ALUMINUM GLOSSARY - M

Machinability

The relative ease of working a metal with machine tools. Aluminum has good machinability.

Machining

The quantified removal of metal from the die using a cutting tool or erosion through the electrical discharge process.

Main Cylinder

The chamber of an extrusion press into which hydraulic fluid is pumped to generate the desired ram pressure and movement.

Mandrel

The fixed or floating projection positioned in the die opening that forces metal to flow around it. The wall thickness of the extrusion is determined by the difference in the dimensions of the die aperture and the mandrel.

Mark

Damage in the surface of the product whose name is often described by source.

Mark , Arbor

Surface damage in the vicinity of a coil ID caused by contact with a roughened, damaged or non-circular arbor or by the end of the product.

Mark , Bearing

A depression in the extruded surface caused by a change in bearing length in the extrusion die.

Mark , Carbon (Graphite)

Gray or black surface marking caused by contact with carbon runout blocks.

Mark , Chatter (roll or leveller)

Numerous intermittent lines or grooves that are usually full width and perpendicular to the rolling or extrusion direction.

Mark , Handling

(1) For rolled products, an area of broken surface that is introduced after processing. The mark usually has no relationship to the rolling direction. (2) For extrusions, damage that can be imparted to the surface during handling operations.

Mark , Rub

A large number of very fine scratches or abrasions. A rub mark can occur by metal-to-metal contact, movement in handling and movement in transit.

Mark , Stop

A bank-like pattern around the full perimeter of an extruded section and perpendicular to its length. A stop mark occurs whenever the extrusion process is suspended.

Mark , Stretcher Jaw

A cross hatched appearance left by jaws at the end(s) of metal that has been stretched. These marks are seen if insufficient metal has been removed after the stretching operation.

Mark , Traffic

Abrasion which results from relative movement between contacting metal surfaces during handling and transit. A dark color from the abrasively produced aluminum oxide is usually observed. A mirror image of a traffic mark is observed on the adjacent contacting surface.

Maximum Speed

The fastest practical extrusion rate or velocity which is related to the extrusion press ram's velocity. The formula is: Max. ram speed (ipm) x reduction ratio x 12 = maximum speed (ft/min).

Mechanical Properties

Those properties of a material that are associated with elastic and inelastic reaction when force is applied, or that involve the relationship between stress and strain; for example, modulus of elasticity, tensile strength, endurance limit. These properties are often incorrectly referred to as physical properties.

Mechanical Working

Subjecting metal to pressure exerted by rolls, dies, presses, or hammers to change its form or to affect its structure and its mechanical and physical properties.

Metal Dimension

Any dimension, through a part of an extruded cross-sectional shape, whose length includes at least 75 percent metal, versus open space.

Metal Entry

The location where the aluminum alloy enters the port opening of a hollow die or the initial opening of a solid die.

Metal Flow

The manner in which metal moves both in the container and through the extrusion die.

Mil

A unit of length; 0.001 inch.

Mild Steel

Steel with a maximum carbon content of about 0.25 percent.

Mill Finish

Mill finish is the finish obtained by standard extrusion practices and produced without the aid of any subsequent operations. This finish generally varies from a structural finish with surface imperfections to an architectural finish with uniformly good appearance.

Milling

Removing metal with a machine tool something like a rotary chisel.

Mini Insert Die

Small self-contained dies that fit into a housing.

Modulus of Elasticity

The ratio of stress to corresponding strain throughout the range where they are proportional. As there are three kinds of stresses, so there are three kinds of moduli of elasticity for any material -- modulus in tension, in compression, and in shear.

Multivoting

A technique used in the expression of opinions regarding several topics.