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An gineering drawing is a type of technical drawing that is used to convey information about an object. A common use is to specify the geometry necessary for the construction of a compont and is called a detail drawing. Usually, a number of drawings are necessary to completely specify ev a simple compont. The drawings are linked together by a master drawing or assembly drawing which gives the drawing numbers of the subsequt detailed componts, quantities required, construction materials and possibly 3D images that can be used to locate individual items. Although mostly consisting of pictographic represtations, abbreviations and symbols are used for brevity and additional textual explanations may also be provided to convey the necessary information.
Drawings typically contain multiple views of a compont, although additional scratch views may be added of details for further explanation. Only the information that is a requiremt is typically specified. Key information such as dimsions is usually only specified in one place on a drawing, avoiding redundancy and the possibility of inconsistcy. Suitable tolerances are giv for critical dimsions to allow the compont to be manufactured and function. More detailed production drawings may be produced based on the information giv in an gineering drawing. Drawings have an information box or title block containing who drew the drawing, who approved it, units of dimsions, meaning of views, the title of the drawing and the drawing number.
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Technical drawing has existed since ancit times. Complex technical drawings were made in raissance times, such as the drawings of Leonardo da Vinci. Modern gineering drawing, with its precise convtions of orthographic projection and scale, arose in France at a time wh the Industrial Revolution was in its infancy. L. T. C. Rolt's biography of Isambard Kingdom Brunel
Says of his father, Marc Isambard Brunel, that "It seems fairly certain that Marc's drawings of his block-making machinery (in 1799) made a contribution to British gineering technique much greater than the machines they represted. For it is safe to assume that he had mastered the art of presting three-dimsional objects in a two-dimsional plane which we now call mechanical drawing. It had be evolved by Gaspard Monge of Mezieres in 1765 but had remained a military secret until 1794 and was therefore unknown in gland."
Gineering drawings specify requiremts of a compont or assembly which can be complicated. Standards provide rules for their specification and interpretation. Standardization also aids internationalization, because people from differt countries who speak differt languages can read the same gineering drawing, and interpret it the same way.
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One major set of gineering drawing standards is ASME Y14.5 and Y14.5M (most rectly revised in 2009). These apply widely in the United States, although ISO 8015 (Geometrical product specifications (GPS) — Fundamtals — Concepts, principles and rules) is now also important. In 2018, ASME AED-1 was created to develop advanced practices unique to aerospace and other industries and supplemt to Y14.5 Standards.
In 2011, a new revision of ISO 8015 (Geometrical product specifications (GPS) — Fundamtals — Concepts, principles and rules) was published containing the Invocation Principle. This states that, "Once a portion of the ISO geometric product specification (GPS) system is invoked in a mechanical gineering product documtation, the tire ISO GPS system is invoked." It also goes on to state that marking a drawing "Tolerancing ISO 8015" is optional. The implication of this is that any drawing using ISO symbols can only be interpreted to ISO GPS rules. The only way not to invoke the ISO GPS system is to invoke a national or other standard. Britain, BS 8888 (Technical Product Specification) has undergone important updates in the 2010s.
For cturies, until the 1970s, all gineering drawing was done manually by using pcil and p on paper or other substrate (e.g., vellum, mylar). Since the advt of computer-aided design (CAD), gineering drawing has be done more and more in the electronic medium with each passing decade. Today most gineering drawing is done with CAD, but pcil and paper have not tirely disappeared.
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Some of the tools of manual drafting include pcils, ps and their ink, straightedges, T-squares, Frch curves, triangles, rulers, protractors, dividers, compasses, scales, erasers, and tacks or push pins. (Slide rules used to number among the supplies, too, but nowadays ev manual drafting, wh it occurs, befits from a pocket calculator or its onscre equivalt.) And of course the tools also include drawing boards (drafting boards) or tables. The glish idiom "to go back to the drawing board", which is a figurative phrase meaning to rethink something altogether, was inspired by the literal act of discovering design errors during production and returning to a drawing board to revise the gineering drawing. Drafting machines are devices that aid manual drafting by combining drawing boards, straightedges, pantographs, and other tools into one integrated drawing vironmt. CAD provides their virtual equivalts.
Producing drawings usually involves creating an original that is th reproduced, gerating multiple copies to be distributed to the shop floor, vdors, company archives, and so on. The classic reproduction methods involved blue and white appearances (whether white-on-blue or blue-on-white), which is why gineering drawings were long called, and ev today are still oft called, "blueprints" or "bluelines", ev though those terms are anachronistic from a literal perspective, since most copies of gineering drawings today are made by more modern methods (oft inkjet or laser printing) that yield black or multicolour lines on white paper. The more geric term "print" is now in common usage in the U.S. to mean any paper copy of an gineering drawing. In the case of CAD drawings, the original is the CAD file, and the printouts of that file are the "prints".
Almost all gineering drawings (except perhaps referce-only views or initial sketches) communicate not only geometry (shape and location) but also dimsions and tolerances
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For those characteristics. Several systems of dimsioning and tolerancing have evolved. The simplest dimsioning system just specifies distances betwe points (such as an object's lgth or width, or hole cter locations). Since the advt of well-developed interchangeable manufacture, these distances have be accompanied by tolerances of the plus-or-minus or min-and-max-limit types. Coordinate dimsioning involves defining all points, lines, planes, and profiles in terms of Cartesian coordinates, with a common origin. Coordinate dimsioning was the sole best option until the post-World War II era saw the developmt of geometric dimsioning and tolerancing (GD&T), which departs from the limitations of coordinate dimsioning (e.g., rectangular-only tolerance zones, tolerance stacking) to allow the most logical tolerancing of both geometry and dimsions (that is, both form [shapes/locations] and sizes).
In most cases, a single view is not sufficit to show all necessary features, and several views are used. Types of views include the following:
A multiview projection is a type of orthographic projection that shows the object as it looks from the front, right, left, top, bottom, or back (e.g. the primary views), and is typically positioned relative to each other according to the rules of either first-angle or third-angle projection. The origin and vector direction of the projectors (also called projection lines) differs, as explained below.
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But circa the 1890s, third-angle projection spread throughout the North American gineering and manufacturing communities to the point of becoming a widely followed convtion,
As shown above, the determination of what surface constitutes the front, back, top, and bottom varies depding on the projection method used.
But any combination of views may be used depding on the needs of the particular design. In addition to the six principal views (front, back, top, bottom, right side, left side), any auxiliary views or sections may be included as serve the purposes of part definition and its communication. View lines or section lines (lines with arrows marked "A-A", "B-B", etc.) define the direction and location of viewing or sectioning. Sometimes a note tells the reader in which zone(s) of the drawing to find the view or section.
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These views are typically used wh an object contains some sort of inclined plane. Using the auxiliary view allows for that inclined plane (and any other significant features) to be projected in their true size and shape. The true size and shape of any feature in an gineering drawing can only be known wh the Line of Sight (LOS) is perpdicular to the plane being referced. It is shown like a three-dimsional object. Auxiliary views td to make use of axonometric projection. Wh existing all by themselves, auxiliary views are sometimes known as pictorials.
An isometric projection shows the object from angles in which the scales along each axis of the object are equal. Isometric projection corresponds to rotation of the object by ± 45° about the vertical axis, followed by rotation of approximately ± 35.264° [= arcsin(tan(30°))] about the horizontal axis starting from an orthographic projection view. "Isometric" comes from the Greek for "same measure". One of the things that makes
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