            <span class=\"vc-section-icon\">\u2753<\/span>\n            <span class=\"vc-section-title\">Frequently Asked Questions<\/span>\n        <\/span>\n        <svg class=\"vc-section-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg>\n    <\/button>\n    <div class=\"vc-section-body\">\n        <div class=\"vc-section-inner\">\n            <div class=\"vc-faq-list\" id=\"vc-faq-list\"><\/div>\n        <\/div>\n    <\/div>\n<\/div>\n\n<!-- Promo -->\n<div class=\"vc-promo\">\n    <div class=\"vc-promo-text\">\n        <strong>Vibromera \u2014 Portable Balancing &amp; Vibration Analysis<\/strong><br>\n        Professional field balancing instruments and software. Used in 50+ countries.\n    <\/div>\n    <a class=\"vc-promo-link\" href=\"https:\/\/vibromera.eu\/\" target=\"_blank\" rel=\"noopener\">Learn More<\/a>\n<\/div>\n\n<!-- Footer -->\n<footer class=\"vc-footer\">\n    <p>&copy; 2024\u20132025 <a href=\"https:\/\/vibromera.eu\/\">Vibromera<\/a> \u2014 Engineering Calculators<\/p>\n    <p style=\"font-size:12px;margin-top:4px;\">Based on ISO 898-1. Last updated: February 2025<\/p>\n    <div class=\"vc-footer-links\">\n        <a href=\"\/calculators\/engineering-calculators\/\">All Calculators<\/a>\n        <a href=\"https:\/\/vibromera.eu\/contacts\/\">Contact<\/a>\n    <\/div>\n<\/footer>\n\n<\/div>\n\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/katex@0.16.11\/dist\/katex.min.js\"><\/script>\n<script>\n(function() {\n    'use strict';\n\n    var SLUG = 'bolt-strength-class-iso898';\n\n    function $(id) { return document.getElementById(id); }\n    function fmt(n, d) { if (isNaN(n)) return '\\u2014'; var f = n.toFixed(d === undefined ? 1 : d); return f.replace(\/(\\.\\d*?)0+$\/, '$1').replace(\/\\.$\/, ''); }\n    function fmtN(n) { if (isNaN(n)) return '\\u2014'; return n >= 1000 ? n.toFixed(0).replace(\/\\B(?=(\\d{3})+(?!\\d))\/g, ',') : fmt(n, 0); }\n\n    \/* \u2500\u2500 THREAD DATA \u2500\u2500 *\/\n    \/\/ [label, d, P] \u2014 coarse pitch\n    var THREADS = [\n        ['M3',  3,  0.5],\n        ['M4',  4,  0.7],\n        ['M5',  5,  0.8],\n        ['M6',  6,  1.0],\n        ['M8',  8,  1.25],\n        ['M10', 10, 1.5],\n        ['M12', 12, 1.75],\n        ['M14', 14, 2.0],\n        ['M16', 16, 2.0],\n        ['M20', 20, 2.5],\n        ['M24', 24, 3.0],\n        ['M30', 30, 3.5],\n        ['M36', 36, 4.0],\n        ['M42', 42, 4.5],\n        ['M48', 48, 5.0]\n    ];\n\n    function calcAs(d, P) {\n        var d2 = d - 0.6495191 * P;\n        var d3 = d - 1.2268693 * P;\n        var dm = (d2 + d3) \/ 2;\n        return Math.PI \/ 4 * dm * dm;\n    }\n\n    \/* \u2500\u2500 PROPERTY CLASS DATA \u2500\u2500 *\/\n    \/\/ { Rm, Rp, Sp, SpHigh (for d>16), elong, hrcMin, hrcMax, material }\n    var CLASSES = {\n        '4.6':  { Rm:400,  Rp:240,  Sp:225,  SpHigh:null, elong:22, hrcMin:null, hrcMax:null, mat:'Low carbon steel' },\n        '4.8':  { Rm:420,  Rp:340,  Sp:310,  SpHigh:null, elong:null, hrcMin:null, hrcMax:null, mat:'Low carbon steel' },\n        '5.6':  { Rm:500,  Rp:300,  Sp:280,  SpHigh:null, elong:null, hrcMin:null, hrcMax:null, mat:'Medium carbon steel' },\n        '5.8':  { Rm:520,  Rp:420,  Sp:380,  SpHigh:null, elong:null, hrcMin:null, hrcMax:null, mat:'Low carbon steel' },\n        '6.8':  { Rm:600,  Rp:480,  Sp:440,  SpHigh:null, elong:null, hrcMin:null, hrcMax:null, mat:'Low carbon steel' },\n        '8.8':  { Rm:800,  Rp:640,  Sp:580,  SpHigh:600,  elong:12, hrcMin:22, hrcMax:32, mat:'Medium carbon steel, Q&T' },\n        '9.8':  { Rm:900,  Rp:720,  Sp:650,  SpHigh:null, elong:null, hrcMin:null, hrcMax:null, mat:'Medium carbon steel, Q&T' },\n        '10.9': { Rm:1040, Rp:940,  Sp:830,  SpHigh:null, elong:9, hrcMin:32, hrcMax:39, mat:'Alloy steel, Q&T' },\n        '12.9': { Rm:1220, Rp:1100, Sp:970,  SpHigh:null, elong:8, hrcMin:39, hrcMax:44, mat:'Alloy steel, Q&T' }\n    };\n\n    \/* \u2500\u2500 BUILD BOLT DROPDOWN \u2500\u2500 *\/\n    function buildBoltDropdown() {\n        var sel = $('vc-bolt');\n        THREADS.forEach(function(t) {\n            var As = calcAs(t[1], t[2]);\n            var opt = document.createElement('option');\n            opt.value = t[0];\n            opt.textContent = t[0] + '  (As=' + fmt(As, 1) + ' mm\\u00b2)';\n            sel.appendChild(opt);\n        });\n        sel.value = 'M12';\n    }\n\n    \/* \u2500\u2500 BUILD COMPARISON TABLE \u2500\u2500 *\/\n    function buildCompTable() {\n        var tbody = $('vc-tbody-comp');\n        var classOrder = ['4.6','4.8','5.6','5.8','6.8','8.8','9.8','10.9','12.9'];\n        classOrder.forEach(function(cls) {\n            var c = CLASSES[cls];\n            var tr = document.createElement('tr');\n            tr.setAttribute('data-class', cls);\n            var spText = c.Sp + (c.SpHigh ? ' \/ ' + c.SpHigh : '');\n            var elongText = c.elong ? c.elong + '%' : '\\u2014';\n            var hrcText = (c.hrcMin !== null) ? c.hrcMin + '\u2013' + c.hrcMax : '\\u2014';\n            tr.innerHTML =\n                '<td><strong>' + cls + '<\/strong><\/td>' +\n                '<td class=\"vc-mono-cell\">' + c.Rm + '<\/td>' +\n                '<td class=\"vc-mono-cell\">' + c.Rp + '<\/td>' +\n                '<td class=\"vc-mono-cell\">' + spText + '<\/td>' +\n                '<td class=\"vc-mono-cell\">' + elongText + '<\/td>' +\n                '<td class=\"vc-mono-cell\">' + hrcText + '<\/td>' +\n                '<td>' + c.mat + '<\/td>';\n            tbody.appendChild(tr);\n        });\n    }\n\n    \/* \u2500\u2500 GET THREAD DATA \u2500\u2500 *\/\n    function getThread(label) {\n        for (var i = 0; i < THREADS.length; i++) {\n            if (THREADS[i][0] === label) return THREADS[i];\n        }\n        return null;\n    }\n\n    \/* \u2500\u2500 CALCULATE \u2500\u2500 *\/\n    function calculate() {\n        var cls = $('vc-class').value;\n        var boltLabel = $('vc-bolt').value;\n        var c = CLASSES[cls];\n        var t = getThread(boltLabel);\n        if (!c || !t) return;\n\n        var d = t[1], P = t[2];\n        var As = calcAs(d, P);\n\n        \/\/ Determine Sp based on diameter\n        var Sp = c.Sp;\n        if (c.SpHigh && d > 16) Sp = c.SpHigh;\n\n        var Fp = Sp * As;     \/\/ Proof load (N)\n        var Ft = c.Rm * As;   \/\/ Ultimate tensile load (N)\n\n        $('vc-r-fp').innerHTML = fmtN(Fp \/ 1000) + ' <span class=\"vc-rcard-unit\">kN<\/span> <span class=\"vc-rcard-unit\">(' + fmtN(Fp) + ' N)<\/span>';\n        $('vc-r-rm').innerHTML = c.Rm + ' <span class=\"vc-rcard-unit\">MPa<\/span>';\n        $('vc-r-rp').innerHTML = c.Rp + ' <span class=\"vc-rcard-unit\">MPa<\/span>';\n        $('vc-r-sp').innerHTML = Sp + ' <span class=\"vc-rcard-unit\">MPa<\/span>' + (c.SpHigh ? ' <span class=\"vc-rcard-unit\">(d' + (d > 16 ? '>' : '\\u226416') + 'mm)<\/span>' : '');\n        $('vc-r-as').innerHTML = fmt(As, 1) + ' <span class=\"vc-rcard-unit\">mm\\u00b2<\/span>';\n        $('vc-r-elong').innerHTML = c.elong ? c.elong + ' <span class=\"vc-rcard-unit\">%<\/span>' : '\\u2014';\n        $('vc-r-hrc').innerHTML = (c.hrcMin !