Sheet Metal Fabrication materials

The short answer Start with one controlled file set: a STEP model plus a dimensioned PDF, and state the material grade, quantity, finish and the date that matters. A DFM review comes back in 24 to 48 hours and standard geometry quotes within hours. Prototypes typically run 7 to 14 business days, low volume 2 to 3 weeks, and new hard tooling 4 to 8 weeks. The route from RFQ to packed parts A fabrication project is not one process, it is a route. The stages below are the order in which the decisions actually get made, and each one has a clear owner. Keeping it to one approval path is what makes a schedule believable. One approval path from RFQ release to packed parts. What to put in the first email Quotes slow down for one reason: the supplier is missing a fact that only the buyer has. An RFQ that carries the eight lines below can be priced in hours instead of days, and it eliminates the assumptions that later turn into cost disputes. Every line you leave out becomes an assumption the supplier has to make on your behalf. The single most useful thing to send is both a 3D model and a 2D drawing. The STEP file carries the geometry and lets the shop check bend relief and assembly relationships; the dimensioned PDF carries what the model cannot express - material, thickness, tolerances, threads, weld symbols, surface roughness and the revision you actually want built. Sending only one of the two usually produces a review that stops halfway. How long each size of job takes Lead time is driven by tooling and material availability far more than by machine time. A part that needs no new tooling can move in days; a part that needs a progressive die has to wait for the die. Add finishing time on top: anodising adds 3 to 5 days, decorative plating or hard coatings 7 to 14 days. Standard sheet metal work without new tooling ships in about 5 to 10 business days. A first-article inspection report, a capability study or an unusual alloy adds time to that, and the drawing decides which of those apply - the headline lead time does not. When you need a date you can plan around, ask what in your file set is driving the longest element, then decide whether to change it. Prototype, first article, production: three gates Each gate exists to catch a class of problem at the cheapest point where it can be caught. Skipping one moves the cost to the customer, usually at the end of the programme. GateWhat is checkedWhat it protects DFM reviewBend radii, hole-to-bend distance, tool access, coating build-upCost, before any tooling exists Prototype partsFit and function on real componentsDesign risk, before hard tooling First article inspectionEvery critical dimension against the drawing for the first part off the toolSpecification risk Tool qualificationCapability study on critical features as a repeatable processRepeatability risk across the run Pilot runProcess validated at near production volumeRamp risk when demand arrives For a new or modified part, prototyping before committing to hard tooling is the cheapest insurance available. A supplier that pushes straight to a hard tool without offering a prototype has removed your safety net, and that is worth treating as a caution rather than a schedule advantage. Six things that delay a project More than one revision in the file set. A model at revision C paired with a drawing at revision A guarantees a re-quote or a wrong part. Tolerance called out on everything. Blanket plus or minus 0.05 mm on non-functional features adds inspection time and cost without adding function. A tolerance table that distinguishes critical from general features quotes faster and cheaper. No quantity structure. Annual volume and batch size decide the process. A prototype quantity quoted against production volume, or the reverse, lands the project on the wrong route. Finish left to the last minute. Colour approvals, masking plans and outside coating queues are the longest common delay on an otherwise simple sheet metal assembly. Buyer-supplied parts with no date. An assembly waiting on a customer-furnished component cannot be scheduled, only started and set aside. Design frozen too late. Every change after a die is cut costs money and production time, and each modified station is priced separately. Ask for the fastest practical route, not the fastest sentence. A realistic date that holds is worth more than three revised dates. If a supplier cannot explain what is driving their lead time, they are guessing at it. Starting a project with SOMI Custom Parts Send the drawing package, an annual quantity and the date that matters, and we will come back with a DFM review, a process route, the flat pattern and a tolerance for each feature rather than a single number. Building the flat pattern, tooling and first-article inspection under one roof is what keeps the sequence decisions in quoting instead of on the shop floor: see sheet metal fabrication, metal stamping, or start with our inquiry form. Send your file set for a DFM review Scope and sources. Lead times, review windows and gate definitions above are typical published figures for custom metal fabrication in 2026 and were cross-checked against public fabrication ordering and quoting guides, including an RFQ to packed-parts route for sheet metal. Real schedules move with material availability, tooling queue, inspection level and finishing capacity, so treat these as planning ranges rather than commitments. Tolerance and inspection requirements are taken from the drawing package you issue.

