{"id":3673,"date":"2026-11-12T20:21:42","date_gmt":"2026-11-12T12:21:42","guid":{"rendered":"https:\/\/aft-machining.com\/?p=3673"},"modified":"2026-11-12T20:23:08","modified_gmt":"2026-11-12T12:23:08","slug":"machined-forging-drawing-tolerances","status":"publish","type":"post","link":"https:\/\/aft-machining.com\/en\/machined-forging-drawing-tolerances\/","title":{"rendered":"Tolerances for Machined Forgings: How to Split ISO 2768, EN 586-3 and GD&amp;T on One Drawing"},"content":{"rendered":"\n\n\n<style>\n.afm-wrap{--o:#E85C2E;--od:#C2410C;--ob:#FFF4EE;--obd:#F6C8B2;--bg2:#F8F8F8;--line:#E6E6E6;--tx:#2B2B2B;--hd:#1A1A1A;--mu:#5A5A5A;background:#FFFFFF !important;border-radius:14px;padding:44px 48px 8px;margin:0 0 32px;}\n.afm-wrap .afm-article{max-width:none;width:100%;margin:0;padding:0 0 40px;color:var(--tx) !important;font-family:Inter,\"Noto Sans TC\",\"PingFang TC\",\"Microsoft 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summary::after{content:\"+\";position:absolute;right:20px;top:12px;color:var(--o);font-size:24px;font-weight:700;line-height:1.2;}\n.afm-wrap .afm-faq details[open] summary{background:var(--ob);border-radius:12px 12px 0 0;}\n.afm-wrap .afm-faq details[open] summary::after{content:\"\\2212\";}\n.afm-wrap .afm-article .afm-faq summary h3{display:inline;margin:0;padding:0;font-size:inherit;color:inherit !important;font-weight:inherit;line-height:inherit;}\n.afm-wrap .afm-faq-body{padding:12px 20px 18px;}\n.afm-wrap .afm-article .afm-faq-body p{margin:0;color:var(--tx) !important;font-size:16px;line-height:1.85;}\n.afm-wrap .afm-cta{background:var(--ob);border:1px solid var(--obd);border-top:4px solid var(--o);border-radius:14px;padding:34px 28px;text-align:center;margin:48px 0 24px;}\n.afm-wrap .afm-article .afm-cta h2{color:var(--hd) !important;border:0;padding:0;font-size:24px;margin:0 0 12px;}\n.afm-wrap .afm-article .afm-cta p{color:var(--tx) !important;font-size:16px;}\n.afm-wrap .afm-article .afm-cta ul{list-style:none;padding:0;margin:14px auto 18px;display:inline-block;text-align:left;}\n.afm-wrap .afm-article .afm-cta li{list-style:none;padding:0 0 0 26px;position:relative;margin:0 0 8px;color:var(--hd) !important;font-size:16px;line-height:1.7;}\n.afm-wrap .afm-article .afm-cta li::before{content:\"\\2713\";position:absolute;left:0;color:var(--o);font-weight:800;}\n.afm-wrap .afm-article a.afm-mail-btn{display:inline-block;background:var(--o);color:#fff !important;text-decoration:none;font-weight:800;font-size:17px;padding:14px 40px;border-radius:999px;margin-top:4px;}\n.afm-wrap .afm-article a.afm-mail-btn:hover{background:var(--od);color:#fff !important;}\n.afm-wrap .afm-article .afm-cta p.afm-cta-sub{margin:18px 0 0;font-size:15px;color:var(--mu) !important;}\n.afm-wrap .afm-brand{border:1px solid var(--line);border-radius:12px;padding:20px;text-align:center;font-size:15px;color:var(--mu) !important;line-height:1.95;background:var(--bg2);margin-top:24px;}\n.afm-wrap .afm-brand strong{color:var(--o) !important;font-size:16px;}\n.afm-wrap .afm-article .afm-brand a{color:var(--od) !important;text-decoration:none;font-weight:600;}\n@media(max-width:768px){.afm-wrap{padding:26px 18px 4px;border-radius:10px;}.afm-wrap .afm-article{font-size:16px;}.afm-wrap .afm-article p{font-size:16px;}.afm-wrap .afm-article h2{font-size:22px;}.afm-wrap .afm-article .afm-toc ul{grid-template-columns:1fr;}.afm-wrap .afm-cta{padding:26px 18px;}.afm-wrap .afm-article a.afm-mail-btn{padding:13px 24px;font-size:16px;}}\n<\/style>\n<div class=\"afm-wrap\">\n<div class=\"afm-progress\" id=\"afmProgress\"><\/div>\n<article class=\"afm-article\">\n<span class=\"afm-guide\">DRAWING GUIDE \u00b7 FORGING TOLERANCES<\/span>\n<div class=\"afm-lead\"><p><strong>A machined forging drawing needs three layers of tolerance. As-forged surfaces follow a forging tolerance standard (EN 586-3 for aluminum in Europe), untoleranced machined dimensions follow the ISO 2768-1 class in the title block, and functional features such as bores, sealing faces, threads and hole positions carry their own size or geometric tolerances.