Chassis punches round and square disassembled

metalworking Metalworking is the process of shaping and reshaping metals to create useful objects, parts, assemblies, and large scale structures. As a term it covers a wide and diverse range of processes, skills, and tools for producing objects on every scale ...

, a knockout punch, also known as a chassis punch, panel punch, Greenlee punch, or a Q-max, is a hand tool used to

punch Punch commonly refers to: * Punch (combat), a strike made using the hand closed into a fist * Punch (drink), a wide assortment of drinks, non-alcoholic or alcoholic, generally containing fruit or fruit juice Punch may also refer to: Places * Pun ...

a hole through

sheet metal Sheet metal is metal formed into thin, flat pieces, usually by an industrial process. Sheet metal is one of the fundamental forms used in metalworking, and it can be cut and bent into a variety of shapes. Thicknesses can vary significantly; ex ...

. It is a very simple tool that consists of a punch, die, and screw. There are three different drive systems: manual, ratchet, and

hydraulic Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...

Operation

First a pilot hole is drilled slightly larger than 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 or square head and is driven using an allen key or

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. In the UK, Ireland, Australia, and New Zeala ...

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

ball screw A ball screw (or ballscrew) 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 bein ...

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

mechanical advantage Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for ...

of approximately 220:1 and can punch holes up to in diameter in 10 gauge

mild steel Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content is specified or required for chromium, cobal ...

. 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 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.

Size families and shapes

There are several sizing systems for these punches. The two most common are those sized for standard electrical knockout sizes and those that are for true dimensional holes. A 3/4 inch conduit size punch actually punches a hole that is approximately 1.1 inches diameter for 3/4 nominal size conduit. A dimensional size punch makes a hole very close to the indicated size. Punch sets are available on both imperial and metric sizes. Chassis punches are available in a number of shapes, round being the most common. Other shapes include square, hexagonal, and special shapes for thing such as holes with key tabs and D-sub connectors Special shapes often use bolts that are square or keyed and a separate nut on the punch end to ensure alignment of the punch and die.

References

{{reflist Metalworking hand tools