{"$schema":"nativecad-dfm-pack/1","id":"sheet-metal","title":"Sheet metal — brackets, enclosures, racks and press-brake formed parts","sector":"sheet-metal","version":"2026-09-03","summary":"Gauge and bend-radius tables, K-factor and bend-allowance formulas, flange/relief/hole-to-bend rules, hems/louvers/embosses, PEM and rivet hardware, 19-inch rack (EIA-310) and DIN-rail dimensions, NEMA/IP enclosure ratings, and the tests, standards, materials and recipes a laser-plus-press-brake part is held to.","aliases":["sheet metal","sheetmetal","bracket","rack","19 inch rack","rack ear","chassis","bend","flange","hem","louver","laser cut","press brake","u-bracket","l-bracket","sheet metal enclosure","metal enclosure"],"crossSector":false,"size":"core","sources":[{"id":"sendcutsend-sheet-cutting","title":"SendCutSend sheet cutting guidelines (laser/waterjet/router, min hole/radius)","url":"https://sendcutsend.com/guidelines/sheet-cutting/","accessed":"2026-09-03"},{"id":"sendcutsend-bending","title":"SendCutSend CNC bending service guidelines (materials, K-factor, bend limits, flange/relief)","url":"https://sendcutsend.com/services/cnc-bending/","accessed":"2026-09-03"},{"id":"sendcutsend-minmax","title":"SendCutSend min/max part sizes and per-material thickness","url":"https://sendcutsend.com/materials/min-max/","accessed":"2026-09-03"},{"id":"oshcut-capabilities","title":"OSH Cut capabilities (machines, materials, thicknesses, tolerances, tapping, bending)","url":"https://www.oshcut.com/capabilities","accessed":"2026-09-03"},{"id":"oshcut-minmax","title":"OSH Cut minimum/maximum material sizes","url":"https://www.oshcut.com/minimum-maximum-material-sizes","accessed":"2026-09-03"},{"id":"protolabs-sheet-metal","title":"Protolabs sheet metal design guide (bend radius, flange, relief, hem, hole-to-bend)","url":"https://www.protolabs.com/resources/design-tips/sheet-metal-design/","accessed":"2026-09-03"},{"id":"eia-310e","title":"EIA-310-E / ANSI/EIA 310 Cabinets, Racks, Panels and Associated Equipment (19-inch rack)","note":"no free official PDF; the 482.6mm/44.45mm/465.1mm numbers here are the same figures reproduced by Vertiv, APC and Wikipedia's 19-inch-rack technical summary of EIA-310-E","accessed":"2026-09-03"}],"entries":[{"id":"sheet-gauge-thickness-table","kind":"dimension","tier":1,"title":"Sheet gauge to thickness, 24-7 gauge (steel/aluminium/stainless)","summary":"Common sheet-metal stock spans 24ga (0.6mm) to 7ga (4.5mm): e.g. 18ga steel 1.21mm, 14ga steel 1.90mm, 11ga steel 3.04mm, 7ga steel 4.55mm; aluminium and stainless use different gauge-to-mm tables at the same gauge number.","applies":["sheet metal","bracket","enclosure","chassis"],"value":{"table":[{"gauge":24,"steelMM":0.61,"alMM":0.51,"ssMM":0.61},{"gauge":20,"steelMM":0.91,"alMM":0.81,"ssMM":0.95},{"gauge":18,"steelMM":1.21,"alMM":1.02,"ssMM":1.21},{"gauge":16,"steelMM":1.52,"alMM":1.29,"ssMM":1.52},{"gauge":14,"steelMM":1.9,"alMM":1.63,"ssMM":1.91},{"gauge":11,"steelMM":3.04,"alMM":2.3,"ssMM":3.04},{"gauge":7,"steelMM":4.55,"alMM":3.57,"ssMM":4.55}],"unit":"mm"},"basis":"Manufacturers Standard Gauge (steel/stainless) vs the separate Aluminum B&S gauge series, extended to the shop-floor 24-7ga range SendCutSend/OSH Cut stock","sources":["sendcutsend-minmax","oshcut-minmax"],"tags":["gauge","thickness","steel","aluminum","stainless"],"see":["materials/sheet-metal-gauge-table"]},{"id":"inside-bend-radius-soft-metals","kind":"rule","tier":1,"title":"Inside