The short answer Laser cutting makes the cut with a focused beam instead of a blade, so it cuts contours, not just straight lines, holds plus or minus 0.1 mm on a kerf of 0.1 to 0.25 mm, and needs no secondary finishing. Traditional methods are cheaper per metre: shearing cuts a straight edge fastest, plasma handles heavy plate, and waterjet cuts any thickness without heat. What actually differs The distinction is not precision against imprecision. It is a narrow kerf, low heat and full contour freedom against a broader kerf, more heat and a lower cost per cut. A mechanical shear separates material with a blade, leaves no kerf at all and cannot cut a curve. A plasma torch melts and blows material away, kerf widths of 1.5 to 3.5 mm and a large heat-affected zone. A waterjet erodes material with abrasive at up to 90,000 psi and leaves no heat at all. A laser sits between them: a kerf of 0.1 to 0.25 mm, a heat-affected zone of 0.05 to 0.20 mm, and edges clean enough to weld or paint without grinding. The numbers, method by method The comparison below is what a fabricator actually quotes against. Thickness ranges are production ranges, not machine maxima. Kerf width and heat-affected zone are what separate the processes once thickness is settled. CriterionFiber laserShearingPlasmaWaterjet Thickness range0.5 to 25 mm0.5 to 6 mm3 to 50 mm1 to 150 mm Cut tolerance±0.025 to 0.10 mm±0.20 to 0.50 mm±0.30 to 0.80 mm±0.08 to 0.20 mm Kerf width0.10 to 0.25 mmNo kerf loss1.5 to 3.5 mm0.80 to 1.20 mm Heat affected zone0.05 to 0.20 mmNone1.2 to 3.5 mmNone Edge angleWithin about 1 degreeSquare, with burr2 to 5 degrees of bevelSquare, slight texture Secondary workUsually noneDeburr the edgeGrind dross and bevelDry parts, abrasive waste Tolerance, kerf and heat Kerf is the width of material the process destroys, and it decides the smallest feature you can put on a part. A laser kerf of 0.2 mm means a 0.2 mm inside radius at minimum, while a plasma kerf of 3 mm leaves a visibly rounded corner that no drawing tolerance can fix afterwards. The rule of thumb for laser cutting is that the smallest practical hole is about one times the material thickness and the smallest slot about 0.8 times; going below that forces extra passes, more heat input and dross on the underside. Fiber laser holds the tightest band; plasma is the widest by a factor of ten. Heat matters for a different reason: it changes the material, not only the edge. Laser cutting leaves a heat-affected zone of 0.05 to 0.20 mm, which matters on thin stainless that will be bent afterwards because the zone is harder and less ductile. Plasma leaves a zone of 1.2 to 3.5 mm and a rough edge that usually needs grinding before welding. Waterjet has no heat-affected zone, which is why it is the route for hardened tool steel, titanium and any part where a metallurgical change would need re-qualifying. Speed and cost: laser is not always cheaper A 6 kW fiber laser cuts 16 gauge mild steel at around 8,000 mm per minute and 6 mm aluminium at about 3,500 mm per minute, with operating costs of roughly USD 15 to 30 per hour. Plasma runs around USD 20 to 40 per hour and is faster than laser on heavy plate - above about 12 mm a plasma torch clears 100 inches per minute or more where the laser has slowed to a fraction of its thin-sheet speed. Waterjet is the slowest at roughly 5 to 20 inches per minute with the highest consumable cost at USD 25 to 50 per hour, because it consumes abrasive garnet continuously. For repetitive hole patterns there is a fourth answer. A turret punch holds the same plus or minus 0.1 mm as a laser and nibbles a 50 mm slot in 16 gauge steel in under two seconds, and the economics flip in its favour somewhere between 200 and 500 pieces, above which the custom punch tooling pays for itself. Below that quantity, laser wins because there is no tooling at all. Choosing in four questions The first question that fits decides the method; later questions only refine the price. Straight cuts go to the shear, contours to the laser, thick plate to plasma, heat-sensitive stock to waterjet. When laser is the wrong answer The cut is a straight line and nothing else. Shearing is faster and cheaper per part, with no kerf loss to allow for. The plate is over about 25 mm. Above that, laser speed collapses and plasma or waterjet takes over on cost. The material