Technical Guide for Sheet Metal Fabrication
Standard engineering tolerances, material restrictions, and primary layout setups. At Spike Metal, we believe that a flawless product begins with a manufacturing-ready design.
To ensure your custom designs are fully optimized for seamless production, we highly recommend reviewing our comprehensive engineering standards.
1. Uniform Wall Thickness
Since sheet metal parts are formed and bent from a single, flat sheet of metal, your 3D CAD design must maintain a uniform wall thickness throughout all sections. This is a critical principle for the correct operation of CNC machinery and for maintaining overall dimensional accuracy.

2. Processable Materials & Sheet Size Limits
Our facility is fully equipped to process a wide range of premium raw sheet stocks with strict dimension limits bound to metal thickness and press brake boundaries.
| Material Stock Parameter | Maximum Production Threshold |
|---|---|
| Maximum Flat Blank Layout | 39 in. × 47 in. (990.6 mm × 1,193.8 mm) |
| Maximum CNC Press Brake Length | 47 in. (1,193.8 mm) |
| Standard Processable Materials | Aluminum, Brass, Copper, Stainless Steel, Carbon Steel (Cold Rolled & HRPO) |
3. Standard Manufacturing Tolerances
If an explicit engineering drawing or print has not been provided by the customer, we will manufacture the product directly from the 3D model to the following standard tolerances:
| Manufacturing Feature | Standard Tolerance Limit (Metric / US) |
|---|---|
| Bends (Angularity Precision) | ±1° |
| Linear Dimensions (Excl. Bends) | ±0.1 mm (±0.004 in.) |
| Forming & Bending Locations | ±0.4 mm / ±0.508 mm (±0.020 in.) |
| Bend to Hole or Local Feature Location | ±0.2 mm / ±0.381 mm (±0.015 in.) |
| Hole & Slot Diameters / Edge to Edge Size | ±0.127 mm (±0.005 in.) |
| Diameters with Inserts (PEM nuts) | ±0.0762 mm (±0.003 in.) |
| Features Separated by 2+ Bends | ±0.762 mm (±0.030 in.) |
| Surface Roughness Standard | ±3.2 μm Maximum |

4. Engineering Parameters of Bending
Bending dynamics are defined by specific calculations of material behavior. During the forming cycle, the neutral axis remains unchanged, and its relative displacement dictates the K-Factor used to calculate exact flat patterns in CAD software.
| Bending Method (Radius Range: 0 to 1×t) | Reference K-Factor Value |
|---|---|
| Air Bending - Soft Aluminum Alloys | 0.33 |
| Air Bending - Hard Alloys / Stainless Steel | 0.40 |
| Air Bending - Carbon Steel (C.R / H.S) | 0.35 |
| Bottom Bending - Soft Aluminum | 0.42 |
| Bottom Bending - Stainless Steel | 0.46 |
5. Inside Bend Radius Selection
We maintain a strict industry-standard tolerance of ±1° on all bend angles. Our standard workshop tooling supports cost-effective radius profiles readily available on the shop floor.
| Standard Factory Inside Radii | Tooling Lead Time |
|---|---|
| 0.030 in. (0.762 mm) / 0.060 in. (1.524 mm) | Standard Stock (Immediate) |
| 0.090 in. (2.286 mm) / 0.120 in. (3.048 mm) | Standard Stock (Immediate) |
6. Minimum Flange Length & Z-Offset Height
To form a precise, consistent bend, the sheet metal blank must establish three points of contact with the press brake die tooling to secure stable sheet tracking and prevent angular deformation.
| Sheet Thickness (t) | Min Flange Length (b) | Min Z-Offset Height (X) |
|---|---|---|
| Up to 1.0 mm | 10.0 mm | 35.0 mm |
| 1.25 mm | 10.5 mm | 35.0 mm |
| 1.50 mm | 11.0 mm | 36.0 mm |
| 2.00 mm | 13.5 mm | 36.5 mm |
| 3.00 mm | 17.0 mm | 39.5 mm |

7. Feature Proximity Clearance to Bends
Material naturally stretches in close proximity to a bend axis. Any geometric cutout or feature placed inside this active deformation zone is at extreme risk of stretching, warping, or tearing into deformed teardrop profiles.
| Geometric Feature Type | Minimum Distance Clearance to Bend Axis |
|---|---|
| Round Hole Edge Spacing | ≥ 5 × Material Thickness (t) + Bend Radius (r) |
| Rounded Slot Edge Spacing | ≥ 4 × Material Thickness (t) + Bend Radius (r) |

8. Permanent Hardware Insertion Spacing
Integrating high-strength threads via self-clinching fasteners (PEMs) or CD studs requires strict placement away from active deformation zones to maintain localized structural strength and ensure parallel compressive seating.
| Hardware Positioning Parameter | Minimum Required Clearance |
|---|---|
| Insert Hole Edge to Sheet Boundary | ≥ 2 × Material Thickness (t) [Prevents Bulging] |
| Center-to-Center Insert Spacing | ≥ 6 × Material Thickness (t) [Protects Load Grip] |
| Insert Center to Bend Tangent Line | ≥ 5 × t + Bend Radius + Hem Radius |
9. Hem Feature Design & Safety
Hems are excellent for hiding raw burrs, removing sharp untreated edges to ensure safe manual handling, and doubling local thickness in areas requiring high structural rigidity or tight structural joints.
| Hem Design Profile | Minimum Inside Diameter | Minimum Return Flange Length |
|---|---|---|
| Open Hem Configuration | ≥ 1.0 × Material Thickness (t) | ≥ 4 × Material Thickness (t) |
| Closed Hem Configuration | Equal to Material Thickness (t) | ≥ 6 × Material Thickness (t) |
| Teardrop Hem Profile | Equal to Material Thickness (t) | ≥ 4 × Material Thickness (t) |

