Engineering drawing abbreviations and symbols
Engineering drawing abbreviations and symbols are used to communicate and detail the characteristics of an engineering drawing. This list includes abbreviations common to the vocabulary of people who work with engineering drawings in the manufacture and inspection of parts and assemblies.
Technical standards exist to provide glossaries of abbreviations, acronyms, and symbols that may be found on engineering drawings. Many corporations have such standards, which define some terms and symbols specific to them; on the national and international level, ASME standard Y14.38 is one of the widely used standards.
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| Abbreviation or symbol | Definition | Description |
| ' | ||
| ' | ||
| across corners | Commonly used when measuring the corners of a hex drive, such as a hex nut. | |
| across flats | Commonly used when measuring the flat surfaces of a hex drive, such as a hex nut. | |
| AFF | above finished floor | A dimension that establishes a distance away from the finished floor. Example would be the top of a coffee table to the shag of the carpet, not where the bottom of the tables feet dig in. |
| American Iron and Steel Institute | The AISI acronym is commonly seen as a prefix to steel grades, for example, "AISI 4140". The SAE steel grade system was formerly a joint AISI-SAE system. | |
| or | aluminium | |
| alloy | ||
| American | Referring to the United States | |
| Aerospace Material Standards | Standards in materials science and engineering maintained by SAE International and widely used in the aerospace manufacturing industries. | |
| Army-Navy | A prefix for standard hardware [|ID] numbers. Came from the era of circa 1890s-1945, when the U.S. Army and Navy were leading the way on product standardization for logistics improvement, yielding the United States Military Standards system. Today industry and ISO also do a lot of this standardization specification, freeing the U.S. [|DOD] and military to do less of it, although many [|MIL standards] are still current. | |
| anneal, annealed | ||
| American National Standards Institute | And the many standards that it issues, for example, ANSI Z87.1. | |
| approximately | ||
| acceptable quality level | The threshold of defectiveness that is allowable in a group of parts. It is trivial to say that no one wants any error, and that everyone wants uniform perfection; but in the real world, it almost never happens. The intelligence behind defining AQLs is in figuring out how much error is tolerable given the costs that would be incurred by any efforts to further reduce its incidence. | |
| as required | An abbreviation used in parts lists in the quantity-per-assembly field when a discrete count is not applicable. For example, in an assembly with a bolted joint using four bolts, the PL quantity column will say "4" for the bolt PN, "4" for the nut PN, and "AR" for the liquid threadlocker that will be applied. | |
| Aerospace Standards; Australian Standards | 1. Aerospace Standards, technical standards maintained by SAE International and widely used in the aerospace manufacturing industries. Standard aerospace hardware sometimes has the AS- prefix in the catalog numbers. 2. Australian Standards, standards per Australian industry. | |
| AS, APS, APV, AV, APSL, AVL | approved product supplier, approved vendor, approved-product-supplier list, approved-vendor list | When only certain companies are approved by the [|CDA] to manufacture the product, they are called by names such as "approved supplier", "approved product supplier", "approved vendor", or "approved product vendor". The list of such companies is called an APSL, AVL, or similar names. Vetting the companies on this list requires the CDA to audit the companies, which incurs an overhead expense for the CDA. Therefore, smaller companies will often cite larger companies' lists in order to avoid the cost of duplicating the effort. |
| American Standards Association | Former name for ANSI. | |
| American Society of Mechanical Engineers | And the many standards that it issues, for example, ASME Y14.5. | |
| assembly | referring to an assembly of parts rather than just one part. | |
| Formerly the American Society for Testing and Materials; now ASTM International | Maintains technical standards, especially regarding materials science and engineering and metrology. | |
| average | ||
| American Wire Gauge | ||
| ' | ||
| basic dimension | A [|basic] dimension is one that is the theoretical value without any tolerance range. It does not serve as an acceptance criterion. It is thus similar in some respects to a reference dimension. The reason why a basic dimension does not carry a tolerance is that its actual value will fall wherever it is put by other features' actual values, where the latter features are the ones with tolerances defined. A common and simple example is hole location: If a hole's centerpoint location has a position tolerance, then the centerpoint's coordinates do not need separate tolerances applied to them. Thus they are instead given as basic dimensions. In modern practice basic dimensions have a rectangular box around them, or sometimes the word "BASIC". | |