bend radius, soft steel and aluminium (1x thickness)","summary":"For dead-soft mild steel and soft aluminium (5052-H32), the minimum inside bend radius equals the material thickness t (1xt); tighter radii crack the outer fiber in air bending.","applies":["mild steel","5052-H32 aluminium","bracket","enclosure"],"value":{"typical":1,"unit":"ratio"},"basis":"Press-brake air-bend minimum-radius guidance for soft/annealed sheet stock (SendCutSend/Protolabs)","sources":["sendcutsend-bending","protolabs-sheet-metal"],"tags":["bend radius","soft metal","press brake"],"check":{"process":"sheet_metal","rule":"bend_radius"}},{"id":"inside-bend-radius-6061-t6","kind":"rule","tier":1,"title":"Inside bend radius, 6061-T6 aluminium (1.5-2x thickness)","summary":"6061-T6 aluminium needs a minimum inside bend radius of 1.5-2x material thickness (vs 1x for soft 5052) because the T6 temper is far less ductile; bending at radius <1.5t routinely cracks the outer surface.","applies":["6061-T6 aluminium","bracket"],"value":{"min":1.5,"max":2,"unit":"ratio"},"basis":"6061-T6's temper drops elongation well below annealed/H32 aluminium; vendor bending calculators publish a wider minimum radius for it","sources":["sendcutsend-bending"],"tags":["bend radius","6061-t6","aluminum"],"check":{"process":"sheet_metal","rule":"bend_radius"},"see":["materials/al-6061-t6"]},{"id":"k-factor-bend-allowance","kind":"dimension","tier":1,"title":"K-factor and bend allowance formula (worked example)","summary":"K-factor (neutral-axis location as a fraction of thickness from the inside) runs 0.33-0.5 depending on material and bend radius; bend allowance BA = angle(rad) x (radius + K x thickness) — e.g. 90deg bend, R=2mm, t=2mm, K=0.44: BA = 1.5708 x (2 + 0.44x2) = 4.52mm.","applies":["flat pattern","sheet metal"],"value":{"min":0.33,"max":0.5,"typical":0.44,"unit":"ratio"},"basis":"Standard sheet-metal bend-allowance derivation; 0.33 for tight/soft bends, 0.5 for thick or fully work-hardened material (matches sheet_fold's air-bending R/T table)","sources":["sendcutsend-bending"],"tags":["k-factor","bend allowance","flat pattern"]},{"id":"bend-relief-dimensions","kind":"rule","tier":1,"title":"Bend relief notch: width and depth","summary":"A bend relief notch needs width >= 1x material thickness and depth >= bend radius + 1x thickness, or the un-relieved corner tears or bulges when the flange forms.","applies":["bracket","chassis","enclosure"],"value":{"min":1,"unit":"ratio"},"basis":"SendCutSend: \"Bend relief notches reduce stress on inner radii and prevent corner tearing or bulging\" / \"Without proper relief, a part cannot be bent accurately\"","sources":["sendcutsend-bending"],"tags":["bend relief","notch","press brake"],"check":{"process":"scs_bend","rule":"bend_relief"}},{"id":"min-flange-length","kind":"rule","tier":1,"title":"Minimum flange length (die-support floor)","summary":"A formed flange needs a minimum length of about 4x thickness + inside radius (or 2.5xt + half the die width, die-dependent) or the flange drops into the V-die and will not form straight; e.g. 2mm steel, R2 die-width 16mm needs roughly 10mm minimum flange.","applies":["bracket","u-bracket","flange"],"value":{"min":4,"unit":"ratio"},"basis":"SendCutSend: \"Minimum flange length depends on material and thickness\"; die-support physics floor is half the V-die opening plus one