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Allowance (engineering)
In engineering and machining, an allowance is a planned deviation between an exact dimension and a Real versus nominal value, nominal or theoretical dimension, or between an intermediate-stage dimension and an intended final dimension. The unifying abstract concept is that a certain amount of difference ''allows for'' some known factor of compensation or interference. For example, an area of excess metal may be left because it is needed to complete subsequent machining. Common cases are listed below. An ''allowance,'' which is a ''planned'' deviation from an ideal, is contrasted with a ''Engineering tolerance, tolerance,'' which accounts for expected but unplanned deviations. Allowance is basically the size difference between components that work together. Allowance between parts that are assembled is very important. For example, the axle of a car has to be supported in a bearing otherwise it will fall to the ground. If there was no gap between the axle and the bearing then there w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Engineering
Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, systems. Modern engineering comprises many subfields which include designing and improving infrastructure, machinery, vehicles, electronics, Materials engineering, materials, and energy systems. The Academic discipline, discipline of engineering encompasses a broad range of more Academic specialization, specialized fields of engineering, each with a more specific emphasis for applications of applied mathematics, mathematics and applied science, science. See glossary of engineering. The word '':wikt:engineering, engineering'' is derived from the Latin . Definition The American Engineers' Council for Professional Development (the predecessor of the Accreditation Board for Engineering and Technology aka ABET) has defined "engineering" as: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Machining
Machining is a manufacturing process where a desired shape or part is created using the controlled removal of material, most often metal, from a larger piece of raw material by cutting. Machining is a form of subtractive manufacturing, which utilizes machine tools, in contrast to ''additive manufacturing'' (e.g. 3D printing processes, 3D printing), which uses controlled addition of material. Machining is a major process of the manufacture of many metal products, but it can also be used on other materials such as wood, plastic, ceramic, and composite material, composites. A person who specializes in machining is called a machinist. As a commercial venture, machining is generally performed in a machine shop, which consists of one or more workrooms containing primary machine tools. Although a machine shop can be a standalone operation, many businesses maintain internal machine shops or tool rooms that support their specialized needs. Much modern-day machining uses Numerical control, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Real Versus Nominal Value
The distinction between real value and nominal value occurs in many fields. From a philosophical viewpoint, nominal value represents an accepted condition, which is a goal or an approximation, as opposed to the real value, which is always present. Measurement In manufacturing, a ''nominal size'' or ''trade size'' is a size "in name only" used for identification. The nominal size may not match any dimension of the product, but within the domain of that product the nominal size may correspond to a large number of highly standardized dimensions and tolerances. Nominal sizes may be well-standardized across an industry, or may be proprietary to one manufacturer. Applying the nominal size across domains requires understanding of the size systems in both areas; for example, someone wishing to select a drill bit to clear a "-inch screw" may consult tables to show the proper drill bit size. Someone wishing to calculate the load capacity of a steel beam would have to consult tables to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theoretical
A theory is a systematic and rational form of abstract thinking about a phenomenon, or the conclusions derived from such thinking. It involves contemplative and logical reasoning, often supported by processes such as observation, experimentation, and research. Theories can be scientific, falling within the realm of empirical and testable knowledge, or they may belong to non-scientific disciplines, such as philosophy, art, or sociology. In some cases, theories may exist independently of any formal discipline. In modern science, the term "theory" refers to scientific theories, a well-confirmed type of explanation of nature, made in a way consistent with the scientific method, and fulfilling the criteria required by modern science. Such theories are described in such a way that scientific tests should be able to provide empirical support for it, or empirical contradiction (" falsify") of it. Scientific theories are the most reliable, rigorous, and comprehensive form of scientific k ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Engineering Tolerance
Engineering tolerance is the permissible limit or limits of variation in: # a physical dimension; # a measured value or physical property of a material, manufactured object, system, or service; # other measured values (such as temperature, humidity, etc.); # in engineering and safety, a physical distance or space (tolerance), as in a truck (lorry), train or boat under a bridge as well as a train in a tunnel (see structure gauge and loading gauge); # in mechanical engineering, the space between a bolt and a nut or a hole, etc. Dimensions, properties, or conditions may have some variation without significantly affecting functioning of systems, machines, structures, etc. A variation beyond the tolerance (for example, a temperature that is too hot or too cold) is said to be noncompliant, rejected, or exceeding the tolerance. Considerations when setting tolerances A primary concern is to determine how wide the tolerances may be without affecting other factors or the outcome of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grinding Machine
