A workpiece is a piece, often made of a single material, that is being processed into another desired shape (such as building blocks).
The workpiece is usually a piece of relatively rigid material such as wood, metal, plastic, or stone. After a processing step, the workpiece may be moved on to further steps of processing. For example, a part can made out of bar stock and later become part of a semi-finished product.
A machine tool is a machine for handling or machining metal or other rigid materials, usually by cutting, boring, grinding, shearing, or other forms of deformations. Machine tools employ some sort of tool that does the cutting or shaping. All machine tools have some means of constraining the workpiece and provide a guided movement of the parts of the machine. Thus, the relative movement between the workpiece and the cutting tool (which is called the toolpath) is controlled or constrained by the machine to at least some extent, rather than being entirely "offhand" or "freehand". It is a power-driven metal cutting machine which assists in managing the needed relative motion between cutting tool and the job that changes the size and shape of the job material.
The precise definition of the term machine tool varies among users. While all machine tools are "machines that help people to make things", not all factory machines are machine tools.
A lathe (/leɪð/) is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, knurling, drilling, deformation, facing, threading and turning, with tools that are applied to the workpiece to create an object with symmetry about that axis.
Lathes are used in woodturning, metalworking, metal spinning, thermal spraying, reclamation, and glass-working. Lathes can be used to shape pottery, the best-known such design being the potter's wheel. Most suitably equipped metalworking lathes can be used to produce most solids of revolution, plane surfaces, and screw threads or helices. Ornamental lathes can produce more complex three-dimensional solids. The workpiece is usually held in place by either one or two centers, at least one of which can typically be moved horizontally to accommodate varying workpiece lengths. Other work-holding methods include clamping the work about the axis of rotation using a chuck or collet, or attaching it to a faceplate using clamps or dog clutch. Lathes equipped with special lathe milling fixtures can be used to complete milling operations.
Fusion welding is a generic term for welding processes that rely on melting to join materials of similar compositions and melting points. Due to the high-temperature phase transitions inherent to these processes, a heat-affected zone is created in the material (although some techniques, like beam welding, often minimize this effect by introducing comparatively little heat into the workpiece).
In contrast to fusion welding, solid-state welding does not involve the melting of materials.
A burr is a raised edge or small piece of material that remains attached to a workpiece after a modification process. It is usually an unwanted piece of material and is removed with a deburring tool in a process called deburring. Burrs are most commonly created by machining operations, such as grinding, drilling, milling, engraving or turning. It may be present in the form of a fine wire on the edge of a freshly sharpened tool or as a raised portion of a surface; this type of burr is commonly formed when a hammer strikes a surface. Deburring accounts for a significant portion of manufacturing costs.
In the printmaking technique of drypoint, burr, which gives a rich fuzzy quality to the engraved line, is highly desirable—the great problem with the drypoint medium is that the burr rapidly diminishes after as few as ten impressions are printed.
In machining, facing is the cutting of a flat surface perpendicular to some axis of the workpiece. This can be applied in two different areas:
Other operations remove material in ways similar to facing, for example, planing, shaping, and grinding, but these processes are not labeled by the term "facing."
A collet /ˈkɒlɪt/ is a segmented sleeve, band or collar. One of the two radial surfaces of a collet is usually tapered (i.e a truncated cone) and the other is cylindrical. The term collet commonly refers to a type of chuck that uses collets to hold either a workpiece or a tool (such as a drill), but collets have other mechanical applications.
An external collet is a sleeve with a cylindrical inner surface and a conical outer surface. The collet can be squeezed against a matching taper such that its inner surface contracts to a slightly smaller diameter, squeezing the tool or workpiece to hold it securely. Most often the collet is made of spring steel, with one or more kerf cuts along its length to allow it to expand and contract. This type of collet holds the external surface of the tool or workpiece being clamped. This is the most usual type of collet chuck. An external collet clamps against the internal surface or bore of a hollow cylinder. The collet's taper is internal and the collet expands when a corresponding taper is drawn or forced into the collet's internal taper.
A lathe faceplate is a basic workholding accessory for a wood or metal turning lathe. It is a circular metal (usually cast iron) plate which fixes to the end of the lathe spindle. The workpiece is then clamped to the faceplate, typically using t-slot nuts in slots in the faceplate, or less commonly threaded holes in the faceplate itself.
The faceplate may be attached to the lathe in several ways: the two most common are a thread and a precision cone arrangement, and threaded studs and a circular recess fitting a flange on the end of the spindle. Increasingly common is the camlock arrangement, in which shaped studs and cams replace threaded studs for rapid exchanging of the faceplate with other accessories, such as three or four jaw chucks.
Milling is the process of machining using rotary cutters to remove material by advancing a cutter into a workpiece. This may be done by varying directions on one or several axes, cutter head speed, and pressure. Milling covers a wide variety of different operations and machines, on scales from small individual parts to large, heavy-duty gang milling operations. It is one of the most commonly used processes for machining custom parts to precise tolerances.
Milling can be done with a wide range of machine tools. The original class of machine tools for milling was the milling machine (often called a mill). After the advent of computer numerical control (CNC) in the 1960s, milling machines evolved into machining centers: milling machines augmented by automatic tool changers, tool magazines or carousels, CNC capability, coolant systems, and enclosures. Milling centers are generally classified as vertical machining centers (VMCs) or horizontal machining centers (HMCs).
Honing is an abrasive machining process that produces a precision surface on a metal workpiece by scrubbing an abrasive grinding stone or grinding wheel against it along a controlled path. Honing is primarily used to improve the geometric form of a surface, but can also improve the surface finish.
Typical applications are the finishing of cylinders for internal combustion engines, air bearing spindles and gears. There are many types of hones, but all consist of one or more abrasive stones that are held under pressure against the surface they are working on.