Punching

Punching creates holes and simple profiles in sheet metal using punch-and-die tooling, enabling fast, repeatable production of flat parts with patterned features.

Overview

Punching uses a punch-and-die set in a press or CNC turret to shear holes and profiles out of flat sheet metal. It excels at repeating features: hole arrays, knockouts, slots, louvers, and simple exterior contours. CNC turret punching can mix many standard tools in one program, giving good flexibility without custom hard tooling.

Choose punching for flat parts in thin to medium-gauge sheet where you need lots of holes or repeated cutouts and moderate to high production volumes. Setup costs are low when standard tooling covers your geometry, and cycle times are very fast once programmed. Tradeoffs: complex contours may require nibbling, leaving slight scallops, and you’re limited by available tool shapes and sizes. Very tight tolerances, sharp internal corners, or very thick materials may push you toward other processes or hybrid routes (punching plus secondary ops).

Common Materials

  • Cold rolled steel
  • Galvanized steel
  • Stainless steel 304
  • Aluminum 5052
  • Aluminum 6061
  • Copper brass

Tolerances

±0.005"

Applications

  • Electronics enclosures and chassis panels
  • Mounting brackets with hole and slot patterns
  • Ventilation grilles and perforated panels
  • Control panels with button and connector cutouts
  • Sheet metal blanks for formed housings
  • DIN rail and rack-mount components

When to Choose Punching

Use punching for flat sheet-metal parts with many repeatable holes or cutouts in thin to medium gauges and medium to high production volumes. It’s ideal when your geometry fits standard punch shapes and you want fast cycle times and low per-part cost. It also suits parts that will be bent or formed later from a punched flat blank.

vs Cutting

Choose punching over laser or other cutting when you have high part quantities with repetitive holes or standard shapes, and material thickness is within typical sheet ranges. Punching will usually give lower cost per part and shorter cycle times, especially for dense hole patterns and standard profiles.

vs Forming

Punching handles the flat pattern operations before any bends or 3D forming. Use punching when you need accurate holes, slots, and knockouts that must align after forming, then send the punched blank to forming presses or brakes.

vs Fastening

Choose punching when you can design tabs, slots, and locating features directly into the sheet instead of relying on extra fasteners. Punched features can reduce hardware count and assembly time by enabling snap fits, interlocks, and self-locating parts.

vs Welding (Sheet Metal)

Use punching to add holes, slots, and alignment features that simplify downstream welding and fixturing. Well-placed punched features can reduce weld length, improve fit-up, and minimize the amount of welding required in an assembly.

vs Hydroforming

For flat parts or simple preforms, punching is far more economical and faster than hydroforming. Reserve hydroforming for deep, contoured shapes; use punching to produce flat blanks with all required openings before any complex forming.

Design Considerations

  • Favor standard punch diameters and slot sizes to avoid custom tooling and reduce lead time
  • Keep hole-to-edge distance at least 1.5x material thickness (more for large holes) to prevent distortion and breakout
  • Maintain sensible minimum web widths between holes, typically at least material thickness or the punch diameter, whichever is larger
  • Avoid extremely small holes in thick material; as a rule of thumb, minimum hole diameter should be at least material thickness
  • Design external profiles with generous radii or straight segments; tight inside corners and complex curves may require nibbling and increase cycle time
  • Specify realistic tolerances and clearly mark critical-to-function features so the shop can select appropriate tooling and inspection levels