A grinding machine, often shortened to grinder, is any of various power tools or machine tools used for grinding. It is a type of material removal using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel's surface cuts a small chip from the workpiece via shear deformation. Grinding as a type of machining is used to finish workpieces that must show high surface quality (e.g., low surface roughness) and high accuracy of shape and dimension. As the accuracy in dimensions in grinding is of the order of 0.000025 mm, in most applications, it tends to be a finishing operation and removes comparatively little metal, about 0.25 to 0.50 mm depth. However, there are some roughing applications in which grinding removes high volumes of metal quite rapidly. Thus, grinding is a diverse field. Overview The grinding machine consists of a bed with a fixture to guide and hold the workpiece and a power-driven grinding wheel spinning at the required speed. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Treatment
Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve the desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering, carburizing, normalizing and quenching. Although the term ''heat treatment'' applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding. Physical processes Photomicrographs of steel. Top: In annealed (slowly cooled) steel, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reamer
A reamer is a type of rotary cutting tool used in metalworking. Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides. There are also non-precision reamers which are used for more basic enlargement of holes or for removing Burr (edge), burrs. The process of enlarging the hole is called reaming. There are many different types of reamer and they may be designed for use as a hand tool or in a machine tool, such as a milling machine or drill press. Construction A typical reamer consists of a set of Parallel (geometry), parallel straight or helical cutting edges along the length of a Cylinder (geometry), cylindrical body. Each cutting edge is ground at a slight angle and with a slight undercut below the cutting edge. Reamers must combine both hardness in the cutting edges, for long life, and toughness, so that the tool does not fail under the normal forces of use. They should only be use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interference Fit
An interference fit, also known as a pressed fit or friction fit, is a form of fastening between two tightfitting mating parts that produces a joint which is held together by friction after the parts are pushed together. Depending on the amount of interference, parts may be joined using a tap from a hammer or forced together using a hydraulic press. Critical components that must not sustain damage during joining may also be cooled significantly below room temperature to shrink one of the components before fitting. This method allows the components to be joined without force and produces a shrink fit interference when the component returns to normal temperature. Interference fits are commonly used with aircraft fasteners to improve the fatigue life of a joint. These fits, though applicable to shaft and hole assembly, are more often used for bearing-housing or bearing-shaft assembly. This is referred to as a 'press-in' mounting. Tightness of fit The tightness of fit is contr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microbially Influenced Corrosion
Microbial corrosion, also known as microbiologically influenced corrosion (MIC), microbially induced corrosion (MIC) or biocorrosion, occurs when microbes affect the electrochemical environment of the surface on which they are fixed. This usually involves the formation of a biofilm, which can either increase the corrosion of the surface or, in a process called microbial corrosion inhibition, protect the surface from corrosion. As every surface exposed to the environment is in some way also exposed to microbes, microbial corrosion causes trillions of dollars in damage around the globe annually. Microbes can locally create hypoxic conditions at the metal surface under a biofilm and contribute to the formation of anodic (oxidation) and cathodic ( reduction) sites initiating electrochemical potential differences and electrochemical corrosion. They can also act by either releasing byproducts from their cellular metabolism that corrode metals, or preventing normal corrosion inhibitors ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maximum Material Condition
Geometric dimensioning and tolerancing (GD&T) is a system for defining and communicating engineering tolerances via a Symbolic language (engineering), symbolic language on engineering drawings and computer-generated Solid modeling, 3D models that describes a physical object's nominal geometry and the permissible variation thereof. GD&T is used to define the nominal (theoretically perfect) geometry of parts and assemblies, the allowable variation in size, form, orientation, and location of individual features, and how features may vary in relation to one another such that a component is considered satisfactory for its intended use. Dimensional specifications define the nominal, as-modeled or as-intended geometry, while tolerance specifications define the allowable physical variation of individual features of a part or assembly. There are several standards available worldwide that describe the symbols and define the rules used in GD&T. One such standard is American Society of Mecha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grinding Machine
A grinding machine, often shortened to grinder, is any of various power tools or machine tools used for grinding. It is a type of material removal using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel's surface cuts a small chip from the workpiece via shear deformation. Grinding as a type of machining is used to finish workpieces that must show high surface quality (e.g., low surface roughness) and high accuracy of shape and dimension. As the accuracy in dimensions in grinding is of the order of 0.000025 mm, in most applications, it tends to be a finishing operation and removes comparatively little metal, about 0.25 to 0.50 mm depth. However, there are some roughing applications in which grinding removes high volumes of metal quite rapidly. Thus, grinding is a diverse field. Overview The grinding machine consists of a bed with a fixture to guide and hold the workpiece and a power-driven grinding wheel spinning at the required speed. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