| diameter | ||
| BHC | bolt hole circle | Same definition as the bolt circle diameter |
| button head cap screw | Like an [|SHCS] but with a button head. | |
| Brinell hardness number | ||
| or BOM | bill of materials | Also called a list of materials. Overlaps a lot in concept with a parts list. There is no consistently enforced distinction between an [|L/M], a [|BoM], or a [|P/L]. |
| BoP or BOP | bought out part | A part which is outsourced from an external supplier, or "bought out". |
| , B/P | blueprint | "per B/P" = "per drawing" |
| bronze | ||
| basic dimension | See [|basic dimension info above]. | |
| ' | ||
| computer-aided design, computer-aided drafting; Plating#Cadmium plating|cadmium | ||
| Commercial and Government Entity | A [|CAGE code] is a unique identifier to label an entity that is a CDA, [|ODA], or [|MFR] of the part defined by the drawing. One corporation can have many CAGE codes, as can one government, because each division, department, and site can have its own CAGE code. The same CAGE code can change owners over the years. For example, a CAGE code that formerly referred to a certain Martin Marietta site will now refer to Lockheed Martin at that same site. | |
| [|centre-to-centre]; on centres | Defines centre-to-centre distance of two features, such as two holes. | |
| cubic boron nitride | A material from which some cutter inserts are made. | |
| current design activity | The CDA is the entity that currently has design authority over the part design. It may be the entity who first designed the part, but today it is also likely to be a designated successor entity, owing to mergers and acquisitions activity ; contract letting ; privatization ; or patent licensing. | |
| CERT or cert | certification | For example, certification of metallurgical content and processes |
| CG | centerless ground, centerless grinding | |
| Defines the center of a circle or partial circle. | ||
| chamfer | ||
| chamfer | ||
| cast iron | No longer a commonly used abbreviation. Better to spell out for clarity. | |
| or ℄ | or ; class | 1. Center line, the central axis of a feature. 2. Class, for example, "paint per spec XYZ [|revision] C type 1 class 2" may be abbreviated as "paint per spec XYZ [|REV] C TY 1 CL 2" or even in some cases "paint per spec XYZ-C-1-2". |
| computer numerical control | ||
| controlled radius | Radius of an arc or circle, with no flats or reversals. This strict version of radius definition is specified in demanding applications when the form of the radius must be controlled more strictly than "just falling within the dimensional tolerance zone". It is poor engineering to specify a CR instead of an R simply on the theory of enforcing good workmanship. CR is for critical features whose performance truly requires near-perfect geometry. Like most such characteristics, its presence increases the price of the part, because it raises the costs of manufacturing and quality assurance. | |
| corrosion-resistant | Largely synonymous with stainless steel, unless specific grades, specs, and distinctions are made on the drawing. Some people treat [|CRES] as a subset of the stainless steels. | |
| cold rolled steel; on centres | Defines centre-to-centre distance of two features, such as two holes. | |
| C/T | Correlation / Tracking | |
| or | counterbore | |
| or | countersink | |
| carton | ||
| ' | ||
| depth, deep, down | Defines the depth of a feature. | |
| diameter | Diameter of a circle. In a feature control frame, the ⌀ symbol tells you that the tolerance zone for the geometric tolerance is cylindrical. Abbreviations for "diameter" include ⌀, DIA, and D. | |
| diameter; delta | Abbreviations for "diameter" include ⌀, DIA, and D. For delta usage, see for example "delta notes". | |
| diameter | Diameter of a circle. Abbreviations for "diameter" include ⌀, DIA, and D. | |
| ductile iron pipe | ||
| dimension, dimensioning | ||
| , do | ditto | Seen occasionally in older drawings instead of repeating a given dimension. |
| , DoD | Department of Defense | See also [|MOD]. |
| digital product definition | A synonym of [|MBD]. | |
| , dwg | drawing | Referring to the engineering drawing |
| ' | ||
| ED | edge distance | Drilled holes, and fasteners are commonly required to have a minimum edge distance. |
| , ECO, ECN | engineering order | An order from the engineering department overriding/superseding a detail on the drawing, which gets superseded with revised information. Also called by various other names, such as engineering change order, engineering change notice, drawing change notice, and so on. See also REV. |