10. Sizing Rules for Notches and Tabs
Notching removes metal from a raw outer boundary to create component clearances and improve tool access, while protruding tabs facilitate seamless component alignment before welding.
| Feature Type | Minimum Width Criterion | Maximum Depth / Length Bound |
|---|---|---|
| Shearing Notches | ≥ 1.0 mm or 1.0 × t (Whichever is greater) | ≤ 5 × Notch Width [V-Notch: ≤ 2 × Width] |
| Protruding Tabs | ≥ 2.0 mm or 2.0 × t (Whichever is greater) | ≤ 5 × Tab Width [Prevents Buckling] |

11. Countersink Clearances & Dimensions
Countersinks allow flathead fastener screws to sit flush with or below the sheet metal surface. We provide both machined countersinks (via drill presses) and formed countersinks (via punch press tooling).
| Countersink Process | Major Diameter Factory Tolerance | Recommended Minor Diameter |
|---|---|---|
| Machined Processing | ±0.254 mm [Major Dia: 2.3 mm to 12.7 mm] | 2/3 × Material Thickness (t) |
| Formed Press Processing | ±0.381 mm [Standard Angles: 82°, 90°, 100°, 120°] | ±0.381 mm (Tooling bound) |
12. Industrial Surface Finishing Treatments
Our facility provides a comprehensive suite of finishing options, including Anodizing, Electroplating, PVD Coating, Sandblasting, and premium Electrostatic Powder Coating to enhance longevity and corrosion resistance.
Frequently Asked Questions
Fiber laser cutting pricing at Spike Industrial Group is based on key factors such as material type (carbon steel, stainless steel, aluminum), sheet thickness, cutting length (or number of holes), and CNC machine runtime. For press brake bending services, the number of bend lines and part complexity are also calculated.
For parts that "only require laser cutting", the best submitted formats are DXF and DWG. For "bent parts", the STP format is the most suitable choice, and for "assemblies and industrial machines", providing an STP file or the original SolidWorks file is recommended. From an engineering standpoint, SolidWorks is the best and most precise tool in sheet metal design; additionally, CorelDRAW (CDR) formats can also be processed in our facility for decorative designs and graphic projects.
The K-Factor and bend deduction depend on variables such as material type, exact material thickness, internal bend radius, and press brake die opening. Adhering to these parameters in the file design prior to cutting prevents dimensional errors in the part after bending.
As a standard principle in Design for Manufacturability (DFM), the diameter of any hole or internal cut should not be less than the thickness of the sheet metal itself (preferably equal to or greater than it); otherwise, edge quality degrades and part stability is compromised.
Yes, as a comprehensive sheet metal fabrication center, Spike Industrial Group performs all stages—from fiber laser cutting, CNC press brake bending, and welding to oven-cured electrostatic powder coating—seamlessly and with strict quality control to minimize costs and delivery times.
Nesting optimization, using commercially available sheet thicknesses, reducing the number of assembled parts by designing more bends instead of welding, and adhering to DFM principles are the primary ways to reduce manufacturing costs at Spike.
To have an accurate flat pattern, design must be performed in specialized Sheet Metal environments (such as SolidWorks), and actual workshop parameters including precise sheet thickness, internal bend radius of the press brake tool, and bend calculation coefficients (K-Factor or Bend Deduction) must be accurately applied in the software so that after laser cutting and bending, the part dimensions are exact and free of assembly tolerances.
The K-Factor is the ratio of the neutral axis location to the sheet thickness, representing the metal's behavior during deformation. Bend Allowance (BA) is the arc length of the bend in the neutral zone, and Bend Deduction (BD) is the amount subtracted from the sum of the outer flange lengths to reach the flat pattern dimensions, which designers use to accurately calculate the initial blank length.
In carbon steel laser cutting, using oxygen as an assist gas causes an exothermic reaction and increases cutting speed; whereas for stainless steel and aluminum, high-pressure nitrogen gas is used so that the edges remain completely bright, oxidation-free, and ready for welding or painting.
This phenomenon usually occurs when the internal bend radius is less than the material's allowable limit or when the bend line is parallel to the sheet's rolling direction (fiber direction). The solution is to increase the internal bend radius according to the DFM chart and orient the bend lines perpendicular to the rolling direction.
Laser welding features extremely high speed, highly localized heat input (minimal thermal distortion and warping), excellent penetration depth, and a clean surface finish, which minimizes the need for finishing operations, grinding, and surface polishing.
If a hole or laser cut is too close to the bend line, it will deform during the press brake process. As an engineering standard, the distance from the edge of the hole to the bend line should be at least equal to the sheet thickness plus 1.5 times the bend radius.