{"id":2904,"date":"2026-07-19T06:07:29","date_gmt":"2026-07-18T22:07:29","guid":{"rendered":"https:\/\/bravofabs.com\/sheet-metal-design-guide\/"},"modified":"2026-09-10T13:08:49","modified_gmt":"2026-09-10T05:08:49","slug":"sheet-metal-design-guide","status":"publish","type":"post","link":"https:\/\/bravofabs.com\/sheet-metal-design-guide\/","title":{"rendered":"Sheet Metal Design Guide: Bend Radius, K-Factor &#038; Hole Spacing"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">Key Takeaways<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Inside bend radius \u2265 1\u00d7 material thickness<\/strong> is the rule that prevents cracked bends \u2014 aluminum 5052 wants 1\u20131.5\u00d7, annealed stainless 1\u20132\u00d7, and harder tempers need more.<\/li>\n<li><strong>K-factor (typically 0.3\u20130.5, commonly 0.33\u20130.44)<\/strong> locates the neutral axis and drives your flat-pattern math: BA = (\u03c0 \u00d7 angle\/180) \u00d7 (R + K \u00d7 t). Get it wrong and every flange lands short or long.<\/li>\n<li><strong>Keep holes at least 2.5\u00d7 thickness + bend radius away from bend lines<\/strong> \u2014 closer than that, they stretch into ovals. Slots need 4\u00d7 t + R.<\/li>\n<li><strong>Flanges must be at least 4\u00d7 material thickness tall<\/strong>, or the press brake has nothing to grip and the bend needs costly secondary operations.<\/li>\n<li><strong>Springback is physics, not a defect<\/strong> \u2014 every air bend relaxes a few degrees when released; your fabricator over-bends to compensate, and harder materials spring back more.<\/li>\n<li><strong>One uniform thickness, generous radii, features clear of bends<\/strong> \u2014 parts that follow the rules quote faster, cost less, and never come back with &#8220;can you move this hole?&#8221;<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Most sheet metal parts that get flagged in DFM review fail on the same four points: a bend radius the material can&#8217;t take, holes crowding a bend line, flanges too short to form, and flat patterns that don&#8217;t account for how metal actually stretches. None of these are exotic \u2014 they&#8217;re all covered by rules of thumb every fabricator uses daily.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This <strong>sheet metal design guide<\/strong> collects those rules in one place \u2014 <strong>bend radius<\/strong>, K-factor, hole spacing, flange height, and springback \u2014 with the numbers, the reasons behind them, and a checklist you can run before any drawing goes out for <a href=\"https:\/\/bravofabs.com\/sheet-metal-fabrication-services\/\">sheet metal fabrication<\/a>.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table style=\"width:100%;border-collapse:collapse\"><thead><tr style=\"background:#004c97;color:#fff\"><th>Design Rule<\/th><th>Minimum Guideline<\/th><th>What Happens If Ignored<\/th><\/tr><\/thead><tbody><tr><td><strong>Inside bend radius<\/strong><\/td><td>\u2265 1\u00d7 thickness (1T)<\/td><td>Cracking on the outside of the bend<\/td><\/tr><tr style=\"background:#f4f7fb\"><td><strong>Hole to bend line<\/strong><\/td><td>\u2265 2.5T + bend radius<\/td><td>Holes distort into ovals<\/td><\/tr><tr><td><strong>Slot to bend line<\/strong><\/td><td>\u2265 4T + bend radius<\/td><td>Slot edges pull and warp<\/td><\/tr><tr style=\"background:#f4f7fb\"><td><strong>Flange height<\/strong><\/td><td>\u2265 4T<\/td><td>Too short for press brake tooling to grip<\/td><\/tr><tr><td><strong>Hole diameter<\/strong><\/td><td>\u2265 1T (2T for stainless when punched)<\/td><td>Punch breakage, ragged holes<\/td><\/tr><tr style=\"background:#f4f7fb\"><td><strong>Hole to edge<\/strong><\/td><td>\u2265 2T of web<\/td><td>Material bulges at the edge<\/td><\/tr><tr><td><strong>Bend relief width \/ length<\/strong><\/td><td>\u2265 1T wide, longer than bend radius<\/td><td>Tearing at flange corners<\/td><\/tr><\/tbody><\/table><figcaption class=\"wp-element-caption\">Sheet metal design cheat sheet (T = material thickness). Consolidated from standard fabrication DFM guidelines.