<\/strong> Mixing these layers, or relying on a single \u201cISO 2768-mK\u201d note, is the most common cause of first-article disputes on forged parts.<\/p><\/div>\n<div class=\"afm-tags\"><span class=\"afm-tag\"><a href=\"https:\/\/aft-machining.com\/en\/aluminum-forging-machining-allowance\/\">Machining allowance<\/a><\/span><span class=\"afm-tag\"><a href=\"https:\/\/aft-machining.com\/en\/datum-and-fixture-strategy-for-machining-aluminum-forgings\/\">Datums and fixtures<\/a><\/span><span class=\"afm-tag\">ISO 2768-1<\/span><span class=\"afm-tag\">EN 586-3<\/span><span class=\"afm-tag\">GD&amp;T<\/span><\/div>\n<nav class=\"afm-toc\"><div class=\"afm-toc-t\">IN THIS GUIDE<\/div><ul><li><a href=\"#s1\">I. Three layers of tolerance<\/a><\/li><li><a href=\"#s2\">II. Choosing an ISO 2768-1 class<\/a><\/li><li><a href=\"#s3\">III. ISO 2768-2 vs ISO 22081<\/a><\/li><li><a href=\"#s4\">IV. Standards for as-forged surfaces<\/a><\/li><li><a href=\"#s5\">V. Forged-to-machined dimensions<\/a><\/li><li><a href=\"#s6\">VI. Tolerancing functional features<\/a><\/li><li><a href=\"#s7\">VII. ASME drawings and AFT review<\/a><\/li><li><a href=\"#faq\">FAQ<\/a><\/li><\/ul><\/nav>\n<p>On a forged and machined part, the forge shop reads the forging drawing, the machine shop reads the machining drawing and quality reads the inspection report. When each side interprets untoleranced dimensions differently, the disagreement surfaces at first article inspection. Al Forge Tech (AFT) is an aluminum forging and CNC machining manufacturer in Nantou, Taiwan, and one engineering team reviews both drawings side by side during <a href=\"https:\/\/aft-machining.com\/en\/technology-assessment-and-feasibility-analysis\/\">technical feasibility assessment<\/a>. This guide explains how to layer tolerances for machined forgings, which standards apply where, and what buyers and SQEs can check before sending an RFQ.<\/p>\n<section id=\"s1\">\n<h2><span class=\"afm-rn\">I<\/span>Why do tolerances for machined forgings need three layers?<\/h2>\n<div class=\"afm-answer\">Forged surfaces, machined surfaces and functional features are produced differently, so they need different tolerance rules. ISO 2768-1 covers dimensions produced by metal removal or sheet-metal forming; it was not written for surfaces left as forged.<\/div>\n<p><a href=\"https:\/\/www.iso.org\/standard\/7748.html\" target=\"_blank\" rel=\"noopener\">ISO 2768-1<\/a> applies to dimensions created by cutting or by forming sheet metal. An as-forged surface varies with die wear, mismatch, die-closure thickness and thermal shrinkage, which is a different order of variation from machining. Those surfaces should reference a forging tolerance standard or tolerances agreed on the forging drawing.<\/p>\n<p>In practice, give each part two drawings. The forging drawing defines the blank: parting line, draft, mismatch and flash limits. The machining drawing defines machined surfaces, the datum reference frame and finished tolerances. Both drawings should share one datum scheme, and the gap between them is the machining allowance. See <a href=\"https:\/\/aft-machining.com\/en\/aluminum-forging-machining-allowance\/\">how to size machining allowance on an aluminum forging<\/a> for the calculation.<\/p>\n<div class=\"afm-cards\"><div class=\"afm-card\"><div class=\"afm-num\">1<\/div><div class=\"afm-card-b\"><div class=\"afm-card-t\">Layer 1: as-forged surfaces<\/div><p>Use a forging tolerance standard, typically EN 586-3 for aluminum. These tolerances apply only to dimensions shown on the agreed forging drawing, which becomes the acceptance document.<\/p><\/div><\/div><div class=\"afm-card\"><div class=\"afm-num\">2<\/div><div class=\"afm-card-b\"><div class=\"afm-card-t\">Layer 2: general tolerances on machined surfaces<\/div><p>Machined dimensions without an individual tolerance follow the ISO 2768-1 class stated in the title block; class m suits most parts.