{"id":2274,"date":"2026-09-15T09:32:11","date_gmt":"2026-09-15T01:32:11","guid":{"rendered":"https:\/\/www.jccncmachining.com\/?p=2274"},"modified":"2026-09-12T09:24:13","modified_gmt":"2026-09-12T01:24:13","slug":"iso-2768-on-cnc-drawings-where-general-tolerances-stop","status":"publish","type":"post","link":"https:\/\/www.jccncmachining.com\/it\/blog\/iso-2768-on-cnc-drawings-where-general-tolerances-stop\/","title":{"rendered":"ISO 2768 on CNC Drawings: Where General Tolerances Stop"},"content":{"rendered":"<article class=\"blog-post\">\n<p class=\"lead\" style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\"><strong>ISO 2768 for CNC machining drawings<\/strong> is a way to assign general tolerances to dimensions that do not have individual limits. It can make a drawing easier to read, but it does not replace functional fits, GD&amp;T, material definition, surface finish, or a supplier&#8217;s project-specific review. The useful question is not whether ISO 2768 appears in the title block; it is whether the selected class matches the non-critical dimensions and leaves critical features explicitly controlled.<\/p>\n<section class=\"key-takeaways\">\n<h2 style=\"font-size: 26px; line-height: 1.25; margin-top: 46.8px; margin-bottom: 18.2px;\">What ISO 2768 Can-and Cannot-Do<\/h2>\n<p><img decoding=\"async\" width=\"1024\" height=\"576\" loading=\"lazy\" src=\"https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-1-3-1024x576.webp\" alt=\"General tolerance review\" class=\"size-large wp-image-2309 aligncenter\" \/>\n<ul style=\"font-size: 15px; line-height: 1.82;\" srcset=\"https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-1-3-1024x576.webp 1024w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-1-3-300x169.webp 300w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-1-3-768x432.webp 768w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-1-3-1536x864.webp 1536w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-1-3-18x10.webp 18w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-1-3-800x450.webp 800w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-1-3.webp 1600w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/>\n<li>It provides a general framework for unspecified linear, angular, and geometric dimensions.<\/li>\n<li>It does not automatically define bearing fits, hole patterns, sealing faces, threads, or assembly-critical relationships.<\/li>\n<li>The drawing must state the applicable class and units clearly.<\/li>\n<li>Critical dimensions should override the general note with their own requirement.<\/li>\n<\/ul>\n<\/section>\n<nav class=\"table-of-contents\" aria-label=\"Table of contents\">\n<h2 style=\"font-size: 26px; line-height: 1.25; margin-top: 46.8px; margin-bottom: 18.2px;\">Reading the Drawing Note<\/h2>\n<ol style=\"font-size: 15px; line-height: 1.82;\">\n<li><a href=\"#scope\">Understand the scope<\/a><\/li>\n<li><a href=\"#class\">Select a practical class<\/a><\/li>\n<li><a href=\"#exceptions\">Separate exceptions from defaults<\/a><\/li>\n<li><a href=\"#features\">Protect critical features<\/a><\/li>\n<li><a href=\"#supplier\">Prepare the supplier review<\/a><\/li>\n<li><a href=\"#faq\">ISO 2768 FAQs<\/a><\/li>\n<\/ol>\n<\/nav>\n<section id=\"scope\">\n<h2 style=\"font-size: 26px; line-height: 1.25; margin-top: 46.8px; margin-bottom: 18.2px;\">Understand the scope<\/h2>\n<p><img decoding=\"async\" width=\"1024\" height=\"576\" loading=\"lazy\" src=\"https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-2-3-1024x576.webp\" alt=\"Tolerance scope review\" class=\"size-large wp-image-2304 aligncenter\" \/>\n<p style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\" srcset=\"https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-2-3-1024x576.webp 1024w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-2-3-300x169.webp 300w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-2-3-768x432.webp 768w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-2-3-1536x864.webp 1536w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-2-3-18x10.webp 18w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-2-3-800x450.webp 800w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-2-3.webp 1600w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/>A general tolerance note applies only where the drawing does not provide a more specific requirement. It should be read together with the drawing&#8217;s units, decimal conventions, title-block notes, material callout, finish, and any geometric controls. A 3D model alone cannot reveal those defaults reliably.<\/p>\n<p style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\">The selected ISO 2768 designation also has a defined scope. Do not assume that one general note controls every geometric characteristic or every feature in the same way. If a feature affects fit, sealing, motion, alignment, or safety, identify the requirement directly.