== null) ? c.hrcMin + '\u2013' + c.hrcMax + ' <span class=\"vc-rcard-unit\">HRC<\/span>' : '\\u2014';\n        $('vc-r-ft').innerHTML = fmtN(Ft \/ 1000) + ' <span class=\"vc-rcard-unit\">kN<\/span> <span class=\"vc-rcard-unit\">(' + fmtN(Ft) + ' N)<\/span>';\n\n        $('vc-results').classList.add('vc-visible');\n\n        \/\/ Highlight in comparison table\n        var rows = document.querySelectorAll('#vc-tbody-comp tr');\n        rows.forEach(function(row) {\n            row.classList.toggle('vc-highlight', row.getAttribute('data-class') === cls);\n        });\n\n        \/\/ URL params\n        var u = new URL(window.location);\n        u.searchParams.set('class', cls);\n        u.searchParams.set('bolt', boltLabel);\n        history.replaceState(null, '', u.toString());\n\n        saveHistory({ class: cls, bolt: boltLabel, _summary: 'Class ' + cls + ' ' + boltLabel + ', Fp=' + fmtN(Fp \/ 1000) + ' kN' });\n    }\n\n    \/* \u2500\u2500 PRESETS \u2500\u2500 *\/\n    document.querySelectorAll('.vc-preset-btn').forEach(function(btn) {\n        btn.addEventListener('click', function(e) {\n            e.preventDefault();\n            $('vc-class').value = this.getAttribute('data-class');\n            $('vc-bolt').value = this.getAttribute('data-bolt');\n            calculate();\n        });\n    });\n\n    \/* \u2500\u2500 AUTO-CALCULATE \u2500\u2500 *\/\n    $('vc-form').addEventListener('input', calculate);\n    $('vc-form').addEventListener('change', calculate);\n\n    \/* \u2500\u2500 COPY \u2500\u2500 *\/\n    $('vc-copy-btn').addEventListener('click', function() {\n        var text = 'Bolt Strength Class \u2014 ISO 898-1\\n' +\n            '\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\n' +\n            'Class: ' + $('vc-class').value + '\\n' +\n            'Bolt: ' + $('vc-bolt').value + '\\n' +\n            'Rm: ' + $('vc-r-rm').textContent + '\\n' +\n            'Rp0.2: ' + $('vc-r-rp').textContent + '\\n' +\n            'Sp: ' + $('vc-r-sp').textContent + '\\n' +\n            'Stress area As: ' + $('vc-r-as').textContent + '\\n' +\n            'Proof load Fp: ' + $('vc-r-fp').textContent + '\\n' +\n            'Tensile load Ft: ' + $('vc-r-ft').textContent + '\\n' +\n            'Hardness: ' + $('vc-r-hrc').textContent + '\\n' +\n            '\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\u2501\\n' +\n            'vibromera.eu\/calculators\/bolt-strength-class-iso898\/';\n\n        if (navigator.clipboard) {\n            navigator.clipboard.writeText(text).then(function() {\n                var btn = $('vc-copy-btn');\n                btn.classList.add('vc-copied');\n                btn.innerHTML = '<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><polyline points=\"20 6 9 17 4 12\"\/><\/svg> Copied!';\n                setTimeout(function() {\n                    btn.classList.remove('vc-copied');\n                    btn.innerHTML = '<svg width=\"14\" height=\"14\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><rect x=\"9\" y=\"9\" width=\"13\" height=\"13\" rx=\"2\"\/><path d=\"M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1\"\/><\/svg> Copy';\n                }, 2000);\n            });\n        }\n    });\n\n    \/* \u2500\u2500 COLLAPSIBLE SECTIONS \u2500\u2500 *\/\n    document.querySelectorAll('.vc-section-toggle').forEach(function(btn) {\n        btn.addEventListener('click', function() {\n            var section = this.closest('.vc-section');\n            var isOpen = section.classList.contains('vc-open');\n            section.classList.toggle('vc-open');\n            this.setAttribute('aria-expanded', !isOpen);\n        });\n    });\n\n    \/* \u2500\u2500 FAQ \u2500\u2500 *\/\n    var faqData = [\n        { q: 'What do the two numbers in a bolt class like 8.8 mean?', a: '<p>The designation is a coded system per ISO 898-1:<\/p><ul><li><strong>First number \\u00d7 100<\/strong> = nominal tensile strength R<sub>m<\/sub> in MPa<\/li><li><strong>First \\u00d7 second \\u00d7 10<\/strong> = nominal yield strength R<sub>p0.2<\/sub> in MPa<\/li><\/ul><p>For class <strong>8.8<\/strong>: R<sub>m<\/sub> = 8 \\u00d7 100 = 800 MPa, R<sub>p0.2<\/sub> = 8 \\u00d7 8 \\u00d7 10 = 640 MPa.