<\/figcaption><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">Bend Radius: The Rule That Prevents Cracking<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">When sheet metal bends, the outside surface stretches. Ask it to stretch around too tight a radius and it cracks \u2014 visibly on a bad day, as invisible micro-fissures that fail in service on a worse one. The baseline rule: <strong>keep the inside bend radius at least equal to the material thickness (1T)<\/strong>. A 2 mm sheet gets a 2 mm inside radius, minimum.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Material moves the number. Ductile cold rolled steel handles 1T comfortably. <strong>Aluminum 5052-H32 prefers 1\u20131.5T<\/strong> \u2014 thin gauges tolerate tighter, thick and harder tempers need more \u2014 while 6061-T6 is the classic cracking candidate and wants generous radii or a bend across the rolling grain. <strong>Annealed stainless 304 runs 1\u20132T<\/strong> thanks to work-hardening at the bend. Two habits keep you safe: don&#8217;t design a smaller radius than the material family allows, and where a bend runs near the sheet&#8217;s rolling direction, orient it across the grain when possible. For material-level guidance, pair this article with our <a href=\"https:\/\/bravofabs.com\/sheet-metal-material-selection\/\">sheet metal material selection guide<\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">K-Factor and Bend Allowance: Why Flat Patterns Don&#8217;t Add Up<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Bend a sheet and the outer surface stretches while the inner surface compresses. Somewhere between them lies the <strong>neutral axis<\/strong> \u2014 the layer that keeps its original length. The <strong>K-factor<\/strong> is simply where that layer sits, as a fraction of thickness measured from the inside: K = 0.44 means 44% of the way through. Typical values run <strong>0.3\u20130.5<\/strong>, with 0.33 common for tight air bends and 0.44 the default in most CAD systems.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">K-factor feeds the <strong>bend allowance<\/strong> \u2014 the arc length of material consumed by each bend, which determines your flat-pattern size:<\/p>\n\n\n\n<p class=\"has-background wp-block-paragraph\" style=\"background-color:#f8f9fb;padding-top:10px;padding-right:14px;padding-bottom:10px;padding-left:14px\"><strong>Bend Allowance = (\u03c0 \u00d7 bend angle \/ 180) \u00d7 (R + K \u00d7 t)<\/strong><br>where R = inside bend radius, K = K-factor, t = material thickness. Example: 2 mm steel, 90\u00b0 bend, R = 3 mm, K = 0.44 \u2192 BA = 1.571 \u00d7 (3 + 0.88) \u2248 6.1 mm per bend.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The practical advice: <strong>don&#8217;t fight your fabricator&#8217;s numbers.<\/strong> K-factor varies with material, tooling, and bending method, and every shop calibrates against its own press brakes. Design with your CAD default, send STEP + flat-aware drawings, and let the shop apply its measured bend tables \u2014 flanges then land on dimension. What you must not do is hard-code flat patterns from an uncalibrated K and dimension the blank as gospel.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Hole Spacing and Placement Rules<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Bending pulls material toward the bend. Any feature inside that pull zone deforms with it, which is why hole placement rules exist:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Holes: \u2265 2.5T + R from the bend line.<\/strong> Closer holes stretch oval and threads stop gauging. If function forces a closer hole, cut it after bending \u2014 and expect the cost line to say so.<\/li>\n<li><strong>Slots: \u2265 4T + R from the bend.<\/strong> Long openings surrender more edge to the pull and distort sooner than round holes.<\/li>\n<li><strong>Hole diameter: \u2265 1T<\/strong> for laser-cut features, and \u2265 2T when punching stainless or high-tensile sheet \u2014 small punches in hard material break.<\/li>\n<li><strong>Hole to edge: \u2265 2T of web<\/strong>, or the edge bulges when the hole is cut or the part is formed.<\/li>\n<li><strong>Bend reliefs at flange corners: at least 1T wide and longer than the bend radius<\/strong> \u2014 they stop the tear that otherwise starts where a flange meets the parent face.