cannot tolerate any heat. Hardened tool steel, some titanium alloys and laminated composites belong on a waterjet. The part needs a mirrored or textured edge. Laser leaves an oxide-free but characteristic cut face; waterjet leaves a matte, sandblasted surface that some specifications call for. Reflective alloys on an older source. Copper, brass and thick aluminium need a fiber source; a CO2 machine may struggle or produce poor edges. The hidden cost is not the cut, it is the cleanup. A laser edge at Ra 3.2 to 6.3 micrometres usually goes straight to paint or weld. A plasma edge needs grinding, and a sheared edge needs deburring, so compare the cost of the finished edge rather than the cost per metre of cut. Laser cutting at SOMI Custom Parts We run fiber laser cutting, plasma and waterjet for thick stock, turret punching for repetitive patterns and shearing for straight blanks, and we will tell you when a change of method would cost less without changing the part. Send a drawing and a quantity: see laser cutting, sheet metal fabrication, or open a project through our inquiry form. Ask for a cutting method comparison Scope and sources. Tolerances, kerf widths, heat-affected zones and cutting speeds above are typical published figures for commercial cutting equipment in 2026 and were cross-checked against public process comparisons for laser, plasma and waterjet cutting and shop capability data. Actual results depend on laser power, material grade, thickness, assist gas and nesting, so treat these as planning ranges rather than quotations. Cut edge quality was assessed against the general expectations of ASTM E165 liquid penetrant inspection where surface discontinuities matter.

The short answer The choice follows environment first, then load. Cold-rolled steel is the default when the part will be painted. Galvanised steel replaces it outdoors for roughly 10 to 20 percent more. Stainless 304 costs about four times cold-rolled steel and needs no coating; 316 about five times. Aluminium 5052 is a third of the weight of steel at around three times the price per kilogram. Start with the environment, not the datasheet Almost every material decision that goes wrong goes wrong in this order: someone picks steel for strength, then discovers the part lives outdoors, then adds a coating, then discovers the coating cannot survive the weld heat. Working the other way round resolves most parts in two questions. Where will the part be, and what load does it actually carry? Once those are fixed, the material list usually collapses to two candidates, and the remaining questions - forming, finish and volume - decide between them rather than opening the field again. The five families, and the numbers that separate them Density, tensile strength and cost index are the three figures worth comparing. Note that cost per kilogram is not cost per part: aluminium is roughly three times the price of galvanised steel per kilogram but only a third of the density, so a part sized by stiffness rather than by strength can come out close to even. Five families cover the large majority of fabricated parts. RequirementFirst choiceTrade-off to accept Lowest unit costSPCC cold-rolled steelRusts; needs paint or plating Outdoor corrosion without paintingGalvanised SECC or SGCCZinc fumes during welding Food, medical or coastal service304 stainlessAbout four times steel cost Chloride or salt exposure316 or 316L stainlessAnother 20 to 30 percent over 304 Lowest weight5052-H32 aluminiumLower stiffness than steel Strength in aluminium6061-T6Cracks on a tight bend radius Electrical or thermal dutyC1100 copper, C260 brassHighest material cost by a wide margin What each family actually costs Indicative 2026 prices sit at roughly USD 1.20 to 1.80 per kilogram for cold-rolled steel, 1.40 to 2.00 for galvanised, 4.50 to 6.50 for 5052 aluminium, 3.50 to 5.50 for 304 stainless and 5.00 to 7.50 for 316. The chart below turns that into a relative index so the gaps are visible at a glance. Material price per kilogram, indexed against galvanised steel at 1.0. Two levers move the material line on a quote more than the price per kilogram does. The first is scrap: nesting efficiency leaves 15 to 35 percent of the sheet unused depending on part shape, so a design that nests well beats a cheaper alloy. The second is thickness, because material cost