Laser-Cut and Bent Brackets, Built to Print

From the model to the flat pattern

A bent bracket starts as a flat pattern, and the flat pattern depends on numbers that live on your print. The inside bend radius and the K-factor decide how much material each bend consumes. K-factor is the ratio of the neutral line’s location to the material thickness, and Wikipedia gives it as typically between 0.3 and 0.5, depending on the material, the type of bending and the tooling (source 3), and the tooling used changes how the sheet stretches as it bends (source 1). So two flat patterns unfolded from the same STEP with different values come out different lengths. Send the formed part as a STEP and let the flat pattern be developed against the radius and K-factor the bend will actually use; a flat DXF you unfolded yourself is fine as a reference, but the formed model and the print rule.

Put on the print what the model cannot say: inside bend radius, bend angle, bend direction (up or down relative to the flat), material and temper, thickness, and which faces or holes are the datums for inspection. A print that gives those, with its angle tolerance and the two mounting holes as the datum, can be quoted and inspected without a question. A bracket that starts as a sketch, a new sample part or photos has its CAD quoted as its own line. What file to send for laser cutting covers the drawing in general; this page is about what a bend adds. Machined brackets, milled from plate or bar, are a different part and live on custom machined brackets.

Bend radius, minimum flange and bend relief

Put the inside radius on the print. The more ductile the material, the smaller the radius it takes: Gerald Davis, writing in The Fabricator in 2017, gives an inside radius equal to the material thickness as the rule for steel, stainless and other ductile materials, and says 5052-H32 bends in about the same way as mild steel (source 1). 6061-T6 is the usual problem. The same article says it needs an inside radius of at least 6x the material thickness (source 1). A radius tighter than the sheet can take cracks the outside of the bend (source 1). If the radius on your print is tighter than the material will form, the quote says so and proposes one that will.

A flange has to be long enough to sit on the tooling. The same article gives 3x the material thickness as the recommended minimum flange for air bending on a press brake (source 1). Where a bend runs into an edge or stops partway across the part, the flat pattern carries a bend relief cut, as on the example part in that article, and its size is on the print. Reliefs go in the flat pattern before the cut, which is why the formed model is what to send.

Bend tolerances, and what they mean on a print

A bend carries tolerances of its own on top of the cut profile: the bend angle, the distance from a bend to an edge, the distance from a bend to a hole or internal cut, and any dimension that runs across a bend. Each one is stated on the quote. Name the material and thickness on the print, because both change how the sheet forms over the tooling.

Those tolerances belong on your print because the stack grows with every bend. A U-bracket with two 90° bends has an overall width that depends on both bend positions, so a dimension across both bends carries both bend tolerances. Steve Benson, as quoted in The Fabricator, notes that a ±0.006 in swing in sheet thickness can mean as much as 4 degrees of variation in an air-bent angle, and the same article notes that each added bend compounds the error (source 2). Where one dimension matters more, call it out tighter and name the datum it is measured from, and leave the rest at a general tolerance. A bracket that has to sit flat on a machined surface says so on the print. The laser profile tolerance itself is explained on laser-cut tolerances.

Holes near a bend, and hardware

A mounting hole cut in the flat close to a bend line can go out of round as the metal forms (source 4). When a mounting hole has to sit close to a bend, the flat pattern can carry a relief cut around it, or the hole can be drilled after forming as a machined feature located from the bent part. Both are print decisions and both are quoted as one part; the second is covered under secondary machining.

Hardware is installed per the print after forming. PennEngineering’s tech sheet on installing self-clinching fasteners near a bend says the holes should be made after bending so they do not go out of round, and that the fastener has to sit outside the bend radius, on sheet that is flat (source 4). Where a nut or stud has to sit close to a bend, the print can show its hole made after forming, as a machined feature; part numbers and hole sizes are on hardware insertion. Slots and tabs that cross a bend line are flagged on the quote.

Materials, grain direction and finishes

5052-H32 is the aluminum to draw for tight bends. 6061-T6 is the harder bend: it needs a larger radius than 5052-H32 or cold-rolled steel (source 1), and a tight radius cracks it. A bracket that must be 6061-T6 is still quotable; the quote will ask for a larger radius or propose 5052-H32 with the same finish. Mild steel in 1008 cold rolled or A36 hot rolled, and 304 or 316 stainless, are the other common answers, covered on laser-cut steel and laser-cut aluminum. Other alloys and plastics quoted on request. Name the grade on the print.

Rolled sheet has a grain direction. Sheet can crack instead of stretching depending on several variables, including the direction of the micrograin (source 1), and alternating grain direction from part to part adds angular variation (source 2). If a bend on your bracket is tight enough that grain matters, put the grain direction on the flat pattern as an arrow; without it, grain is not controlled. Finishes go on the formed bracket. A finish called out on the print is quoted with the part; powder coat, anodize and passivation are the usual callouts. Bending pressure can leave burnished, embossed lines that run parallel to the flange (source 1), so a cosmetic bracket says which faces are seen. How each finish treats a laser-cut part is on laser-cut finishing.

Inspection and what to send

Every bracket is inspected against your print before it ships: bend angles, flange lengths, formed dimensions, hole positions and hardware, each against its callout. One bracket and a production run get the same check, with lead time quoted per job and rush available. If a part doesn’t match the print, it’s remade or credited.

To get a quote, send a STEP of the formed part and a PDF print with material and temper, thickness, inside bend radius, bend angles, the datum, hardware part numbers and the finish. Any file type is accepted through the quote form; a flat DXF alone is quotable but will come back with questions about radius and direction. Brackets by material and by what they hold are grouped on brackets and mounts, machined brackets on custom CNC brackets, and the laser-cut parts hub lists every operation that can ride on the same order.

Sources

All accessed 4 October 2026. Where a figure here differs from your print, the print governs.

1. Gerald Davis, “What to know about sheet metal bend radius and minimum flange”, The Fabricator, 5 August 2017, updated 1 February 2023: thefabricator.com (tooling and stretch, grain, inside radius by alloy, minimum flange for air bending, tooling marks).

2. Tim Heston, “Reasonable tolerancing for press brake bending”, The Fabricator, 11 September 2018: thefabricator.com (sheet thickness variation and bend angle, error compounding with each bend, grain direction).

3. Wikipedia, “Bending (metalworking)”: en.wikipedia.org (K-factor and bend allowance).

4. PennEngineering, “PEM REF / C/L TO EDGE”, tech sheet, April 2019: pemnet.com/wp-content/uploads/sites/2/2022/06/CLtoEdgeRev419.pdf (fasteners installed close to a bend).