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A variety of functions may be performed by any press, depending upon the tooling.

Typical press operations and other terms referring to press features and functions are defined below:

Arch Press

A type of press similar to a straight-side press with an enlarged bed and bell-shaped frame. The arch press can accommodate larger sheets of metal.


The main foundation and supporting structure upon which the operating parts of the machine are mounted and guided.


The shaping of sheet metal by straining the metal around a straight axis. A bending operation compresses the interior side of the bend and stretches the exterior side. Flanging, hemming, and seaming are all bending operations.


Blanks are produced from the shearing or cutting of outside contours or shapes out of sheet or strip stock. For larger production runs, blanking is often done in multiple dies, and is combined with other operations such as piercing and forming in combination and progressive dies.

Bolster Plate

A plate or block attached to the top of the press bed where the die is fastened. In some rare cases the die is fastened directly to the bed.

C-Frame Press

Another term for the gap-frame press.


The specified amount of force that a press is capable of exerting near the bottom of its stroke in order to carry out a stamping operation.


A squeezing operation usually performed in a closed die in which the metal is forced to flow and fills the shape and profile of the die. There is a definite change in metal thickness.

Cold Working

The shaping of metal at temperatures much lower than the metal's molten state, often at room temperature. Cold working adds certain properties to the metal, such as increased strength and improved surface finish.

Connecting Rod or Connection

See Pitman


The device in some mechanical presses that connects the ram to the flywheel.


An operation in which the open end of a can or shell is forced tight over or around a mating part. This type of work is limited largely to assembly operations.


The upper portion of a press containing the drive mechanisms or cylinders that guide the reciprocating motion of the ram.


The forming of an edge, having a circular cross section along a sheet, or around the end of a shell or tube. This operation is sometimes called false wiring.


The main drive of a hydraulic press that uses fluid to force the motion of a piston encased within the device.

Deep Drawing

Forming of deep recessed parts from sheet material by means of a plastic flow of the material worked in presses and dies.


The amount of deviation from a straight line or plane when a force is applied. Effective presses reduce the amount of deflection during operation.


1. A tool used on a press for any operation or series of operations, such as forming, drawing, piercing and cutting. The upper member (or members) are attached to the slide (or slides) of the press, with the lower member clamped or bolted to the bed or bolster, shaped so that the material placed between them is cut or formed when the press makes a stroke. 2. The female part of a complete die assembly as described in (1). 3. A tool for cutting external threads.

Die Cushion

An attachment or press accessory which gives additional motion or pressure required in many compound press operations. The pressure medium can be rubber, springs, air or liquid (usually oil). Air (pneumatic) cushions are the most commonly used. Uses include blank holding, drawing, maintaining uniform pressure on a die part, knock-out, and stripping. Typically mounted in order on the press bed, they can sometimes be mounted on the top of a press slide flange.

Die Height

The closed height of a die during the working portion of the press or completed operation in the die. Die Height is measured from the top of the bolster plate to the bottom of the slide.

Die Set

The collective assembly of upper and lower die shoes, guide pins and bushings, and punch and die holders.


For sheet metal, a forming operation that transforms a flat disc of stock into a hollow cup with an enclosed bottom. Drawing operations can also create boxes and more intricate shapes as well.


Essentially a disk arranged to rotate around a center, not the center of dish but parallel to it. An eccentric should crank with a crankpin of such size that it contains or surrounds the shaft. The eccentric with its strap or connection is used in the eccentric press and for driving auxiliary attachments, such as lift outs and various types of feeds.

Eccentric Drive

A drive that uses an offset section to power the reciprocating motion of the ram.


A process for producing raised or sunken designs in sheet metal by means of a male and female die.


A process in which pressure is applied to a slug of metal causing the metal to flow either up around the punch (toothpaste tubes) or down in the direction of pressure (cartridge cases - Hooker process).


A bending operation that bends the edge of a part to add stiffness. Flanging most often creates a 90 degree bend in the metal.


A wheel used on an engine or machine with a rotation energy or inertia able to prevent excessive or sudden changes in speed. In modern mechanical presses the flywheel is usually belted, chained or geared to the driving motor. A clutch is mounted on or within the flywheel.


The structure of a press that supports the ram above the base and guides the reciprocating motion of the ram.

Gap-Frame Press

A type of press with a C-shaped frame suspending the crown over the bed and an open portion in the front. The open front of the gap-frame press offers easy access to the die set.


Guides or shoes that insure the proper sliding fit between two machine parts and which usually are adjustable for taking up excessive wear, e.g., press gibs that guide the press slide.

Horn Press

A type of press with a cylindrical projection designed to position sheet metal parts for secondary operations.

Hot Working

The shaping of metal at temperatures close to the metal's molten state. Metal that has been hot worked is often left with a rough, scaly exterior.

Hydraulic Power

Power derived from the motion and pressure of a fluid, such as water or oil.

Hydraulic Press

A press that is driven by hydraulic power. Most hydraulic presses are driven by one or more cylinders that use fluid pressure.


A machine control process used to adjust and set dies and other tools by precisely controlling the working members of the press in short increments usually by rapidly engaging and disengaging the clutch or using electric or pneumatic push buttons.