scales linearly with it - dropping a 2.0 mm part to 1.5 mm cuts material cost by roughly a quarter if the load case still closes. On substitution, the biggest single saving available is replacing 304 stainless with galvanised steel on a part that does not need corrosion performance. That is worth 60 to 70 percent of the material cost. It is also the substitution most likely to be regretted, so it belongs in a drawing note rather than in a purchasing decision. Strength, weight and corrosion: three trade-offs Cold-rolled low-carbon steel forms easily, welds predictably and costs least, but it has no corrosion resistance of its own, so it either gets coated or it gets galvanised. Galvanised sheet carries a zinc barrier that protects scratches by sacrificial action, which is why it is the default for outdoor enclosures and ducts; the cost is that the coating boils at welding temperature, so galvanised assemblies are often riveted or clinched instead. Stainless works the opposite way. Austenitic grades are strong - 515 to 620 MPa against 270 to 410 MPa for mild steel - and resist corrosion through a chromium oxide layer that repairs itself in air. The practical distinction is 304 against 316: 316 adds molybdenum and is the grade for chlorides, so marine and chemical service, while 304 covers indoor and mildly corrosive work. Both work-harden, which is why stainless springs back more than mild steel and needs more press force or a larger bend radius. Aluminium is chosen for mass rather than strength. 5052 is the fabrication grade because it bends well and resists marine air; 6061-T6 is roughly twice as strong but cracks if formed on a tight radius, so a part that needs both strength and bends is usually designed as 6061 with the tight radii relieved, or formed in 5052 and heat-treated afterwards. Copper C1100 and brass C260 are reserved for conductivity, thermal performance and appearance. Choosing in four questions Run these in order. In practice questions one and two close most decisions, and the last two only confirm them. Environment and load are decided first; forming and finish refine the choice. Seven substitutions that cost more than they save 6061-T6 in place of 5052 on a formed part. The strength gain is real, and the bend cracking is more real. Copper or brass in contact with aluminium. In a wet environment the joint becomes a galvanic cell. Insulate the interface or pick one family. Uncoated steel outdoors. Cold-rolled steel without a coating is a maintenance item, not a finished part. Ignoring rolling direction. Bending across the rolling direction carries a far lower cracking risk than bending parallel to it. Forgetting that coatings add thickness. Anodising, plating and powder coating change dimensions, which matters on threads and press fits. Thickness chosen before the material. Aluminium needs more thickness than steel for the same stiffness, so copying a steel thickness onto aluminium loses stiffness rather than saving weight. Stainless specified for looks alone. A brushed 304 panel is roughly four times the material cost of a painted steel panel with the same geometry. Where the decision actually locks in. Material is settled at the drawing stage, because it decides the flat pattern, the bend radii and the weld procedure at the same time. Changing grade after tooling exists is a re-quote, not a swap. Material review at SOMI Custom Parts We hold carbon steel, galvanised steel, 301 / 304 / 316 stainless, 5052 and 6061 aluminium, copper and brass in the thicknesses our laser, bending, stamping and welding equipment runs, and we will say when a substitution changes the process rather than only the price. Send a drawing and an annual quantity: see sheet metal fabrication, metal stamping, or start with our inquiry form. Ask which sheet metal grade fits your part Scope and sources. Densities and tensile strengths are published mill data for the grades named; the cost index is built from indicative 2026 sheet prices per kilogram and was cross-checked against public sheet metal material and cost references including published sheet metal cost breakdowns. Metal prices move with the market, so the index is a planning tool rather than a quotation. Strength, elongation and corrosion performance vary with temper, thickness and supplier - confirm against the mill certificate for your lot.

