A knockout punch, also known as a chassis punch or a Q-max, is a hand tool

Hand tool

A hand tool is a device for performing work on a material or a physical system using only hands. The hand tools can be manually used employing force, or electrically powered, using electrical current...

 used to punch

Punching

Punching is a metal forming process that uses a punch press to force a tool, called a punch, through the workpiece to create a hole via shearing. The punch often passes through the work into a die. A scrap slug from the hole is deposited into the die in the process. Depending on the material being...

 a hole through sheet metal

Sheet metal

Sheet metal is simply metal formed into thin and flat pieces. It is one of the fundamental forms used in metalworking, and can be cut and bent into a variety of different shapes. Countless everyday objects are constructed of the material...

. It is a very simple tool that consists of a punch, die

Die (manufacturing)

A die is a specialized tool used in manufacturing industries to cut or shape material using a press. Like molds, dies are generally customized to the item they are used to create...

, and screw

Screw

A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...

. They are three different drive systems: manual, ratchet

Ratchet

Ratchet may refer to:* Ratchet , a mechanical device that allows movement in only one direction* Ratchet, a tool also known as a socket wrench* Ratchet , a music instrumentIn film and television:...

, and hydraulic drives.

Operation

First a pilot hole

Pilot hole

A pilot hole is a smaller hole drilled into a material prior to a larger hole being drilled, widening the hole to the desired width. Drilling a pilot hole prevents a larger drill bit from slipping on the material - a potential safety hazard, as well as an increased likelihood of the work being...

 is drilled of the same diameter as the screw of the knockout punch. Then the die is placed on the screw and the screw is inserted into the pilot hole. The screw is then threaded into the punch and the screw tightened until the punch is drawn completely through the sheet metal.

The manual system uses a screw that has a standard hex head and is driven using a wrench

Wrench

A wrench or spanner is a tool used to provide grip and mechanical advantage in applying torque to turn objects—usually rotary fasteners, such as nuts and bolts—or keep them from turning....

. A manual knockout punch can handle holes from 0.5 inch. The ratchet system has a custom ratcheting wrench that uses a ball screw

Ball screw

A ball screw is a mechanical linear actuator that translates rotational motion to linear motion with little friction. A threaded shaft provides a helical raceway for ball bearings which act as a precision screw. As well as being able to apply or withstand high thrust loads, they can do so with...

 to make the process faster and easier. This type of system has a mechanical advantage

Mechanical advantage

Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Ideally, the device preserves the input power and simply trades off forces against movement to obtain a desired amplification in the output force...

 of approximately 220:1 and can punch holes up to 3 in (7.6 cm) in diameter in 10 gauge mild steel. A hydraulic system is much bulkier and heavier than the other systems but it is the easiest to use and can make holes up to 6 in (15.2 cm) in diameter. It is a two piece system where the dies are attached to the ram which is connected to the hydraulic unit via a flexible hose.