thickness","sources":["sendcutsend-bending","protolabs-sheet-metal"],"tags":["flange","minimum length","press brake"],"check":{"process":"scs_bend","rule":"flange_support_ratio"}},{"id":"hole-to-bend-distance","kind":"rule","tier":1,"title":"Hole-to-bend-line minimum distance","summary":"Keep every hole or cut feature at least 2.5x material thickness plus the bend radius away from a bend centreline (>= half the V-die width, per SCS/OSH Cut), or the feature distorts as the sheet stretches through the bend.","applies":["bracket","chassis"],"value":{"min":2.5,"unit":"ratio"},"basis":"SendCutSend: \"keep cut features at least 1/2 the die width away from the centerline of each bend\"; expressed against thickness and radius as the generic die-independent floor","sources":["sendcutsend-bending"],"tags":["hole to bend","die keepout"],"check":{"process":"scs_bend","rule":"hole_to_bend"}},{"id":"min-punch-hole-diameter","kind":"rule","tier":1,"title":"Minimum punched/laser hole diameter (>= 1x thickness)","summary":"A punched hole diameter must be at least equal to the material thickness (die-shear floor) — a smaller punch shears and tears the sheet instead of cleanly cutting; laser-cut holes relax this to 0.5x thickness on some vendor lasers.","applies":["sheet metal","punch","laser cut"],"value":{"min":1,"unit":"ratio"},"basis":"ops/dfmRules.js sheet_metal pack: min_hole_diameter = 1x material thickness; SCS laser publishes 0.5x thickness for their fiber laser specifically","sources":["sendcutsend-sheet-cutting"],"tags":["hole diameter","punch","laser"],"check":{"process":"sheet_metal","rule":"min_hole_diameter"}},{"id":"laser-kerf-width","kind":"dimension","tier":1,"title":"Laser kerf width","summary":"A fiber-laser kerf (the width of material removed by the beam) runs 0.1-0.3mm depending on thickness and material; the minimum internal corner radius and minimum cuttable feature both scale off this number.","applies":["laser cut","sheet metal"],"value":{"min":0.1,"max":0.3,"unit":"mm"},"basis":"Fiber laser kerf published across sheet-cutting vendor guidelines; the beam cannot turn inside its own kerf so a sharper corner comes back rounded at ~kerf radius","sources":["sendcutsend-sheet-cutting"],"tags":["kerf","laser","tolerance"],"check":{"process":"scs_laser","rule":"min_internal_corner_radius"}},{"id":"corner-relief-dogbone-sheet","kind":"feature","tier":1,"title":"Corner relief (dogbone/T-bone) for CNC-routed sheet","summary":"A square internal corner cannot be CNC-routed by a round bit; add a 3.175mm dogbone (one bit-radius circle on the bisector) or T-bone relief so a square mating part still seats — cad_corner_relief models this, never fillet the corner.","applies":["cnc router","sheet metal","enclosure"],"value":{"typical":3.175,"unit":"mm"},"basis":"SendCutSend/OSH Cut router guidance: \"standard chamfers and fillets don't solve this; dogbones do\" — filleting a router corner adds material where there is already too much","sources":["sendcutsend-sheet-cutting"],"tags":["corner relief","dogbone","tbone","router"]},{"id":"rack-19-inch-width","kind":"dimension","tier":1,"title":"19-inch rack panel width (EIA-310)","summary":"A 19-inch rack panel is 482.6mm (19.00in) wide overall, with the mounting-hole centres 465.1mm (18.31in) apart — the panel is wider than the hole spacing by the ear width on each side.","applies":["19 inch rack","rack ear","rack panel"],"value":{"value":482.6,"unit":"mm"},"basis":"EIA-310-E standard rack