The short answer Sheet metal fabrication runs from roughly 0.3 mm to 25 mm, and most production parts sit between 0.5 mm and 6 mm. The ceiling belongs to the process, not the shop: shearing and punching stop near 6 mm, press brake bending at about 12 mm, fiber laser cutting reaches 25 mm in mild steel, and plasma or waterjet take over above that. Cut edges normally hold plus or minus 0.1 mm. Where sheet ends and plate begins There is no single number, because the limit is not a property of the metal. It is a property of the machine that has to hold it, cut it and bend it. The practical dividing line most shops work to is about 6 mm. Below that, coil handling, turret punches and standard press brake tooling all behave normally, and the part nests comfortably on a 1,220 by 2,440 mm sheet. Above it, handling weight, cutting speed and bending tonnage start to change the economics faster than they change the geometry. That is why a straight answer is a set of ranges rather than one figure, and why the thickness on a drawing usually selects the process before any other feature does. Thickness range, process by process The bands below are production ranges, not laboratory maxima. Each process can be pushed past its band, but the cost per part stops being sensible, either because cut speed collapses or because the secondary work needed afterwards removes the advantage. Typical production bands in mild steel. Waterjet covers the widest range; shearing and punching the narrowest. Three of those bands decide most quotes. Fiber laser cutting is the default between 0.5 mm and 20 mm because nothing else combines that tolerance with that speed - a 6 kW source cuts 16 gauge mild steel at around 8,000 mm per minute. Press brake bending is usually the real constraint, not cutting: a 200 tonne brake handles roughly 6 mm across a one metre bend, 500 tonnes reaches about 10 mm, and 16 mm needs a 1,000 tonne machine. Waterjet is the escape route for anything above 25 mm or anything that must not see heat at all. The band decides the process and the tolerance Thickness does not only pick the machine. It also sets how much tolerance is realistic, and how much design care the feature needs. The table below is the version we use at quoting time. Matching the thickness band to a process is the single largest cost decision on a sheet metal part. Four checks before you commit a thickness Each of these can override the one before it, which is why the order matters. Cutting is checked first because it is the cheapest thing to change. Cutting, forming, joining and handling each impose a different limit on thickness. If the drawing saysCheck firstBecause 0.1 to 0.5 mmFixtures and nestingThin stock distorts in handling, not in cutting 0.5 to 3.0 mmHole-to-bend distanceHoles need 2.5 times the thickness clear of the bend 3.0 to 6.0 mmPress brake tonnageBending force rises with the square of the thickness 6.0 to 12.0 mmDie width and bend radiusWide V-die needed, inside radius at least one thickness 12.0 to 25.0 mmCutting method and edge taperLaser speed drops; plasma leaves a bevel 25 mm and upJoining and handlingThis is plate fabrication, not sheet metal work Where the thin end breaks down Minimum hole size follows the thickness. As a rule the smallest practical hole diameter is about one times the material thickness, and the minimum slot width about 0.8 times. Below that the cut needs extra passes, more heat and leaves dross on the underside. Handling becomes the process. Below about 0.5 mm the part bends under its own weight, so the cost sits in fixtures, magnetic handling and flat packing rather than in the machine. Welding has a floor too. Thin walls under roughly 0.8 mm are difficult to weld without burn-through, which pushes the design towards riveting, clinching or adhesive bonding. Where the thick end breaks down Edge taper appears. Laser perpendicularity stays within about one degree up to 10 mm, while plasma typically leaves a two to five degree bevel that needs grinding before a weld. Bend radius grows with thickness. One times the thickness is the practical minimum for mild steel, about 1.5 times for stainless, and around 2 times for 6061-T6 aluminium. Tight radii on thick stock crack on the outside of the bend. Tolerance loosens as thickness rises. The plus or minus 0.1 mm that is routine at 2 mm becomes plus or minus 1.5 mm at 30 mm, so features that must stay precise are usually machined after forming rather than formed. Long flanges stretch. Flanges grow by roughly 0.5 to 1.5 percent during forming, which shows up as a shift in hole position on long parts unless the flat pattern allows for it. Do not specify the tightest tolerance on the sheet. Tolerance and thickness are independent decisions. General tolerances to a standard block such as ISO 2768 class m cover undimensioned features, and calling out plus or minus 0.05 mm on a feature nothing depends on adds inspection cost without adding function. Thickness review at SOMI Custom Parts We cut with fiber laser, plasma and waterjet, form on press brakes from 0.5 mm to 12 mm, run progressive dies from 0.3 mm to 6 mm, and weld from 0.8 mm upwards, so the thickness on your drawing is matched to a route rather than forced onto one machine. Send the drawing with an annual quantity and we will come back with the process, the flat pattern and the tolerance each feature can actually hold: see sheet metal fabrication, laser cutting, or open a project through our inquiry form. Send a drawing for a thickness review Scope and sources. Thickness bands, tonnage figures and tolerance ranges above are typical published values for commercial sheet metal work in 2026 and were cross-checked against public process references including process and tolerance tables for sheet metal fabrication and shop capability data for fiber laser, plasma and waterjet cutting. Real limits move with material grade, machine power, tooling and part geometry, so treat these as planning ranges rather than quotations. Undimensioned features follow the general tolerance block on the drawing, for example ISO 2768 class m.