| equal, equally | For example, "⌀10 4X EQL SPACED ON BC" means "drill four holes of 10mm diameter equally spaced around the." | |
| electrical rule check | ||
| existing | ||
| ' | ||
| f | finish | An italic f written on a line representing a surface was an old way of indicating that the surface was to be machined rather than left in the as-cast or as-forged state. The "f" came from "finish" in the sense of "machine finish" as opposed to raw stock/casting/forging. Later the ASA convened upon [|a letter V] touching the surface. Soon this evolved into the "check mark" sign with accompanying number that tells the reader a max roughness value for the machined finish, to be measured with a profilometer. |
| finish all over | A note telling the manufacturer that all surfaces of the part are to be machined. Not an obsolete usage, but not seen as commonly as it was decades ago; not least because parts that once would have been spot-faced castings are now likelier to be contoured from billet with CNC milling. But more importantly, best engineering practice today, reflecting design for manufacturability and avoidance of spurious cost drivers, is either to specify specific, quantifiable requirements for surfaces with specific needs, or to leave finish out of the part definition because it is not important to fit, function, or criticality. This same spirit is behind the shift in military standards from writing requirements about methods to writing them instead about performance, with the method to reach that goal being up to the ingenuity of the designer. | |
| feature control frame | The rectangular box that conveys geometric tolerances in GD&T. It typically tells you what sort of geometric condition, followed by what size the tolerance zone is, and finally which datums it relates to, the order of gaging against them, and what material condition applies to them. A diameter symbol tells you that the zone for the geometric tolerance is cylindrical. | |
| or F/D | field of the drawing | The field of the drawing, as opposed to other areas of it, such as the parts list, general notes, flagnotes, title block, rev block, bill of materials, or list of materials. Rationales for drawing changes that are noted in the rev block often use these abbreviations for brevity. |
| full indicator movement | See also [|TIR]. | |
| flag note, flagnote | A note that is called out in specific spots in the field of the drawing. It is numbered with a stylized flag symbol surrounding the number. A general note applies generally and is not called out with flags. | |
| FL | Floor Level | Floor Level of an existing or proposed building or concrete pad |
| flag note, flagnote; find number | 1. Flagnote: A flagnote is a note that is called out in specific spots in the field of the drawing. It is numbered with a stylized flag symbol surrounding the number. A general note applies generally and is not called out with flags. 2. Find number: "FN" meaning "find number" refers to the ordinal number that gives an ID tag to one of the constituents in a parts list. Thus "fasten using FN7" refers to a fastener that is "find number" 7 in the list. | |
| feature of size | A type of physical feature on a part. An [|FoS] is a feature that can have size associated with it, usually involving the opposition of two surfaces. Features of size in reality always have actual sizes and forms that differ from their theoretical size and form; the purpose of tolerancing is to define whether the difference is acceptable or not. Thus material condition A given geometric tolerance may be defined in relation to a certain FoS datum being at [|LMC] or at [|MMC]. | |
| far side | The drawing notations "near side" and "far side" tell the reader which side of the part a feature is on, in occasional contexts where that fact is not communicated using the rules of projection alone. Contexts of usage are rather limited. One example is hole locations; "3X AND 3X FAR SIDE" defines symmetrical groups of 3 holes on both sides of a part, without having to redefine equivalent hole center coordinates on two separate views, one for each group. This is not only a convenience for the designer but also a method of error prevention, because it provides a way to avoid forking geometric definition that ideally should be kept unforked to prevent discrepancies. For example, the groups defined above cannot accidentally become asymmetrically discrepant in a future revision by the revisor failing to revise both groups equally. Another example is part marking locations. An area for part identification marking can be circled on a top view but assigned to either the top or bottom of the part simply with a "near side" or "far side" notation—which obviates adding any otherwise-unneeded bottom view to the field of the drawing. | |
| Federal Stock/Supply Code for Manufacturers | An older name for "CAGE code". Also NSCM. | |