<\/p><\/div><\/div><div class=\"afm-card\"><div class=\"afm-num\">3<\/div><div class=\"afm-card-b\"><div class=\"afm-card-t\">Layer 3: functional features<\/div><p>Bores, sealing faces, threads and hole positions get individual size tolerances, fit classes or geometric tolerances tied to a datum reference frame.<\/p><\/div><\/div><\/div>\n<\/section>\n<section id=\"s2\">\n<h2><span class=\"afm-rn\">II<\/span>How do ISO 2768-1 general tolerances work, and when should you choose fine over medium?<\/h2>\n<div class=\"afm-answer\">ISO 2768-1 defines four general tolerance classes: f (fine), m (medium), c (coarse) and v (very coarse). One note in the title block applies the class to every linear and angular dimension without an individual tolerance. Class m covers most CNC-machined features; tighten only the dimensions that need it.<\/div>\n<p>ISO 2768-1:1989 remains the current edition; ISO last reviewed and confirmed it in 2022. The drawing note is simply \u201cISO 2768-m\u201d in or near the title block. The table lists permissible deviations for linear dimensions.<\/p>\n<div class=\"afm-table-wrap\"><table class=\"afm-table\"><thead><tr><th>Nominal size (mm)<\/th><th>f fine<\/th><th>m medium<\/th><th>c coarse<\/th><th>v very coarse<\/th><\/tr><\/thead><tbody><tr><td>0.5\u20133<\/td><td>\u00b10.05<\/td><td>\u00b10.1<\/td><td>\u00b10.2<\/td><td>\u2014<\/td><\/tr><tr><td>3\u20136<\/td><td>\u00b10.05<\/td><td>\u00b10.1<\/td><td>\u00b10.3<\/td><td>\u00b10.5<\/td><\/tr><tr><td>6\u201330<\/td><td>\u00b10.1<\/td><td>\u00b10.2<\/td><td>\u00b10.5<\/td><td>\u00b11.0<\/td><\/tr><tr><td>30\u2013120<\/td><td>\u00b10.15<\/td><td>\u00b10.3<\/td><td>\u00b10.8<\/td><td>\u00b11.5<\/td><\/tr><tr><td>120\u2013400<\/td><td>\u00b10.2<\/td><td>\u00b10.5<\/td><td>\u00b11.2<\/td><td>\u00b12.5<\/td><\/tr><tr><td>400\u20131000<\/td><td>\u00b10.3<\/td><td>\u00b10.8<\/td><td>\u00b12.0<\/td><td>\u00b14.0<\/td><\/tr><tr><td>1000\u20132000<\/td><td>\u00b10.5<\/td><td>\u00b11.2<\/td><td>\u00b13.0<\/td><td>\u00b16.0<\/td><\/tr><\/tbody><\/table><\/div>\n<p class=\"afm-source\">Source: ISO 2768-1:1989, general tolerances for linear dimensions. Ranges are over the lower value up to and including the upper value; values in mm.<\/p>\n<p>Class f is not a quality upgrade. Once the title block says f, every untoleranced machined dimension must be cut and inspected to the fine class, which adds cycle time and inspection cost. A better practice is to keep class m in the title block and call out the dimensions that actually affect fit and function (see section VI).<\/p>\n<p>Some online calculators label class v as suitable for forgings. That is misleading: class v is still an ISO 2768-1 class for machined and sheet-metal dimensions. As-forged surfaces belong under a forging tolerance standard.<\/p>\n<\/section>\n<section id=\"s3\">\n<h2><span class=\"afm-rn\">III<\/span>ISO 2768-2 has been replaced by ISO 22081. Is \u201cISO 2768-mK\u201d still valid?<\/h2>\n<div class=\"afm-answer\">ISO 2768-2:1989, which defined the H, K and L general geometric tolerance classes, has been withdrawn and replaced by ISO 22081:2021. ISO 2768-1 is still current. \u201cISO 2768-mK\u201d remains common on legacy drawings, but new or revised drawings should state which geometric rules apply and confirm them with the supplier.<\/div>\n<p><a href=\"https:\/\/www.iso.org\/standard\/72514.html\" target=\"_blank\" rel=\"noopener\">ISO 22081:2021<\/a> was developed by ISO\/TC 213 as a geometrical product specification (GPS) standard. It provides tools for general geometrical specifications and general size specifications, clarifies the rules for applying them, and is written differently from the old H, K and L classes. ISO confirmed the standard after its review in June 2026.<\/p>\n<p>For buyers and SQEs, the goal is not chasing the newest edition. It is making sure both parties read the drawing the same way. A practical approach by drawing status:<\/p>\n<ul class=\"afm-checks\"><li><strong>Legacy production drawings:<\/strong> if the title block says ISO 2768-mK, agree with the supplier before first article how untoleranced flatness, perpendicularity and similar requirements will be judged.