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">These clearances cost nothing at design time and remove the two most common DFM comments we send on <a href=\"https:\/\/bravofabs.com\/sheet-metal-brackets\/\">bracket<\/a> and <a href=\"https:\/\/bravofabs.com\/sheet-metal-enclosures\/\">enclosure<\/a> drawings: &#8220;move hole away from bend&#8221; and &#8220;add bend relief.&#8221;<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Springback and Flange Height<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Springback<\/strong> is the metal&#8217;s elastic recovery after the punch lifts: a bend formed to 90\u00b0 relaxes open by a few degrees, more with harder materials and larger radii. Fabricators compensate by over-bending against measured tables \u2014 you don&#8217;t need to design for it, but you do need to accept its consequence: <strong>bend angles carry tolerance<\/strong> (\u00b11\u00b0 is a normal expectation in air bending), so avoid dimensioning schemes where three stacked bend angles must all land perfectly for a hole pattern to line up. Dimension critical features from a common face instead \u2014 the same logic as our guide to <a href=\"https:\/\/bravofabs.com\/cnc-machining-tolerances\/\">standard vs tight tolerances<\/a>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Flange height<\/strong> has a hard floor: the press brake needs material to grip on both sides of the die. Keep every flange <strong>at least 4\u00d7 material thickness<\/strong> tall (measured to the outside). Shorter flanges either can&#8217;t be formed at all or need secondary operations that multiply the bend&#8217;s cost.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Pre-Quote Design Checklist<\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>One uniform thickness<\/strong> across the whole part \u2014 sheet metal is folded, not sculpted.<\/li>\n<li><strong>Every inside radius \u2265 1T<\/strong> (1.5T for 5052, up to 2T for stainless), ideally one common radius for the whole part so one tool setup covers every bend.<\/li>\n<li><strong>Holes \u2265 2.5T + R and slots \u2265 4T + R from bend lines;<\/strong> holes \u2265 2T from edges.<\/li>\n<li><strong>All flanges \u2265 4T tall<\/strong>, bend reliefs \u2265 1T wide at flange corners.<\/li>\n<li><strong>Critical dimensions referenced from one face<\/strong>, not chained across multiple bends.<\/li>\n<li><strong>Send STEP + PDF drawing<\/strong> with material, thickness, finish, and quantity, per our <a href=\"https:\/\/bravofabs.com\/technical-drawings-in-custom-metal-fabrication\/\">technical drawing guide<\/a> \u2014 and let the fabricator apply calibrated K-factors to the flat pattern.<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Real-world example:<\/strong> an automation client sent a 1.5 mm 5052 sensor housing with six M4 clearance holes sitting 2 mm from a bend line \u2014 well inside the 2.5T + R zone. Rather than bounce the design back, our DFM review shifted four holes 3 mm outboard and converted the two that couldn&#8217;t move to post-bend drilling. The formed parts gauged round on every hole, and the fix cost one email instead of one scrapped batch.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Design It Once, Bend It Right<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Sheet metal rewards designers who respect five numbers: 1T radius, 2.5T + R hole clearance, 4T flanges, a calibrated K-factor, and a degree or two of springback. Follow them and your parts quote fast and form clean the first time. If you&#8217;d rather have a second pair of eyes, send your drawings: BravoFabs runs DFM review on every sheet metal RFQ \u2014 laser cutting, CNC bending, welding, and finishing under one roof in Dongguan, China \u2014 for industrial clients across Europe and North America, free with every quote.<\/p>\n\n\n<div class=\"wp-block-group has-light-gray-background-color has-background is-layout-constrained wp-container-core-group-is-layout-e86b207e wp-block-group-is-layout-constrained\" style=\"border-color:#1e73be;border-width:2px;padding-top:20px;padding-right:24px;padding-bottom:20px;padding-left:24px\">\n\n\n<h3 class=\"wp-block-heading\">Ready to Fabricate? Get a Sheet Metal Quote with Free DFM Review<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">BravoFabs turns sheet metal designs into parts \u2014 laser cutting, CNC bending with calibrated bend tables, welding, and powder coating or anodizing under one roof. Our ISO-certified facility in Dongguan, China serves industrial clients in Germany, the US, and across Europe, and every RFQ includes a free DFM review that catches bend-radius and hole-spacing issues before they cost you a batch.