A process in which the wall thickness of the shell is reduced without changing the O.D. of the shell (cartridge case work for example).


Slitting and forming a pocket shaped opening in sheet metal, without removing metal.

Link Motion

A modified slide motion that produces either constant velocity or increased slow down through the working part of the press stroke.

Lower Die Shoe

The lower plate of a die set that contains the cavity into which the punch shears the sheet metal.

Mechanical Power

Power derived from the use of solid tooling and machinery.

Mechanical Press

A press that is driven by mechanical power. Most mechanical presses are driven by a flywheel, crank, and clutch.

Metal Forming

The plastic deformation of a metal in order to produce a useful shape. Sheet metal can be formed through operations that shear, stretch, bend, or compress the metal.


Reducing the diameter of a portion of the length of a cylindrical shell or tube.

Open-Back Inclinable Press

A type of gap-frame press with a bed and frame that can be tilted backwards to encourage the removal of parts after they are separated from the strip.


A general term for cutting (shearing or punching) openings, such as holes and slots in sheet material, plate or parts.  Similar to blanking; the slug or piece produced by piercing is scrap, whereas the blank produced by blanking is the useful part.  In both cases the burr is opposite.


A connecting rod to convey motion and pressure from a revolving crank of eccentric to a sliding or swinging member, such as a slide or lever. A press connecting rod.

Pneumatic Die Cushion

Pneumatic (air) attachment, consisting essentially of a cylinder piston, pressure plate and accessories generally used with a press for clamping, blank holding or ejecting.


A machine with a stationary base and an upper ram that moves along a vertical axis to shear, bend, or form sheet metal.

Press Bed

The stationary portion or "table" of the press to which the bolster is attached.

Press Brake

The friction mechanism used to stop or control the motion of a press, feed or other mechanism.

Press Capacity

Rated press capacity is the tonnage pressure the slide can safely exert at the bottom of the stroke.  Mechanical press capacity is typically based on  the bending capacity of the main shaft (crank, toggle, or eccentric shaft).

Press Clutch

A coupling used to connect or disconnect a driving machine-member, such as a shaft or wheel, to or from a driven machine-member, such as another wheel or shaft. The engaging or disengaging can be done by a hand operated controlling device operated manually or automatically.

Progressive Dies

A series of two or more dies arranged in line for performing two or more operations on a part, one operation (single or compound) performed in each die, at each station. Work in the form of a strip is usually fed to progressive dies automatically by a roll feed.

Punch / Stamp

The tool typically attached to the upper portion of the die set that shapes or penetrates the sheet metal.


A shearing operation that creates an open hole in sheet metal by separating an interior section. The removed metal section is discarded scrap.


The second operation following deep-drawing operations, in which cups are deepened and reduced in cross section.


A bending operation that joins the interlocking edges of two separate metal sheets together by folding them over one another.

Shear Force

A force that attempts to cause the internal structure of a material to slide against itself.

Shear Strength

The ability of a material to resist forces that attempt to cause the internal structure of the material to slide against itself.

Shut Height

The shut height of an upright press is the distance from the top of the bed to the bottom of the slide with stroke down and adjustment up. The shut height must always be defined either from the top of the bed or from the top of the bolster. The shut height of a horizontal or inverted press, or of a press with adjustable bed, can be defined in a similar manner. Generally the shut height is equal to the maximum die-height of the die that can be accommodated, taking the bolster into consideration.

Slide / Ram

The most common name for the main reciprocating member of a press, guided in the press frame and to which the punch or upper die is fastened. It is also referred to as the ram. The inner slide of a double action press is called the plunger; the outer slide of a double action press is called the blank holder slide, and the slide of a hydraulic press is often called the platen.

Slide Adjustment

The distance a mechanical press slide can be moved from its maximum shut height to reduce  the die space height. The adjustment can be performed by hand or with a power mechanism.


An operation in which two or more parts are assembled permanently by upsetting a small portion of metal over the mating part, causing the compression on the assembled parts.


The process of forming sheet metal at room temperature with the use of dies and punches.

Straight-Side Press

A type of press with supporting columns in each corner of the frame suspending the crown over the bed. The straight-side press offers improved rigidity and reduced deflection.


The distance marked by the farthest ends of reciprocating vertical movement of the press ram.


Forming a metal by the rapid striking of a large number of successive blows. In the case of aircraft cable fittings, the fitting is rotated while the press blows are being struck.

Throat (gap)

The open space in a gap frame press back of the slide centerline. The depth of throat (gap) is the distance from the slide centerline back to the frame metal of the upright section.

Tie Rod

Four long rods, with threads and nuts on both ends, which hold the frame members of a straight side press together.  These rods are stretched to place the frame members under compressive load.


A secondary operation on drawn or formed parts, to remove excess metal on the flange or on axial length.

Turret Press

A type of press with an open frame and a turret containing multiple punches. Turret presses are mostly used to perform a variety of shearing operations, and they are typically numerically controlled.

Upper Die Shoe

The upper plate of a die set that secures the punch holder.