<\/li><li><strong>New or revised drawings:<\/strong> keep ISO 2768-1 for general size tolerances, and either adopt ISO 22081 for general geometry or call out important form and location requirements individually.<\/li><li><strong>No general geometric tolerances on as-forged surfaces:<\/strong> flatness or straightness of forged surfaces should follow the forging tolerance standard or values agreed on the forging drawing.<\/li><\/ul>\n<\/section>\n<section id=\"s4\">\n<h2><span class=\"afm-rn\">IV<\/span>Which standard covers tolerances on as-forged surfaces?<\/h2>\n<div class=\"afm-answer\">In Europe, as-forged dimensions and form on aluminum forgings usually follow EN 586-3; steel die forgings typically follow EN 10243-1. These tolerances generally apply only to dimensions shown on the agreed forging drawing, so that drawing is the acceptance document for unmachined surfaces.<\/div>\n<p><a href=\"https:\/\/webstore.ansi.org\/standards\/din\/dinen5862002\" target=\"_blank\" rel=\"noopener\">EN 586-3<\/a> specifies dimensional and form tolerances for hot-formed aluminum and aluminum alloy forgings. Its scope covers die forgings that are not machined all over up to 2,000 mm shape dimension, 600 mm die-closure dimension and 4,000 cm\u00b2 projected area, and die forgings machined all over up to 6,000 mm and 22,000 cm\u00b2. Larger or complex forgings use tolerances agreed between supplier and purchaser.<\/p>\n<p>A forging drawing needs more than length, width and height. Draft, mismatch, residual flash, ejector marks, fillet radii and die-closure dimensions all affect how the part is located and how much stock is left for machining. Most U.S. drawings do not cite EN 586-3; ASM International\u2019s chapter on <a href=\"https:\/\/dl.asminternational.org\/handbooks\/book\/31\/chapter\/431036\/Forging-Design-Dimensions-and-Tolerances\" target=\"_blank\" rel=\"noopener\">forging design dimensions and tolerances<\/a> and the Forging Industry Association\u2019s <a href=\"https:\/\/www.forging.org\/Common\/Uploaded%20files\/Design%20Engineering%20Center\/Product%20Design%20Guide%20for%20Forging.pdf\" target=\"_blank\" rel=\"noopener\">Product Design Guide for Forging<\/a> are common references, with agreed values written directly on the forging drawing.<\/p>\n<p>Forging geometry and parting-line design also decide which surfaces can stay as forged. For design guidance from the forging side, see AFT\u2019s <a href=\"https:\/\/aft-forge.com\/en\/blog\/aluminum-forging-dfm-balancing-aesthetics-and-function-in-scalable-product-design\/\" target=\"_blank\" rel=\"noopener\">aluminum forging DFM guide<\/a>.<\/p>\n<\/section>\n<section id=\"s5\">\n<h2><span class=\"afm-rn\">V<\/span>What tolerance applies to a dimension between a forged surface and a machined surface?<\/h2>\n<div class=\"afm-answer\">If a dimension runs from a forged surface to a machined surface and has no individual tolerance, ISO 2768-1 applies the larger of the two general tolerances. The safer practice is to dimension such features from machined datums and state the allowed range directly on the machining drawing.<\/div>\n<p>Take a boss height measured from a machined mounting face to an unmachined forged top. The dimension carries both forging and machining variation. If the drawing only says ISO 2768-m, the machine shop may assume class m applies, while the forged surface alone can vary by more than that. Three habits prevent the argument:<\/p>\n<ul class=\"afm-checks\"><li><strong>Dimension from machined datums:<\/strong> locate unmachined features from the datum face and datum holes created in the first operation, not by chaining from another forged surface. See <a href=\"https:\/\/aft-machining.com\/en\/datum-and-fixture-strategy-for-machining-aluminum-forgings\/\">datum and fixture strategy for machining aluminum forgings<\/a>.<\/li><li><strong>State the range:<\/strong> where a forged dimension affects assembly, give it an individual tolerance on the machining drawing instead of relying on the larger-of-two rule.