<\/p>\n\n\n\n<div class=\"wp-block-buttons is-layout-flex wp-block-buttons-is-layout-flex\">\n\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link has-white-color has-vivid-cyan-blue-background-color has-text-color has-background wp-element-button\" href=\"https:\/\/bravofabs.com\/contact\/\" style=\"border-radius:6px\">Request a Sheet Metal Quote \u2192<\/a><\/div>\n\n<\/div>\n\n\n<\/div>\n\n\n\n<div class=\"wp-block-group is-layout-constrained wp-container-core-group-is-layout-cbfb3306 wp-block-group-is-layout-constrained\" style=\"border-left-color:#2563eb;border-left-width:4px;border-left-style:solid;background-color:#f0f4ff;margin-top:32px;margin-bottom:0;padding-top:12px;padding-bottom:12px;padding-left:20px;padding-right:24px\">\n\n<h4 class=\"wp-block-heading\" style=\"font-size:15px;font-style:normal;font-weight:700;line-height:1.4;margin-top:0;margin-bottom:8px\">\ud83d\udd17 Related Services &amp; Articles<\/h4>\n\n\n\n<ul class=\"wp-block-list\" style=\"font-size:14px;line-height:1.7;padding-left:18px\">\n<li><strong><a href=\"https:\/\/bravofabs.com\/sheet-metal-fabrication-services\/\">Sheet Metal Fabrication Services<\/a><\/strong> \u2014 laser cutting, CNC bending &amp; welding from prototype to production<\/li>\n<li><strong><a href=\"https:\/\/bravofabs.com\/sheet-metal-enclosures\/\">Sheet Metal Enclosures<\/a><\/strong> \u2014 custom housings designed to these exact rules<\/li>\n<li><strong><a href=\"https:\/\/bravofabs.com\/sheet-metal-material-selection\/\">Sheet Metal Material Selection: Steel, Aluminum &amp; Stainless<\/a><\/strong> \u2014 pick the material before you pick the radius<\/li>\n<li><strong><a href=\"https:\/\/bravofabs.com\/custom-brackets-and-mounts\/\">Custom Brackets &amp; Mounts: Applications Across 5 Industries<\/a><\/strong> \u2014 these design rules applied in the field<\/li>\n<li><strong><a href=\"https:\/\/bravofabs.com\/technical-drawings-in-custom-metal-fabrication\/\">Technical Drawings in Custom Metal Fabrication<\/a><\/strong> \u2014 package your design for an accurate quote<\/li>\n<\/ul>\n\n<\/div>\n\n\n\n<div id=\"bf-lead-form-wrap\" style=\"margin-top:32px;padding:20px;background:#f0f4f8;border-radius:8px;text-align:center\">\n <p style=\"font-size:15px;font-weight:600;margin-bottom:12px;color:#1a1a2e\">Download Free Quick Reference PDF<\/p>\n <p style=\"font-size:13px;color:#555;margin-bottom:14px\">Printable reference sheet \u2014 keep it at your desk.<\/p>\n <button id=\"bf-lead-btn\" onclick=\"document.getElementById('bf-lead-form').style.display='block';this.style.display='none'\" style=\"background:#0693e3;color:#fff;padding:10px 24px;border:none;border-radius:6px;font-size:14px;font-weight:600;cursor:pointer\">Download Free PDF \u2192<\/button>\n <form id=\"bf-lead-form\" method=\"post\" action=\"\" style=\"display:none;margin-top:16px;padding:16px;background:#fff;border-radius:8px;border:1px solid #d1d5db;text-align:left\">\n  <input type=\"hidden\" name=\"bf_lead_magnet\" value=\"sheet_metal_design\">\n  <div style=\"margin-bottom:10px\"><input type=\"text\" name=\"name\" placeholder=\"Your Name *\" required style=\"width:100%;padding:8px 12px;border:1px solid #d1d5db;border-radius:4px;font-size:14px;box-sizing:border-box\"><\/div>\n  <div style=\"margin-bottom:10px\"><input type=\"email\" name=\"email\" placeholder=\"Work Email *\" required style=\"width:100%;padding:8px 12px;border:1px solid #d1d5db;border-radius:4px;font-size:14px;box-sizing:border-box\"><\/div>\n  <div style=\"margin-bottom:12px\"><input type=\"text\" name=\"company\" placeholder=\"Company (optional)\" style=\"width:100%;padding:8px 12px;border:1px solid #d1d5db;border-radius:4px;font-size:14px;box-sizing:border-box\"><\/div>\n  <button type=\"submit\" style=\"width:100%;background:#0693e3;color:#fff;padding:10px 24px;border:none;border-radius:6px;font-size:14px;font-weight:600;cursor:pointer\">Get PDF &#038; Download \u2192<\/button>\n <\/form>\n<\/div>\n\n\n<div class=\"wp-block-group has-light-gray-background-color has-background is-layout-constrained wp-container-core-group-is-layout-4c4e0579 wp-block-group-is-layout-constrained\" style=\"border-color:#1e73be;border-width:2px;margin-top:32px;margin-bottom:0;padding-top:20px;padding-right:24px;padding-bottom:20px;padding-left:24px\">\n<h3 class=\"wp-block-heading\">Need Sheet Metal Fabrication? Get a Quote with Free DFM Review<\/h3>\n<p class=\"wp-block-paragraph\">Send your CAD files and requirements to <strong>info@bravofabs.com<\/strong>. Our engineers review manufacturability, flag potential issues before production, and provide a detailed quote u2014 typically within 24 hours. Full inspection reports included.