<\/p>\n<\/section>\n<section id=\"class\">\n<h2 style=\"font-size: 26px; line-height: 1.25; margin-top: 46.8px; margin-bottom: 18.2px;\">Select a practical class<\/h2>\n<p><img decoding=\"async\" width=\"1024\" height=\"576\" loading=\"lazy\" src=\"https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-3-3-1024x576.webp\" alt=\"CNC tolerance class comparison\" class=\"size-large wp-image-2305 aligncenter\" \/>\n<p style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\" srcset=\"https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-3-3-1024x576.webp 1024w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-3-3-300x169.webp 300w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-3-3-768x432.webp 768w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-3-3-1536x864.webp 1536w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-3-3-18x10.webp 18w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-3-3-800x450.webp 800w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-3-3.webp 1600w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/>A finer class may reduce variation on ordinary dimensions, but it can also add machining, inspection, and quotation risk. A coarser class may be suitable for clearance geometry or nonfunctional outside features. The class should follow the product function and process capability, not a blanket preference for &#8220;precision.&#8221;<\/p>\n<table style=\"width: 100%; border-collapse: collapse; font-size: 15px; line-height: 1.82; margin: 24px 0;\">\n<thead>\n<tr>\n<th style=\"border: 1px solid #ccc; padding: 10px; text-align: left;\">Feature role<\/th>\n<th style=\"border: 1px solid #ccc; padding: 10px; text-align: left;\">General-note approach<\/th>\n<th style=\"border: 1px solid #ccc; padding: 10px; text-align: left;\">Better drawing action<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"border: 1px solid #ccc; padding: 10px;\">Non-critical edge<\/td>\n<td style=\"border: 1px solid #ccc; padding: 10px;\">General tolerance may be adequate<\/td>\n<td style=\"border: 1px solid #ccc; padding: 10px;\">Confirm it cannot affect assembly or safety<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #ccc; padding: 10px;\">Bearing or locating feature<\/td>\n<td style=\"border: 1px solid #ccc; padding: 10px;\">Do not rely on the default alone<\/td>\n<td style=\"border: 1px solid #ccc; padding: 10px;\">Specify size, fit, datum, form, and surface condition<\/td>\n<\/tr>\n<tr>\n<td style=\"border: 1px solid #ccc; padding: 10px;\">Cosmetic profile<\/td>\n<td style=\"border: 1px solid #ccc; padding: 10px;\">General note may not describe appearance<\/td>\n<td style=\"border: 1px solid #ccc; padding: 10px;\">Add profile, edge, and visual acceptance criteria<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/section>\n<section id=\"exceptions\">\n<h2 style=\"font-size: 26px; line-height: 1.25; margin-top: 46.8px; margin-bottom: 18.2px;\">Separate exceptions from defaults<\/h2>\n<p style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\">The drawing should make exceptions easy to find. Use individual limits for holes, shafts, slots, threads, sealing surfaces, critical thicknesses, and mating faces. Use GD&amp;T when the risk concerns position, orientation, form, or profile rather than size alone. This prevents a supplier and inspector from applying a general note to the wrong feature.<\/p>\n<p style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\">For a wider explanation of how functional requirements should be separated from general dimensions, see the site&#8217;s <a href=\"https:\/\/www.jccncmachining.com\/it\/blog\/cnc-machining-tolerances\/\">CNC machining tolerances guide<\/a>.<\/p>\n<\/section>\n<section id=\"features\">\n<h2 style=\"font-size: 26px; line-height: 1.25; margin-top: 46.8px; margin-bottom: 18.2px;\">Protect critical features<\/h2>\n<p><img decoding=\"async\" width=\"1024\" height=\"576\" loading=\"lazy\" src=\"https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-4-3-1024x576.webp\" alt=\"Critical feature inspection\" class=\"size-large wp-image-2306 aligncenter\" \/>\n<p style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\" srcset=\"https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-4-3-1024x576.webp 1024w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-4-3-300x169.webp 300w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-4-3-768x432.webp 768w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-4-3-1536x864.webp 1536w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-4-3-18x10.webp 18w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-4-3-800x450.webp 800w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-4-3.webp 1600w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/>ISO 2768 does not tell a supplier how a coated bore should be measured, which datum controls a hole pattern, or whether a flat face must remain suitable for sealing. Those are project requirements. Include final surface state, material condition, edge treatment, inspection timing, and any functional test when they affect acceptance.<\/p>\n<ol style=\"font-size: 15px; line-height: 1.82;\">\n<li>Highlight features that locate, seal, rotate, slide, or carry load.<\/li>\n<li>Define the final condition after heat treatment, plating, anodizing, or polishing.<\/li>\n<li>Link position and orientation controls to a usable datum reference frame.