<\/li><li><strong>Specify minimum wall:<\/strong> where a machined feature approaches a forged surface, a minimum wall or minimum remaining thickness protects strength better than a nominal dimension.<\/li><\/ul>\n<\/section>\n<section id=\"s6\">\n<h2><span class=\"afm-rn\">VI<\/span>How should bores, sealing faces, threads and hole positions be toleranced?<\/h2>\n<div class=\"afm-answer\">Any feature that affects fit, sealing or load path needs its own size or geometric tolerance and a defined datum for inspection. General tolerances should only cover dimensions where \u201cclose enough\u201d is acceptable. The table summarizes typical callouts on machined aluminum forgings.<\/div>\n<div class=\"afm-table-wrap\"><table class=\"afm-table\"><thead><tr><th>Feature<\/th><th>Recommended callout<\/th><th>Reference<\/th><th>Typical inspection<\/th><th>Common mistake<\/th><\/tr><\/thead><tbody><tr><td>As-forged surface<\/td><td>Dimension and forging tolerance on the forging drawing<\/td><td>EN 586-3 or agreed values<\/td><td>3D scan comparison, gauges<\/td><td>Applying ISO 2768 on the machining drawing<\/td><\/tr><tr><td>General machined surface<\/td><td>ISO 2768-m in the title block<\/td><td>ISO 2768-1<\/td><td>Calipers, height gauge, CMM<\/td><td>Calling class f for the whole drawing<\/td><\/tr><tr><td>Bearing or fit bore<\/td><td>Tolerance class (e.g. H7) plus cylindricity<\/td><td>ISO 286<\/td><td>Plug gauge, bore gauge, CMM<\/td><td>Nominal size only<\/td><\/tr><tr><td>Sealing face<\/td><td>Flatness plus surface roughness<\/td><td>ISO 1101, roughness spec<\/td><td>CMM, roughness tester<\/td><td>Roughness without flatness<\/td><\/tr><tr><td>Thread<\/td><td>Thread size and class (e.g. M8\u00d71.25-6H)<\/td><td>ISO 965<\/td><td>Go\/no-go gauges<\/td><td>No before\/after anodize note<\/td><\/tr><tr><td>Hole pattern<\/td><td>Position tolerance to a datum reference frame<\/td><td>ISO 1101 or ASME Y14.5<\/td><td>CMM<\/td><td>\u00b1 coordinate tolerances with no datums<\/td><\/tr><tr><td>Parting line and flash<\/td><td>Location and residual flash on the forging drawing<\/td><td>Agreed on forging drawing<\/td><td>Visual, gauges<\/td><td>Parting line on a sealing or cosmetic face<\/td><\/tr><\/tbody><\/table><\/div>\n<p class=\"afm-source\">Sources: ISO 2768-1, ISO 22081, EN 586-3, ASME Y14.5; AFT machining practice. Actual tolerances depend on the drawing and functional requirements.<\/p>\n<p>For anodized or hardcoated parts, also state whether dimensions apply before or after finishing. Coating buildup and thread treatment are covered in <a href=\"https:\/\/aft-machining.com\/en\/anodizing-and-hardcoat-machining-allowance-aluminum-forgings\/\">designing machined aluminum forgings for anodizing and hardcoat<\/a>.<\/p>\n<\/section>\n<section id=\"s7\">\n<h2><span class=\"afm-rn\">VII<\/span>What changes on ASME Y14.5 drawings, and how does AFT review them?<\/h2>\n<div class=\"afm-answer\">Most U.S. drawings follow ASME Y14.5, which does not define general tolerance classes like ISO 2768; untoleranced dimensions are usually governed by title-block tolerances based on decimal places. If a program mixes ISO and ASME drawings, agree on one set of acceptance rules before sampling.<\/div>\n<p>There is a second difference that is easy to miss. <a href=\"https:\/\/www.asme.org\/codes-standards\/find-codes-standards\/y14-5-dimensioning-tolerancing\/2018\" target=\"_blank\" rel=\"noopener\">ASME Y14.5<\/a> applies the envelope principle by default (Rule #1), so a size tolerance also limits form. ISO drawings follow the independency principle of ISO 8015 by default, judging size and form separately unless the envelope requirement is indicated. The same bore can pass under one system and fail under the other.<\/p>\n<p>When AFT receives an RFQ, the engineering team reviews the forging and machining drawings together: which surfaces are machined and which stay as forged, whether both drawings share one datum scheme, whether the title-block general tolerances suit a forging, and whether every functional feature has its own tolerance. Questions are raised before quoting, not discovered at first article.