Air-lift hammer

A type of gravity-drop hammer in which the ram is raised for each stroke by an air cylinder. Because the length of stroke can be controlled, ram velocity and therefore the energy delivered to the workpiece can be varied. See also Drop Hammer and Gravity Hammer.

Aircraft quality

Denotes stock of sufficient quality to be forged into highly stressed parts for aircraft or other critical applications. Such materials are of extremely high quality, requiring closely controlled, restrictive practices in their manufacture in order that they may pass rigid requirements, such as magnetic particle inspection.

Alloy steel forging

One made from a steel containing additional alloying elements other than carbon (e.g., Ni, Cr, Mo) to enhance physical and mechanical properties and/or heat-treat response.


Aeronautical Materials Specification.

As forged

The condition of a forging as it comes out of the finisher cavity without any subsequent operations.

ASTM (Specifications)

The American Society for Testing and Materials.

Auxiliary operations

Additional processing steps performed on forgings to obtain properties, such as surface conditions or shapes, not obtained in the regular processing operation.

Axial rolls

In ring rolling, vertically displaceable, tapered rolls, mounted in a horizontally displaceable frame opposite from but on the same centerline as the main roll and rolling mandrel. The axial rolls control the ring height during the rolling process.

Axisymmetric forging

A forging where metal flow, during deformation, is predominately in a direction away from a common axis in a radial direction.

Backward extrusion

Forcing metal to flow in a direction opposite to the motion of a punch or die.


A section hot rolled from a billet to a form, such as round, hexagonal, octagonal, square, or rectangular, with sharp or rounded corners or edges, with a cross-sectional area of less than 16 sq in. (A solid section that is long in relation to its cross-sectional dimensions, having a completely symmetrical cross section and whose […]

Bar end

See End Loss.


Convexity of the surfaces of cylindrical or conical bodies, often produced unintentionally during upsetting or as a natural consequence during compression testing. See also Compression Test.

Batch/batch-type furnace

A furnace for heating materials where all loading and unloading is done through a single door or slot.

Bend or twist (defect)

Distortion similar to warpage, but resulting from different causes; generally caused in the forging or trimming operations. When the distortion is along the length of the part, it is called “bend”; when across the width, it is called “twist.”


A die impression, tool, or mechanical device designed to bend forging stock to conform to the general configuration of die impressions subsequently to be used.


A preliminary forging operation to give the piece approximately the correct shape for subsequent forming.


A semifinished, cogged, hot-rolled, or continuous-cast metal product of uniform section, usually rectangular with radiused corners. Billets are relatively larger than bars. See Bloom.


Amount of the die in contact with the workpiece throughout one entire forging reduction, e.g., heavy bite is three-quarter to full width of the die.


Raw material or forging stock (also called a “slug” or “multiple”) from which a forging is made.

Blast cleaning

A process for cleaning or finishing metal objects by use of an air jet or centrifugal wheel that propels abrasive particles (grit, sand, or shot) against the surfaces of the workpiece at high velocity.


The forging operation in which metal is progressively formed to general desired shape and contour by means of an impression die (used when only one block operation is scheduled).

Block and finish

The forging operation in which the part to be forged is blocked and finished in one heat through the use of a die having both a block impression and a finish impression in the same die. This also covers the case where two tools mounted in the same machine are used, as in the case […]

Block, first and second

Blocking operation performed in a die having two blocking cavities in the same die; the part being forged is successively blocked in each impression all in one heat. As many as three blocker dies are sometimes needed for some forgings and up to three operations are sometimes required in each die.

Block, first, second, and finish

The forging operation in which the part to be forged is passed in progressive order through three tools mounted in one forging machine; only one heat is involved for all three operations.