<\/p><p>The second digit thus represents the yield-to-tensile ratio (0.8 = 80%).<\/p>' },\n        { q: 'What is the difference between Rp0.2 and Sp (proof stress)?', a: '<p><strong>R<sub>p0.2<\/sub><\/strong> (yield strength) is the stress causing 0.2% permanent elongation \u2014 determined by tensile testing.<\/p><p><strong>S<sub>p<\/sub><\/strong> (proof stress) is a lower, guaranteed minimum stress the bolt must withstand with zero permanent set \u2014 used for proof load testing per ISO 898-1.<\/p><p>Typically S<sub>p<\/sub> \\u2248 90\\u201395% of R<sub>p0.2<\/sub>. The proof load F<sub>p<\/sub> = S<sub>p<\/sub> \\u00d7 A<sub>s<\/sub> is the key parameter for bolt specification.<\/p>' },\n        { q: 'When should I use 10.9 versus 8.8 bolts?', a: '<p><strong>8.8<\/strong> is the most common class for general engineering:<\/p><ul><li>Good strength (R<sub>m<\/sub> = 800 MPa) with adequate ductility<\/li><li>Suitable for most machine frames, flanges, brackets<\/li><li>Cost-effective, readily available<\/li><\/ul><p><strong>10.9<\/strong> is used when higher clamp force is needed:<\/p><ul><li>Automotive engine\/chassis (OEM standard)<\/li><li>Structural steel connections (EN 14399)<\/li><li>High-vibration environments requiring higher preload<\/li><li>Space-constrained joints (smaller bolt, same force)<\/li><\/ul><p><strong>12.9<\/strong> is for the most demanding applications where maximum preload per bolt is critical, e.g. precision machinery, motorsport.<\/p>' },\n        { q: 'How are bolt grades marked on the bolt head?', a: '<p>Per ISO 898-1, hex bolts must be permanently marked with:<\/p><ul><li><strong>Property class<\/strong> \u2014 e.g. \"8.8\", \"10.9\", \"12.9\"<\/li><li><strong>Manufacturer\\u2019s ID<\/strong> \u2014 symbol or code<\/li><\/ul><p>Marking location: top or side of hex head. Socket head cap screws: side of head or in the recess.<\/p><p>Unmarked bolts should be assumed \\u2264 class 4.6 and must not be used in structural applications.<\/p>' },\n        { q: 'How is proof load calculated?', a: '<p>Proof load F<sub>p<\/sub> = S<sub>p<\/sub> \\u00d7 A<sub>s<\/sub><\/p><ul><li><strong>S<sub>p<\/sub><\/strong> = proof stress (MPa) from ISO 898-1 for the chosen property class<\/li><li><strong>A<sub>s<\/sub><\/strong> = tensile stress area (mm\\u00b2) for the thread size per ISO 898-1<\/li><li>Result is in <strong>Newtons<\/strong> (\\u00f7 1000 for kN)<\/li><\/ul><p>The proof load test per ISO 898-1 applies this force axially for 15 seconds. The bolt must not show permanent elongation.<\/p>' }\n    ];\n\n    var faqList = $('vc-faq-list');\n    faqData.forEach(function(faq) {\n        faqList.innerHTML += '<div class=\"vc-faq-item\"><button type=\"button\" class=\"vc-faq-q\"><span>' + faq.q + '<\/span><svg class=\"vc-faq-chevron\" viewBox=\"0 0 24 24\" fill=\"none\" stroke=\"currentColor\" stroke-width=\"2\"><path d=\"M6 9l6 6 6-6\"\/><\/svg><\/button><div class=\"vc-faq-a\"><div class=\"vc-faq-a-inner\">' + faq.a + '<\/div><\/div><\/div>';\n    });\n    faqList.addEventListener('click', function(e) {\n        var btn = e.target.closest('.vc-faq-q');\n        if (!btn) return;\n        btn.closest('.vc-faq-item').classList.toggle('vc-open');\n    });\n\n    \/* \u2500\u2500 HISTORY \u2500\u2500 *\/\n    function saveHistory(entry) {\n        var key = 'vc_history_' + SLUG;\n        