<\/li>\n<li>State whether the supplier should provide a dimensional, CMM, or functional report.<\/li>\n<\/ol>\n<\/section>\n<section id=\"supplier\">\n<h2 style=\"font-size: 26px; line-height: 1.25; margin-top: 46.8px; margin-bottom: 18.2px;\">Prepare the supplier review<\/h2>\n<p><img decoding=\"async\" width=\"1024\" height=\"576\" loading=\"lazy\" src=\"https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-5-3-1024x576.webp\" alt=\"Supplier drawing review\" class=\"size-large wp-image-2307 aligncenter\" \/>\n<p style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\" srcset=\"https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-5-3-1024x576.webp 1024w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-5-3-300x169.webp 300w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-5-3-768x432.webp 768w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-5-3-1536x864.webp 1536w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-5-3-18x10.webp 18w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-5-3-800x450.webp 800w, https:\/\/www.jccncmachining.com\/wp-content\/uploads\/2026\/09\/h2-5-3.webp 1600w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/>Before an RFQ, check the title block, revision, units, general tolerance note, material grade, finish, critical callouts, and inspection requirements as one package. Ask the supplier to flag a general tolerance that is tighter than the function requires or a feature whose requirement cannot be reproduced by the proposed inspection method. Process context is available on the site&#8217;s <a href=\"https:\/\/www.jccncmachining.com\/it\/capabilities\/\">CNC machining capabilities<\/a> page, but the controlled drawing remains the acceptance reference.<\/p>\n<\/section>\n<section id=\"faq\">\n<h2 style=\"font-size: 26px; line-height: 1.25; margin-top: 46.8px; margin-bottom: 18.2px;\">ISO 2768 FAQs<\/h2>\n<h3 style=\"font-size: 20px; line-height: 1.25; margin-top: 36px; margin-bottom: 14px;\">Does ISO 2768 apply to every CNC dimension?<\/h3>\n<p style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\">It applies only within the scope stated by the drawing and only where no more specific requirement overrides it. Critical features should have their own limits or geometric controls.<\/p>\n<h3 style=\"font-size: 20px; line-height: 1.25; margin-top: 36px; margin-bottom: 14px;\">Can ISO 2768 replace GD&amp;T?<\/h3>\n<p style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\">No. A general dimensional tolerance does not fully describe position, orientation, form, or profile relationships that may control assembly.<\/p>\n<h3 style=\"font-size: 20px; line-height: 1.25; margin-top: 36px; margin-bottom: 14px;\">Should a bearing bore use only a general tolerance?<\/h3>\n<p style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\">Usually not. Define the fit, size limits, axis relationship, surface condition, datum, and final inspection state according to the bearing and housing function.<\/p>\n<h3 style=\"font-size: 20px; line-height: 1.25; margin-top: 36px; margin-bottom: 14px;\">What is the risk of choosing a very fine class?<\/h3>\n<p style=\"font-size: 15px; line-height: 1.82; margin-bottom: 16.5px; text-align: left;\">It may increase machining and inspection effort for features that do not benefit from the tighter default. Apply precision where the product needs it.<\/p>\n<\/section>\n<\/article>","protected":false},"excerpt":{"rendered":"<p>ISO 2768 for CNC machining drawings is a way to assign general tolerances to dimensions that do not have individual limits. It can make a drawing easier to read, but it does not replace functional fits, GD&amp;T, material definition, surface finish, or a supplier&#8217;s project-specific review. The useful question is not whether ISO 2768 appears [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":2308,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-2274","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"_links":{"self":[{"href":"https:\/\/www.jccncmachining.com\/it\/wp-json\/wp\/v2\/posts\/2274","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.jccncmachining.com\/it\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.jccncmachining.com\/it\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.jccncmachining.com\/it\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.jccncmachining.com\/it\/wp-json\/wp\/v2\/comments?post=2274"}],"version-history":[{"count":9,"href":"https:\/\/www.jccncmachining.com\/it\/wp-json\/wp\/v2\/posts\/2274\/revisions"}],"predecessor-version":[{"id":2310,"href":"https:\/\/www.jccncmachining.com\/it\/wp-json\/wp\/v2\/posts\/2274\/revisions\/2310"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.jccncmachining.com\/it\/wp-json\/wp\/v2\/media\/2308"}],"wp:attachment":[{"href":"https:\/\/www.jccncmachining.com\/it\/wp-json\/wp\/v2\/media?parent=2274"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.jccncmachining.com\/it\/wp-json\/wp\/v2\/categories?post=2274"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.jccncmachining.com\/it\/wp-json\/wp\/v2\/tags?post=2274"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}