Design for manufacture: sheet metal.

Most of what drives the cost and lead time of a sheet metal part is decided at the design stage, long before it reaches the workshop. The guidance below covers the choices that matter most. They are rules of thumb rather than hard limits, and we will confirm the exact figures for your material and thickness when we quote.

Bends and flanges

Forming is where a flat profile becomes a three-dimensional part, and it is the step most sensitive to design. A few habits keep parts accurate and affordable.

• Keep the internal bend radius consistent across a part. As a rule of thumb, an internal radius roughly equal to the material thickness forms cleanly in most mild steels.
• Give flanges enough length to form. A flange shorter than about four times the material thickness plus the bend radius is difficult to hold accurately.
• Keep holes and cut-outs back from bend lines. Features too close to a bend distort as the metal forms; allow at least around three times the thickness plus the bend radius between a hole and a bend.
• Where you can, design bends to run in the same direction, so the press brake is set once rather than reoriented for every feature.

Holes, slots and edges

• Keep hole diameters at or above the material thickness. Very small holes in thick material are slow to produce and can add cost.
• Allow space between a hole and the edge of the part, around twice the material thickness, so the edge does not bulge or tear.
• Keep a similar margin between adjacent holes and slots to leave a strong web of material between them.
• Countersinks, threads and inserts are all straightforward, but tell us up front so we can plan the right sequence.

Tolerances

Tolerance is one of the biggest levers on cost. Laser profiling holds tight tolerances comfortably, but forming introduces small variations, and those variations stack up across multiple bends.

• Call out the few dimensions that are genuinely critical, rather than tightening the whole drawing.
• Expect a little more variation on formed features than on flat, laser-cut ones, and on parts with many bends than on simple ones.
• If a part has to mate with another, tell us which faces or holes must line up, and we will hold those.

Material and finish

The material and finish are best decided early, because they change how a part is designed, handled and priced.

• Choose thickness for the job, not the heaviest to hand. Extra thickness adds weight, cost and forming load.
• Decide the finish before the design is fixed. A visible, grain-matched stainless part is handled very differently from one that will be painted or hidden.
• If corrosion or hygiene matters, that points to a material and a finish; see our materials guide for the trade-offs.