var arr = [];\n        try { arr = JSON.parse(localStorage.getItem(key)) || []; } catch(e) {}\n        entry._ts = new Date().toISOString();\n        arr.unshift(entry);\n        if (arr.length > 10) arr = arr.slice(0, 10);\n        try { localStorage.setItem(key, JSON.stringify(arr)); } catch(e) {}\n    }\n\n    \/* \u2500\u2500 URL PARAMS \u2500\u2500 *\/\n    function loadParams() {\n        var p = new URLSearchParams(window.location.search);\n        if (p.has('class')) $('vc-class').value = p.get('class');\n        if (p.has('bolt')) $('vc-bolt').value = p.get('bolt');\n    }\n\n    \/* \u2500\u2500 KATEX \u2500\u2500 *\/\n    function renderFormulas() {\n        try {\n            katex.render('R_m \\\\;=\\\\; \\\\text{1st digit} \\\\times 100 \\\\quad [\\\\text{MPa}]', $('vc-katex-1'), { displayMode: true, throwOnError: false });\n            katex.render('R_{p0.2} \\\\;=\\\\; \\\\text{1st digit} \\\\times \\\\text{2nd digit} \\\\times 10 \\\\quad [\\\\text{MPa}]', $('vc-katex-2'), { displayMode: true, throwOnError: false });\n            katex.render('F_p = S_p \\\\times A_s \\\\quad [\\\\text{N}]', $('vc-katex-3'), { displayMode: true, throwOnError: false });\n            katex.render('F_t = R_m \\\\times A_s \\\\quad [\\\\text{N}]', $('vc-katex-4'), { displayMode: true, throwOnError: false });\n        } catch(e) {}\n    }\n\n    \/* \u2500\u2500 INIT \u2500\u2500 *\/\n    function init() {\n        buildBoltDropdown();\n        buildCompTable();\n        loadParams();\n        renderFormulas();\n        calculate();\n    }\n\n    if (document.readyState === 'loading') {\n        document.addEventListener('DOMContentLoaded', init);\n    } else {\n        init();\n    }\n})();\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>ISO 898-1 \u0985\u09a8\u09c1\u09af\u09be\u09af\u09bc\u09c0 \u09ac\u09cb\u09b2\u09cd\u099f \u09b8\u09ae\u09cd\u09aa\u09a4\u09cd\u09a4\u09bf \u09b6\u09cd\u09b0\u09c7\u09a3\u09c0\u09b0 \u099c\u09a8\u09cd\u09af \u09ac\u09bf\u09a8\u09be\u09ae\u09c2\u09b2\u09cd\u09af\u09c7 \u0985\u09a8\u09b2\u09be\u0987\u09a8 \u09b0\u09c7\u09ab\u09be\u09b0\u09c7\u09a8\u09cd\u09b8\u0964 Rm, Rp0.2, \u09aa\u09cd\u09b0\u09ae\u09be\u09a3 \u099a\u09be\u09aa Sp, \u0995\u09a0\u09cb\u09b0\u09a4\u09be \u09a6\u09c7\u0996\u09c1\u09a8 \u098f\u09ac\u0982 \u09af\u09c7\u0995\u09cb\u09a8\u09cb \u09ae\u09c7\u099f\u09cd\u09b0\u09bf\u0995 \u09a5\u09cd\u09b0\u09c7\u09a1 M3\u2013M48 \u098f\u09b0 \u09b8\u09be\u09a5\u09c7 \u09b6\u09cd\u09b0\u09c7\u09a3\u09c0 4.6 \u09a5\u09c7\u0995\u09c7 12.9 \u098f\u09b0 \u099c\u09a8\u09cd\u09af \u09aa\u09cd\u09b0\u09ae\u09be\u09a3 \u09b2\u09cb\u09a1 \u0997\u09a3\u09a8\u09be \u0995\u09b0\u09c1\u09a8\u0964<\/p>","protected":false},"featured_media":0,"template":"","meta":{"ai_generated_summary":"","footnotes":""},"categories":[],"tags":[],"class_list":["post-100042","calculator","type-calculator","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator\/100042","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator"}],"about":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/types\/calculator"}],"version-history":[{"count":1,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator\/100042\/revisions"}],"predecessor-version":[{"id":100353,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/calculator\/100042\/revisions\/100353"}],"wp:attachment":[{"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/media?parent=100042"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/categories?post=100042"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vibromera.eu\/bn\/wp-json\/wp\/v2\/tags?post=100042"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}