<\/p>\n<p>On the inspection side, AFT measures machined dimensions on four Zeiss CMMs aligned to the machining datums, checks forged contours with a handheld 3D scanner, and uses a contour tracer and surface roughness tester for profiles and sealing faces. Records are kept under IATF 16949:2016; see <a href=\"https:\/\/aft-machining.com\/en\/manufacturing-and-quality-control\/\">manufacturing and quality control<\/a> for the full flow.<\/p>\n<div class=\"afm-callout\"><p><strong>Drawing checklist before you send an RFQ:<\/strong><\/p><p>1. Are there separate forging and machining drawings that share one datum scheme?<\/p><p>2. Does the machining drawing show clearly which surfaces are machined and which stay as forged?<\/p><p>3. Does the title block state the general tolerance standard and class (e.g. ISO 2768-m), and whether geometry follows ISO 2768-2, ISO 22081 or individual callouts?<\/p><p>4. Do as-forged surfaces reference EN 586-3 or another forging tolerance standard, or tolerances agreed on the forging drawing?<\/p><p>5. Do bores, sealing faces, threads and hole patterns all have individual tolerances and inspection datums?<\/p><p>6. For anodized or coated parts, are dimensions marked as before or after finishing?<\/p><\/div>\n<\/section>\n<section id=\"faq\" class=\"afm-faq\"><h2>FAQ<\/h2>\n<details><summary><h3>Can a forging drawing just say ISO 2768-m?<\/h3><\/summary><div class=\"afm-faq-body\"><p>It is not recommended. ISO 2768-1 covers dimensions produced by machining or sheet-metal forming, not surfaces left as forged. A forged part should also reference a forging tolerance standard, such as EN 586-3 for aluminum, or carry tolerances agreed on the forging drawing.<\/p><\/div><\/details>\n<details><summary><h3>Which tolerance applies between a forged surface and a machined surface?<\/h3><\/summary><div class=\"afm-faq-body\"><p>Without an individual tolerance, ISO 2768-1 applies the larger of the two general tolerances. Because these dimensions often cause disputes, dimension them from machined datums and state the allowed range on the machining drawing.<\/p><\/div><\/details>\n<details><summary><h3>What does ISO 2768-mK mean, and is it still valid?<\/h3><\/summary><div class=\"afm-faq-body\"><p>The m is the medium linear tolerance class of ISO 2768-1, and the K is a general geometric tolerance class from ISO 2768-2. ISO 2768-2 was replaced by ISO 22081 in 2021, yet mK still appears on many drawings, so confirm with your supplier how geometric requirements will be judged.<\/p><\/div><\/details>\n<details><summary><h3>Which dimensions should never rely on general tolerances?<\/h3><\/summary><div class=\"afm-faq-body\"><p>Dimensions that affect fit, sealing or load, such as bearing bores, fit bores, sealing faces, threads and hole positions, need individual size tolerances, fit classes or geometric tolerances. General tolerances suit only dimensions that do not affect function.<\/p><\/div><\/details>\n<details><summary><h3>How do forging tolerances compare with CNC machining tolerances?<\/h3><\/summary><div class=\"afm-faq-body\"><p>They operate on different scales, and actual values depend on part size, forging type and machining method. Forging tolerances include die wear, mismatch and die-closure variation, so they are usually wider; surfaces that need precision should carry machining stock and be finished by CNC. Send your drawing and our engineers will assess the specific values.<\/p><\/div><\/details>\n<details><summary><h3>What does a supplier do if a drawing has no tolerances?<\/h3><\/summary><div class=\"afm-faq-body\"><p>A responsible supplier raises the question before quoting and asks you to add tolerances or confirm the acceptance basis. Producing without clarification often leads to disputes at first article inspection, so state your general and geometric tolerance standards when you send the drawing.