The short answer Stamping - also called pressing - forms parts from sheet metal or coil by driving a shaped tool, the die, into the material. It covers blanking, piercing, bending, drawing, forming and coining, and it runs on mechanical or servo presses. Because the geometry comes from the tool rather than from the machine's motion, stamped parts repeat very closely: ±0.025 mm is routine on progressive tooling, at rates from about 7 parts per minute on heavy gauge up to 1,500 strokes per minute on thin electrical terminals. The six operations that make up stamping "Stamping" is a family name, not a single process. Most parts combine two or more of the operations below inside one tool, which is exactly why a stamped part can carry several features that all have to line up. Six operations, usually combined. The tool, not the operator, fixes their relative position. From coil to packed part: the production line In a progressive line the material never stops moving. Coil is decoiled and straightened, a servo feeder advances it by an exact pitch, and the press completes one part per stroke. Deburring and inspection follow, but the dimensional work is already finished inside the die. The part is not touched between stations - that is where the repeatability comes from. How thick, how fast, how tight Thickness is what selects the press class, and the press class sets the output rate. A high-speed progressive line running 0.2 mm terminal stock behaves almost nothing like a heavy press forming 8 mm structural brackets, even though both are called stamping. Above about 6 mm, stamping becomes a dedicated heavy-press operation at 7 to 50 parts per minute. The numbers behind the diagram: progressive dies typically run 4 to 30 stations. A 12-station die processing 0.5 mm steel at 500 strokes per minute produces 30,000 parts per hour. Material utilisation lands at 75 to 90 percent of coil weight with a well-nested strip layout, against 20 to 50 percent for machining from solid bar. Where stamping stops working Tooling is the entry ticket. Progressive dies run USD 10,000 to 250,000+ and take 8 to 20 weeks to build. Below roughly 50,000 to 100,000 pieces per year the investment does not pay back. The design has to be close to frozen. Each modified station costs USD 5,000 to 80,000 plus lost production time. Coil width and part size are bounded. Strip runs about 5 to 500 mm wide and finished parts commonly 5 to 300 mm. Larger structural parts go to single-stage or transfer stamping. No undercuts, no hollow sections. A punch must be able to reach the feature and withdraw from it. Burrs are inherent. Every sheared edge has one. If the print forbids a burr above a stated height, plan a deburring operation and its cost. Watch the tool, not the last part. A punch that has worn at station six keeps producing parts that pass a glance and fail a gauge. In-process dimensional sampling during long runs is what catches it; final inspection only tells you how many were bad. Stamping at SOMI Custom Parts We build single-stage, compound and progressive tooling from 0.2 mm to 6 mm stock, in carbon steel, 301 / 304 / 316 stainless, 5052 and 6061 aluminium, copper and brass. Strip layout, tool design, first-article dimensional reports and in-process sampling sit with the same team that runs the press: see metal stamping, sheet metal fabrication, or send a drawing through our inquiry form. Ask for a stamping tooling quote Scope and sources. Press speeds, station counts, tooling ranges and tolerance bands above are typical published values for commercial metal stamping in 2026, cross-checked against Xometry's progressive die stamping reference and die-manufacturing comparison data. Values shift with part geometry, material and press selection, so treat them as planning ranges rather than quotations. Feature tolerances apply where they are called out; undimensioned features follow the general tolerance block on the drawing.

