EKO Basics

Electrical Knockouts are a common application used in the manufacturing of electrical enclosures. 


What is an EKO?

EKO stands for Electrical Knockout. EKO’s are widely used in electrical enclosures and are a very common form made in sheet metal shops. 

How are EKO’s made in sheet metal? 

An EKO tool cuts the sheet metal and pushes it either up or down to a height roughly equal to one material thickness. The slug is held into the sheet with uncut holding tabs.

How do I know what size to order? 

The electrical industry has common conduit sizes. EKO’s are routinely made for these common sizes.  However, EKO tools must be ordered for the actual size of the hole, not the conduit size. See conversion chart below:

Standard Conduit or Pipe Size (I.D.) Actual O.D of Pipe Actual Hole Size
1/4" 0.540" (13.72mm) 0.575" (14.61mm)
3/8" 0.675" (17.15mm) 0.718" (18.24mm)
1/2" 0.840" (21.33mm) 0.875" (22.22mm)
3/4" 1.050" (26.67mm) 1.125" (28.57mm)
1" 1.315" (33.40mm) 1.375" (34.92mm)
1-1/4" 1.660" (42.16mm) 1.734" (44.04mm)
1-1/2" 1.900" (48.26mm) 1.969" (50.01mm)
2" 2.375" (60.32mm) 2.469" (62.71mm)
2-1/2" 2.875" (73.02mm) 2.937" (74.59mm)
3" 3.500" (88.90mm) 3.594" (91.28mm)
3-1/2" 4.000" (101.6mm) 4.123" (104.7mm)

Form Up or Form Down? 

Choose the form direction based on whether the slug needs to be on the inside or outside of your finished product. If you’re fabricating an electrical box, be sure to take your bend directions into account.

How is the slug held in the sheet?

An EKO tool does not cut the entire diameter. A small holding tab (or multiple tabs depending on size of knockout) remains in the sheet uncut. These tabs are large enough to hold the slug in the sheet, but small enough to allow removal in the field. When a customer selects to use “standard tabs” (recommended), the tool will be manufactured to meet industry standards.

  • UL SPECS: No more than .005 (.12mm) of light between main sheet and KO. Must be flattened partially back into the sheet and painted to be watertight.
  • Test: Must hold 10 lbs. of pressure opposite nip

Custom holding tabs are also available. If this option is selected, the customer is responsible for ensuring the tabs both hold the slug in the sheet and allow for removal in the field.

Required Information to Order an EKO Tool

To ensure your EKO tool is designed to create the highest quality form consistently and reliably, we need the following information:

  • Machine make and model
  • Material type and thickness
  • Form Up or Form Down
  • Actual size of knockout (if conduit size – must specify)
  • Spacing to closest adjacent form
  • Standard or custom holding tabs

Download Round EKO Template.
Download Shaped EKO Template. 

For more information on EKO tools from Wilson Tool, please contact our Tooling Technicians or visit wilsontool.com/eko

March 16, 2020