<\/p><\/div><\/details>\n<\/section>\n<div class=\"afm-cta\"><h2>Have our engineers check your tolerancing before you quote<\/h2>\n<p>AFT can review your forging and machining drawings together, confirm which surfaces stay as forged, check that both drawings share one datum scheme, and flag dimensions that need an individual tolerance or could be relaxed. Our engineers will reply with an initial feasibility view and list anything still needed. If you need an NDA before sharing drawings, just ask.<\/p>\n<p>Please send:<\/p>\n<ul><li>2D machining drawing with title-block general and geometric tolerances<\/li><li>Forging drawing or blank dimensions, if available<\/li><li>3D model in STEP or IGES<\/li><li>Alloy, temper and surface finish requirements<\/li><\/ul><br>\n<a class=\"afm-mail-btn\" href=\"mailto:aft@aft-forge.com.tw\">Email aft@aft-forge.com.tw<\/a>\n<p class=\"afm-cta-sub\">Or send your details through our <a href=\"https:\/\/aft-machining.com\/en\/contactus\/\">Contact Us page<\/a><\/p>\n<\/div>\n<div class=\"afm-brand\"><strong>AFT | Al Forge Tech<\/strong> | Nantou, Taiwan \u00b7 Aluminum forging, T4\/T6 heat treatment and CNC machining under one roof<br>Browse: <a href=\"https:\/\/aft-machining.com\/en\/aluminum-forging-machining\/\">Forging &amp; machining overview<\/a> | <a href=\"https:\/\/aft-machining.com\/en\/aluminum-forging-machining-equipment\/\">Machining equipment<\/a> | <a href=\"https:\/\/aft-machining.com\/en\/solution\/\">Custom solutions<\/a> | <a href=\"https:\/\/aft-forge.com\/en\/\" target=\"_blank\" rel=\"noopener\">AFT forging website<\/a><\/div>\n<\/article><\/div>\n<script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"FAQPage\",\n  \"mainEntity\": [\n    {\n      \"@type\": \"Question\",\n      \"name\": \"Can a forging drawing just say ISO 2768-m?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"It is not recommended. 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Because these dimensions often cause disputes, dimension them from machined datums and state the allowed range on the machining drawing.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What does ISO 2768-mK mean, and is it still valid?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"The m is the medium linear tolerance class of ISO 2768-1, and the K is a general geometric tolerance class from ISO 2768-2. 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Producing without clarification often leads to disputes at first article inspection, so state your general and geometric tolerance standards when you send the drawing.\"\n      }\n    }\n  ]\n}\n<\/script>\n<script>\n(function(){var bar=document.getElementById('afmProgress');if(!bar)return;window.addEventListener('scroll',function(){var h=document.documentElement;var max=h.scrollHeight-h.clientHeight;bar.style.width=(max>0?(h.scrollTop\/max)*100:0)+'%';},{passive:true});})();\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>DRAWING GUIDE \u00b7 FORGING TOLERANCES A machined forging d [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[19],"tags":[],"class_list":["post-3673","post","type-post","status-publish","format-standard","hentry","category-blog"],"acf":[],"_links":{"self":[{"href":"https:\/\/aft-machining.com\/en\/wp-json\/wp\/v2\/posts\/3673","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/aft-machining.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/aft-machining.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/aft-machining.com\/en\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/aft-machining.com\/en\/wp-json\/wp\/v2\/comments?post=3673"}],"version-history":[{"count":1,"href":"https:\/\/aft-machining.com\/en\/wp-json\/wp\/v2\/posts\/3673\/revisions"}],"predecessor-version":[{"id":3674,"href":"https:\/\/aft-machining.com\/en\/wp-json\/wp\/v2\/posts\/3673\/revisions\/3674"}],"wp:attachment":[{"href":"https:\/\/aft-machining.com\/en\/wp-json\/wp\/v2\/media?parent=3673"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aft-machining.com\/en\/wp-json\/wp\/v2\/categories?post=3673"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aft-machining.com\/en\/wp-json\/wp\/v2\/tags?post=3673"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}