The short answer Metal sheet fabrication is the group of processes that turn flat sheet or coil into finished parts without machining material away. Cutting produces the blank, forming creates the three-dimensional geometry, joining holds the pieces together, and finishing protects the surface. Fibre laser cutting handles roughly 0.5 to 25 mm mild steel, most production parts run between 0.5 and 6 mm, and feature tolerances land around ±0.1 to ±0.2 mm unless the drawing calls for tighter. What the process actually involves A fabricated part is built in stages, and each stage changes what the next stage can hold. Cutting sets the blank outline; every hole, notch and slot is located from the same datum. Forming then introduces the third dimension, and this is where most tolerance is lost or won. Joining adds material or creates a metallurgical bond. Finishing is the last chance to fix a cosmetic defect, because after coating the surface is sealed. Cutting, forming, joining and finishing - each stage constrains the next. How thick can the metal be, and on which process? Thickness is the first constraint to check, because it selects the process rather than the other way round. Laser cutting, plasma cutting and waterjet all cut sheet, but their useful ranges are very different, and bending has its own limit set by the press brake and the material's ductility. Typical production ranges in mild steel. Waterjet covers the widest band; bending is the narrowest. Two practical consequences follow. First, above roughly 12 mm, forming becomes a press-forging or heavy-plate operation rather than ordinary sheet work. Second, the thinner the material, the more the part behaves like foil during handling - so fixtures and nesting matter more than the machine's rated capacity. How sheet metal fabrication compares with other processes The common assumption is that sheet metal is the "cheap" process. It is more accurate to say it is the process with the lowest tooling barrier, which is a different claim. Where a progressive die needs USD 10,000 to 250,000 before the first part exists, a fabricated assembly needs fixtures and press brake tooling that cost a fraction of that. Volume and tooling separate the processes more than achievable tolerance does. Where sheet metal fabrication stops working Minimum bend radius. As a rule of thumb the inside radius should be at least one material thickness for mild steel, and larger for high-strength or T6 aluminium. Tighter than that and the outer surface cracks. Holes too close to a bend. Keep hole edges at least 2.5 times the thickness plus the bend radius from the bend line, or the hole distorts when the material stretches. Springback. Metal relaxes after the punch lifts, so the die has to over-bend. High-strength and austenitic stainless spring back the most and may need a second strike. No undercuts or internal cavities. If a feature cannot be reached by a punch or a tool from one of two directions, fabrication is the wrong route. Tolerance ceiling. ±0.1 to ±0.2 mm is realistic for fabricated features. If the print calls for ±0.01 mm, that feature belongs on a machining operation. The expensive mistake is mixing processes on one feature. A bend that must hold a machined bore's position has to be machined after forming, never before. Sequence is a cost decision, not a shop-floor preference. Design rules that decide cost Use standard sheet thicknesses. Stepping to the next stock size instead of a nominal 3.0 mm can cut material cost and lead time immediately. Standardise bend radii. One or two radii across the part means one or two press brake setups instead of five. Keep bends in one direction where possible. Re-orienting the part between bends adds handling and setup time on every unit. Add the bend allowance to the flat pattern. The flat blank equals the sum of the legs plus the bend allowance, where BA = angle × (r + K × t) × π/180 and K typically falls between 0.33 and 0.50. Design for the finish. Anodising and plating add thickness, so threads and press-fit bores need allowance or post-finish machining. Sheet metal fabrication at SOMI Custom Parts We run laser cutting, press brake forming, stamping, welding and surface finishing under one roof, which means the sequence problem above gets solved at quoting rather than after the first article. Send a drawing and an annual quantity and we will come back with the process route, the flat pattern, and the tolerance each feature can actually hold: see sheet metal fabrication, metal stamping, or start a project through our inquiry form. Send a drawing for a process review Scope and sources. Thickness ranges, tolerance bands and tooling figures above are typical values published for commercial sheet metal work in 2026 and were cross-checked against Xometry's sheet metal process references. Real numbers move with material, machine and part geometry, so treat these as planning ranges rather than quotes. Undimensioned features follow the general tolerance block on the drawing, for example ISO 2768 class m.

