Sheet Metal Design Handbook — Australian Design Guidelines

A practical reference covering Australian sheet metal design guidelines for bends, holes, flanges, tolerances and fabrication — plus ASTCAD’s manufacturing-ready sheet metal design services.

Last reviewed: May 2026

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What is this handbook?

This page provides a practical reference for engineers, designers and fabricators working with sheet metal in Australia. It covers the core design rules for common sheet metal features — bends, curls, dimples, flanges, holes, notches, ribs and welds — and includes ASTCAD’s reference handbook PDF for download. All guidelines reference typical Australian manufacturing tolerances and are consistent with AS 1734 (aluminium and aluminium alloys — flat sheet, coiled sheet and strip), AS 1397 (steel sheet and strip), and AS 1553 (covered electrodes for welding mild steel).

ASTCAD uses these guidelines as the foundation for every sheet metal design service we deliver — producing SolidWorks, Autodesk Inventor and CATIA models with flat patterns, bend tables, DXF files, and 2D fabrication drawings ready for Australian laser cutting, press brake and stamping operations.

Sheet Metal Design Handbook — reference PDF

The embedded handbook below covers design rules for all major sheet metal features. Use it as a quick reference during the design phase to avoid common manufacturability issues before drawings reach the fabrication floor.

Sheet Metal Design Handbook — Australian Design Guidelines

Key sheet metal design guidelines

Bends

Bend design is the most critical sheet metal manufacturability factor. Key rules:

Multiple bends on the same plane should run in the same direction to simplify tooling
Minimum bend radius in low-carbon steel: one-half the material thickness or 0.80 mm — whichever is larger
Bend angle tolerances: ±0.5° at a location adjacent to the bend
Avoid large sheet metal parts with small bent flanges — the flange-to-part ratio affects springback and tool access
Minimum distance from a bend to a hole: 2× material thickness + bend radius

Holes and slots

Minimum hole diameter: equal to material thickness or 1.00 mm — whichever is greater
Minimum hole-to-edge distance: proportional to hole shape and material thickness
Minimum hole-to-bend distance: 2× material thickness + bend radius
Minimum slot width: material thickness or 1.00 mm — whichever is greater
Slot-to-bend distance: depends on slot length and orientation relative to bend line

Flanges

Minimum flange height is directly related to material thickness, bend radius, and bend length
Minimum bend relief width: 1× material thickness or 1.50 mm — whichever is greater
For hem flanges: minimum return height ≥ 4× material thickness; closed hems risk fracture and solution entrapment during finishing — design open hems where possible

Embossments, dimples and ribs

Maximum dimple diameter: 6× material thickness; maximum depth: half the inside diameter
Flat embossment maximum depth: internal radius + external radius
V-embossment maximum depth: 3× material thickness
Rib maximum inside radius: 3× material thickness at maximum depth equal to the inside radius
Minimum rib-to-rib spacing: 10× material thickness + sum of radii

Welding

Spot welding restricted to coplanar surfaces
Minimum weld-to-weld spacing: 10× material thickness (20× ideal)
Minimum weld-to-edge distance: 2× spot weld diameter
Lap-welded joints trap plating solutions — raise welds on embossed areas by 0.3 mm to allow flushing
Prefer PEMs over threaded inserts for thin sheet metal

Plating and finishing

Outside sharp corners accumulate 2× the plating thickness of flat surfaces — adjust hole tolerances accordingly
Tapped holes must be re-tapped after plating to maintain thread accuracy
Design drain holes for plating solution flushing
Anodising masking of specific areas is not recommended — design parts to accept full anodise treatment

ASTCAD sheet metal design capabilities

ASTCAD designs sheet metal parts and assemblies using SolidWorks (Sheet Metal module), Autodesk Inventor, CATIA and Pro/Engineer (Creo). Our deliverables include:

3D solid models with correct material thickness, K-factor, and bend allowance applied
Flat pattern drawings with accurate unfolded dimensions for laser, plasma and waterjet cutting
2D fabrication drawings with GD&T, bend notes, hole charts, and material callouts
DXF/DWG files for direct import into CNC cutting and press brake programming
STEP/IGES files for CAM and tooling design
Bill of materials including material specification (grade, thickness, finish)

We follow Design for Manufacturing and Assembly (DFMA) principles throughout, minimising bend operations, reducing scrap, and ensuring every design can be fabricated by Australian sheet metal shops without special tooling or rework.

Australian standards referenced in sheet metal design

AS 1734 — Aluminium and aluminium alloys: flat sheet, coiled sheet and strip
AS 1397 — Continuous hot-dip metallic coated steel sheet and strip
AS/NZS 1554.6 — Structural steel welding: welding stainless steels
AS 1553 — Covered electrodes for welding mild steel
AS 1100.101 — Technical drawing: general principles
AS 4024 — Safety of machinery: relevant for sheet metal guarding and enclosures

Frequently asked questions

What is the minimum bend radius for sheet metal in Australia?

The minimum bend radius depends on material type, grade and thickness. For low-carbon mild steel (the most common sheet metal in Australian fabrication), the minimum inside bend radius is one-half the material thickness or 0.80 mm — whichever is larger. For stainless steel, minimum bend radius is typically 1× material thickness. For aluminium alloys, it varies by temper — 5052-H32 typically requires a minimum of 1× to 1.5× material thickness. Always confirm the minimum bend radius with your fabricator before finalising drawings, as press brake tooling and material batch variation can affect achievable radii.

What is K-factor in sheet metal design?

K-factor is the ratio of the neutral axis location to the material thickness during bending. It determines how much material stretches during a bend and is used to calculate the flat pattern (developed length). A K-factor of 0.33 is used for sharp bends; 0.41–0.44 is typical for air bending of mild steel. In SolidWorks and Inventor, K-factor is set in the sheet metal parameters and applied automatically to flat pattern calculations. Using the correct K-factor for your material and tooling combination ensures flat pattern dimensions are accurate for laser cutting without adjustment.

What file formats do you deliver for sheet metal fabrication?

ASTCAD delivers sheet metal documentation in the formats required by your fabrication shop: DXF for laser/plasma cutting, STEP or IGES for CAM programming, PDF for shop floor reference, DWG for integration with AutoCAD workflows, and native SolidWorks or Inventor files where direct CAD access is needed. All flat pattern DXF files include bend lines as separate layers and are scaled 1:1 for direct import into nesting software.

Can you design sheet metal enclosures to IP ratings?

Yes. ASTCAD designs sheet metal enclosures to specified IP (Ingress Protection) ratings per AS 60529 (equivalent to IEC 60529). Achieving a target IP rating requires careful attention to: gasket groove geometry and compression ratios, cable gland and connector cutout tolerances, overlap and seam design for IP65/IP66 ratings, and drain hole sizing for IP67/IP68 underwater applications. We produce detailed drawings that specify gasket material, compression set requirements, and surface finish standards to ensure your enclosure meets its rated protection class when fabricated.

How do I get a quote for sheet metal design?

Contact ASTCAD with your project requirements — material, thickness, quantity, required standards, and any existing sketches or reference drawings. We will provide a fixed-price quote within 24 hours. For complex assemblies with multiple parts, we can quote by component or as a complete package including BOM and assembly drawings.

Related services and resources

Sheet metal design services — end-to-end design and drafting for Australian fabricators
Fabrication drawings — shop drawings for steel, aluminium and mixed-material structures
Mechanical drafting services — full mechanical CAD design and drafting
2D drafting services — precision 2D drawings for manufacturing
AS 1657 reference — Australian standard for platforms, walkways and ladders

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