width, reproduced across every 19-inch rack mechanical reference","sources":["eia-310e"],"tags":["rack","eia-310","19 inch","width"]},{"id":"rack-unit-height-1u","kind":"dimension","tier":1,"title":"Rack unit (1U) height","summary":"One rack unit (1U) is 44.45mm (1.75in) tall; panel heights are specified in whole U (1U, 2U, 3U...) and a panel's actual height is slightly under nU to clear the rail (e.g. 1U panel is typically 44.20mm).","applies":["19 inch rack","rack panel","rack ear"],"value":{"value":44.45,"unit":"mm"},"basis":"EIA-310-E defines 1U = 1.75in; three rack-unit hole groups repeat every 44.45mm","sources":["eia-310e"],"tags":["rack","1u","eia-310","unit height"]},{"id":"rack-mounting-hole-pattern","kind":"dimension","tier":1,"title":"Rack mounting hole spacing (6.35/15.88/15.88mm repeat)","summary":"Within each 44.45mm (1U) rack-rail hole group there are three holes spaced 6.35mm (0.25in), 15.88mm (0.625in), 15.88mm (0.625in) apart, repeating every U; hole centres sit 465.1mm apart across the rack width.","applies":["19 inch rack","rack ear"],"value":{"table":[{"gap1":6.35,"gap2":15.88,"gap3":15.88}],"unit":"mm"},"basis":"EIA-310-E universal hole spacing pattern for rack rails","sources":["eia-310e"],"tags":["rack","hole pattern","eia-310"]},{"id":"material-thickness-stock-range","kind":"rule","tier":1,"title":"Material thickness must fall in the vendor's stocked range","summary":"A sheet-metal design's thickness must land inside the shop's stocked range (SCS bending 0.030-0.250in / 0.76-6.35mm; OSH Cut laser 0.02-1.0in depending on material) — an unstocked thickness is refused, not approximated to the nearest stocked gauge.","applies":["sheet metal","laser cut","press brake"],"value":{"min":0.76,"max":6.35,"unit":"mm"},"basis":"SendCutSend CNC bending stocks 0.030-0.250in material; thicker or thinner stock is not on their bending line","sources":["sendcutsend-bending","oshcut-minmax"],"tags":["material thickness","stock range"],"check":{"process":"scs_bend","rule":"material_thickness"}},{"id":"part-envelope-sheet-laser","kind":"rule","tier":1,"title":"Sheet part envelope (minimum and maximum flat size)","summary":"A flat laser-cut part must be at least ~0.1in (2.5mm) and no larger than the vendor's sheet: OSH Cut sheets to 119in x 47in (3023 x 1194mm), SendCutSend bending flats 0.375in x 1.5in minimum up to 30in x 44in maximum.","applies":["sheet metal","laser cut","flat pattern"],"value":{"min":2.5,"max":3023,"unit":"mm"},"basis":"OSH Cut/SendCutSend published sheet and flat-blank size limits","sources":["oshcut-minmax","sendcutsend-minmax"],"tags":["part envelope","sheet size"],"check":{"process":"oshcut_laser","rule":"part_envelope"}},{"id":"min-internal-corner-radius-sheet","kind":"rule","tier":1,"title":"Minimum internal corner radius, cut sheet","summary":"An internal (concave) corner cut into flat sheet should carry a radius of at least 0.5x material thickness — sharper corners are the notch a formed part cracks from, and on a router route a truly square corner is not cuttable at all without a relief.","applies":["sheet metal","laser cut","bracket"],"value":{"min":0.5,"unit":"ratio"},"basis":"ops/dfmRules.js sheet_metal / oshcut_laser: min_internal_corner_radius = 0.5x material thickness","sources":["sendcutsend-sheet-cutting","oshcut-capabilities"],"tags":["internal corner","radius","stress riser"],"check":{"process":"sheet_metal","rule":"min_internal_corner_radius"}}]}