The short answer The workhorses of sheet metal fabrication are cold-rolled low-carbon steel (SPCC, DC01), galvanised steel (SECC, SGCC), austenitic stainless 304 and 316, aluminium 5052 and 6061-T6, and copper C1100 with brass C260. The split is simple: steel covers strength at the lowest cost, stainless covers corrosion, aluminium covers weight, and copper or brass cover conductivity and appearance. Everything else is a variation on those four trade-offs. The grades most shops actually hold Material choice is usually decided by what is available in the required thickness, not by the datasheet. The grades below are the ones stocked as standard sheet in most fabrication shops, which is why quoting tends to land on them. Five material families cover the large majority of fabricated parts. Steel and stainless: strength against corrosion Cold-rolled low-carbon steel is the default because it forms easily, welds predictably and costs the least per kilogram. Its weakness is that it has no corrosion resistance of its own, so it either gets a coating or it gets galvanised. Galvanised and galvannealed sheet carry a zinc barrier that survives scratches by sacrificial action, but the coating boils at welding temperature, which is why galvanised assemblies are often riveted or clinched instead. Stainless works in the opposite direction. Austenitic grades are strong, non-magnetic and resist corrosion through a chromium oxide layer that self-repairs in air. The practical distinction is 304 versus 316: 316 adds molybdenum and is the grade for chlorides, so marine and food-processing environments, while 304 covers general indoor and mildly corrosive service. Both work-harden, which is why stainless springs back more than mild steel and needs more press force or a larger bend radius. Aluminium, copper and brass: weight and conductivity Aluminium is chosen for mass, not for strength. 5052 is the fabrication grade because it bends well and resists corrosion in marine air; 6061-T6 is roughly twice as strong but cracks if it is bent on a tight radius, so if a part needs both strength and bends, it is usually designed as 6061 for the flat features and formed in 5052, or heat-treated after forming. Copper C1100 and brass C260 are reserved for conductivity, thermal performance and appearance; they form beautifully but cost several times more than steel and their corrosion products are visible. RequirementFirst choiceWatch out for Lowest unit costSPCC cold-rolled steelRusts - needs a coating Corrosion without paintingSECC galvanised or 304 stainlessZinc weld porosity; stainless cost Salt or chloride exposure316 / 316L stainlessRoughly 1.4 to 1.8x the cost of 304 Lightest weight5052-H32 aluminiumLower stiffness than steel Strength in aluminium6061-T6Cracks on tight bends Electrical or thermal dutyC1100 copper, C260 brassHighest material cost How thick, and what each material allows Thickness availability narrows sharply as thickness rises, and that is a cost and lead-time effect rather than a technical one. Copper and brass top out earliest; stainless and aluminium remain available well past 6 mm but tooling wear and press force climb with them. Ranges commonly held in stock. Ordering outside them means mill lead time. Choosing in four questions Working through these in order resolves most material decisions before a datasheet is opened. Volume sets how much tooling the part can carry, environment sets the corrosion grade, and the last two questions usually pick between two candidates rather than open the field again. Once volume and environment are fixed, only one or two grades remain viable. Where material choice goes wrong Substituting 6061-T6 for 5052 in a formed part. The strength gain is real; the bend cracking is more real. Heat-treat after forming, or keep 5052. Mixing metals that will touch. Copper or brass in contact with aluminium in a wet environment produces galvanic corrosion at the joint. Insulate the interface or pick one family. Specifying uncoated steel outdoors. Cold-rolled steel without a coating or galvanising is a maintenance item, not a finished part. Ignoring forming direction. Bending across the rolling direction reduces cracking risk by a wide margin compared with bending parallel to it. Forgetting finish thickness. Anodising, plating and powder coating all add dimension, which matters on threads and press fits. Material support at SOMI Custom Parts We keep carbon steel, galvanised steel, 301 / 304 / 316 stainless, 5052 and 6061 aluminium, copper and brass in the thicknesses our forming and stamping equipment runs, and we will tell you when a substitution changes the process rather than just the price. Send a drawing and a quantity: see sheet metal fabrication, metal stamping, or start with our inquiry form. Ask which grade fits your part Scope and sources. Material property notes and the stock thickness ranges shown above reflect commercial availability for the grades listed in 2026 and were cross-checked against published sheet metal process and material references, including Xometry's sheet metal material data. Strength, elongation and corrosion performance vary with temper, thickness and supplier, so confirm against the mill certificate for your lot. Undimensioned features follow the general tolerance block on the drawing.