<\/p>\n<div class=\"wp-block-buttons is-layout-flex wp-block-buttons-is-layout-flex\">\n\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link has-white-color has-vivid-cyan-blue-background-color has-text-color has-background wp-element-button\" href=\"https:\/\/bravofabs.com\/contact\/\" style=\"border-radius:6px\">Request a Quote u2192<\/a><\/div>\n\n<\/div>\n<\/div><div class=\"rs-section\"><div class=\"rs-container\"><h2>Explore Related Manufacturing Services<\/h2><div class=\"rs-grid\"><div class=\"rs-card\"><a href=\"\/sheet-metal-fabrication-services\/\">Sheet Metal Fabrication<\/a><p>Laser cutting, bending, welding &amp; assembly. Prototype to production.<\/p><\/div><div class=\"rs-card\"><a href=\"\/cnc-machining-services\/\">CNC Machining Services<\/a><p>Precision CNC milling, turning &amp; 5-axis machining.<\/p><\/div><\/div><\/div><\/div>","protected":false},"excerpt":{"rendered":"<p>Key Takeaways Inside bend radius \u2265 1\u00d7 material thickness is the rule that prevents cracked bends \u2014 aluminum 5052 wants 1\u20131.5\u00d7, annealed stainless 1\u20132\u00d7, and harder tempers need more. K-factor (typically 0.3\u20130.5, commonly 0.33\u20130.44) locates the neutral axis and drives your flat-pattern math: BA = (\u03c0 \u00d7 angle\/180) \u00d7 (R + K \u00d7 t). Get [&hellip;]<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_titles_title":"Sheet Metal Design Guide: Bend Radius, K-Factor & Hole Spacing Rules | BravoFabs","_seopress_titles_desc":"Complete sheet metal design guide: minimum bend radius calculator, K-factor chart, hole-to-edge spacing rules, and flange height minimums. Free DFM checklist included.","_seopress_robots_index":"","_seopress_robots_follow":"","_seopress_robots_imageindex":"","_seopress_robots_snippet":"","_seopress_robots_primary_cat":"","_seopress_robots_breadcrumbs":"","_seopress_robots_freeze_modified_date":"","_seopress_robots_custom_modified_date":"","_seopress_robots_canonical":"","_seopress_social_fb_title":"","_seopress_social_fb_desc":"","_seopress_social_fb_img":"","_seopress_social_fb_img_attachment_id":0,"_seopress_social_fb_img_width":0,"_seopress_social_fb_img_height":0,"_seopress_social_twitter_title":"","_seopress_social_twitter_desc":"","_seopress_social_twitter_img":"","_seopress_social_twitter_img_attachment_id":0,"_seopress_social_twitter_img_width":0,"_seopress_social_twitter_img_height":0,"_seopress_redirections_value":"","_seopress_redirections_enabled":"","_seopress_redirections_enabled_regex":"","_seopress_redirections_logged_status":"","_seopress_redirections_param":"","_seopress_redirections_type":0,"_seopress_analysis_target_kw":"sheet metal design guide","footnotes":""},"categories":[40],"tags":[],"class_list":["post-2904","post","type-post","status-publish","format-standard","category-knowledge-base"],"_links":{"self":[{"href":"https:\/\/bravofabs.com\/wp-json\/wp\/v2\/posts\/2904","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bravofabs.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bravofabs.com\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/bravofabs.com\/wp-json\/wp\/v2\/comments?post=2904"}],"version-history":[{"count":4,"href":"https:\/\/bravofabs.com\/wp-json\/wp\/v2\/posts\/2904\/revisions"}],"predecessor-version":[{"id":3041,"href":"https:\/\/bravofabs.com\/wp-json\/wp\/v2\/posts\/2904\/revisions\/3041"}],"wp:attachment":[{"href":"https:\/\/bravofabs.com\/wp-json\/wp\/v2\/media?parent=2904"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bravofabs.com\/wp-json\/wp\/v2\/categories?post=2904"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bravofabs.com\/wp-json\/wp\/v2\/tags?post=2904"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}