Chassis punches round and square disassembled

metalworking Metalworking is the process of shaping and reshaping metals in order 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 e ...

, a knockout punch, also known as a chassis punch, panel punch, Greenlee punch, or a Q-max, is a

hand tool A hand tool is any tool that is powered manual labour, by hand rather than a motor. Categories of hand tools include wrenches, pliers, cutter (disambiguation), cutters, File (tool), files, hammer, striking tools, chisel, struck or hammered tools, ...

used to punch a hole through

sheet metal Sheet metal is metal formed into thin, flat pieces, usually by an industrial process. Thicknesses can vary significantly; extremely thin sheets are considered foil (metal), foil or Metal leaf, leaf, and pieces thicker than 6 mm (0.25 ...

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

screw A screw is an externally helical threaded fastener capable of being tightened or released by a twisting force (torque) to the screw head, head. The most common uses of screws are to hold objects together and there are many forms for a variety ...

. There are three different drive systems: manual, ratchet, and

hydraulic Hydraulics () 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 counterpart of pneumatics, which concer ...

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 Zealand ...

. 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, cobalt ...

. 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