Drill rod

Bar stock, also colloquially known as billet, is a common form of raw purified metal, used by industry to manufacture metal parts and products.

Most metal produced by a steel mill or aluminium plant is formed (via rolling or extrusion) into long continuous strips of various size and shape. These strips are cut at regular intervals and allowed to cool, each segment becoming a piece of bar stock. A good analogy is pasta-making, in which lumps of dough are extruded into various cross-sectional shapes; cut into lengths; and then dried in that form. The cross-sectional shapes of pasta vary from simple bar or tube shapes (such as linguine or penne) to more elaborate extrusions (such as rotelle, fiori, or rotini). The same is true of metal bar stock. The most common shapes are round bar (also called rod), rectangular bar (including square bar, the special case of equal sides), and hexagonal bar (usually called hex bar for short). Tube and pipe are similar, but have hollow centers and are traditionally not called "bar" in industrial usage. (However, a product called hollow bar, essentially tube but with custom-orderable OD and ID and thus custom wall thickness, is marketed for lathe bar work which can benefit from obviation of drilling and rough boring.) Also similar in concept, but not called "bar", are the common structural shapes such as angle stock and channel stock. These are commonly available in steel and aluminum; the names "angle iron" and "channel iron" are still commonly used (informally) even though their literal namesake, wrought iron, has been replaced by steel and aluminum for most uses.

In a machine shop, bar stock and plate are often called billet, although in a rolling mill, that word refers to a piece of metal that has not yet been rolled into bar.

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