Punching

Punching creates holes, cutouts, and formed features in sheet metal using press tooling, delivering fast cycle times and low per-part cost at volume.

Overview

Punching is a sheet metal process that uses a press and matched punch/die tooling to shear holes and profiles, and in some cases add simple forms (louvers, embosses, extruded holes). Modern CNC turret punch presses index standard tools for many features in one program, while mechanical/servo presses excel at repeat high-speed hits.

Choose punching for flat parts with lots of repeated holes, slots, and cutouts, especially when you need short cycle time and consistent feature-to-feature spacing. It’s a strong fit for brackets, panels, and enclosures in low-to-high volume, particularly when features match standard tooling.

Tradeoffs: design freedom is limited by available punch shapes/sizes, material thickness, and tonnage. Burr and shear rollover are inherent and may need deburr. Tight edge quality and complex outside profiles often push parts to laser/waterjet, while large 3D shapes push toward forming methods.

Common Materials

  • Mild steel
  • Stainless steel 304
  • Aluminum 5052
  • Aluminum 6061
  • Galvanized steel
  • Copper

Tolerances

±0.005"

Applications

  • Electrical enclosure panels
  • Chassis and bracket plates
  • HVAC duct flanges and panels
  • Rack-mount front panels
  • Control cabinet knockouts and gland plates
  • Perforated guards and vent panels

When to Choose Punching

Punching fits flat sheet metal parts with many repeated features where standard tooling can hit fast and cheaply. It works best when hole sizes, slot widths, and patterns are consistent across the design and volumes justify setup/programming. Plan for deburr and realistic positional tolerances driven by sheet movement, tool wear, and fixturing.

vs Cutting

Choose punching when your part has many holes/slots or repeated cutouts that match standard tools and you want the lowest cycle time per feature. Punching is typically faster and cheaper per hole than continuous-path cutting, especially on perforated patterns.

vs Forming

Choose punching when the part is primarily flat and you need 2D features (holes, slots, knockouts) with optional light forms like louvers or embosses. Punching avoids dedicated bend tooling and multi-step forming when 3D geometry isn’t required.

vs Fastening

Choose punching when the goal is to create holes, tabs, or pilot features that enable fast assembly without adding separate components. Punching can also prep features for hardware insertion (e.g., PEM®) so assembly is repeatable and fixturing is simpler.

vs Welding (Sheet Metal)

Choose punching to build features into a single blank—holes, tabs, and vent patterns—so you reduce welded add-ons and post-weld rework. Better feature consistency up front improves fit-up and lowers weld time.

vs Hydroforming

Choose punching when you need high-throughput 2D feature creation rather than a deep, smooth 3D shell. Punching keeps tooling and part cost lower for panels and brackets that don’t need complex drawn geometry.

Design Considerations

  • Keep minimum hole diameter at or above material thickness (larger for stainless) to reduce distortion and tool wear
  • Place holes and slots at least ~1.5x material thickness from edges and bends to prevent tearing and breakout
  • Use standard hole sizes and slot widths that match common turret tooling to avoid special tools and longer lead time
  • Call out deburr/burr direction requirements and cosmetic sides; punching leaves rollover and burr that may need secondary finishing
  • Avoid dense perforation too close to bends or edges; leave web to maintain flatness and prevent oil-canning
  • Specify material, thickness, grain direction (if critical), and flatness needs up front so the shop can choose the right press and nesting