| FTG | fitting | |
| ' | ||
| gray cast iron | ||
| geometric dimensioning and tolerancing | A standardized language for defining and communicating dimensions and tolerances. | |
| general note | Most engineering drawings have a notes list, which includes both general notes and flag notes. | |
| ' | ||
| hardness, Brinell, tungsten tip | See Brinell scale. | |
| high-density polyethylene | ||
| hex head cap screw | ||
| hardness, Rockwell, A scale | See Rockwell scale. | |
| hardness, Rockwell, B scale | See Rockwell scale. | |
| hardness, Rockwell, C scale | See Rockwell scale. | |
| hot rolled steel | ||
| heat treat, heat treatment | ||
| or H/T or HT | hardened and tempered | A form of heat treatment in which the metal is first hardened and then tempered. Compare N&T. |
| ' | ||
| IAW | in accordance with | A common need in engineering drawings is to instruct the user to do activity X in accordance with technical standard Y. For example, "Weld all subassemblies IAW AWS XYZ.123" means "Weld all subassemblies in accordance with American Welding Society standard number XYZ.123". The word "per" is functionally equivalent to "IAW" in such contexts; thus "rivet all sheet metal per MIL-PRF-123456" or " IAW MIL-PRF-123456". Part of the motivation behind the choice of words "in accordance with" is that they do not allege that any particular activity is explicitly specified by standard XYZ.123 ; rather, these words merely instruct the user that whatever s/he does must not contradict the standard in any way. But this is a subtle connotative distinction, and "per" and "IAW" are denotatively equivalent. |
| inner diameter; identity, identification number | ||
| IED | Insufficient Edge Distance | Drilled holes commonly have a required minimum edge distance, if the inspection finds that the edge distance is below minimum, then commonly reported as having an IED condition. |
| International Organization for Standardization | And the many standards that it specifies, for example, ISO 10303 | |
| ' | ||
| ' | ||
| key | Drawing callouts marked "KEY" define "key characteristics" that are considered especially important for fit, function, safety, or other reasons. They are thus subjected to higher inspection sampling levels. | |
| , kpsi | kilopounds per square inch, that is, thousands of pounds per square inch | See discussion at synonym [|KSI]. |
| , ksi | kilopounds per square inch, that is, thousands of pounds per square inch | KSI, also abbreviated KPSI or kpsi, is a common non-SI measurement scale for ultimate tensile strength, that is, the number of units of tensile force that a material can endure per unit of cross-sectional area before breaking. In the SI system, the unit is the pascal ; or, equivalently to pascals, newtons per square metre. |
| ' | ||
| limited dimension drawing | An implementation of model-based definition that still uses a 2D drawing, but only containing critical information. All information missing from the drawing is to be pulled from a 3D model of the part or assembly. | |
| left-hand | Referring to handedness, such as the helix handedness of screw threads or the mirror-image handedness of a symmetrical pair of parts. | |
| or L/M | list of materials | Also called a bill of materials. Overlaps a lot in concept with a parts list. There is no consistently enforced distinction between an L/M, a BoM, or a P/L. |
| least material condition | A material condition in GD&T. Means that a feature of size is at the limit of its size tolerance in the direction that leaves the least material left on the part. Thus an internal feature of size at its biggest diameter, or an external feature of size at its smallest thickness. The GD&T symbol for LMC is a circled L. A given geometric tolerance may be defined in relation to a certain FoS datum being at LMC or at MMC. | |
| ' | ||
| machine; machined | ||
| major | As in major diameter, or major characteristic | |
| maximum | ||
| model-based definition | Definition of the part via a 3D CAD model rather than via a 2D engineering drawing. Drawings may be printed from the model for [|reference] use, but the model remains the governing legal instrument. | |
| measurement between pins | threads, splines, gears | |
| measurement between wires | threads, splines, gears | |
| or M/F | make from | When one part number is made from another, it means to take part A and machine some additional features into it, creating part B. The parts list or L/M, in the "material" field, will say "M/F PN 12345". |
| manufactured | ||
| manufacturing | ||
| manufacturer | May be the same entity as the CDA or ODA, or may not be. | |
| Military | A prefix for the names of various United States Military Standards and Specifications, for example, MIL-STD-*, MIL-SPEC-*, MIL-DTL-*, MIL-PRF-*, MIL-A-*, MIL-C-*, MIL-S-*, MIL-STD-1913, MIL-STD-1397. | |
| minimum; minutes; minor | ||
| maximum material condition | A material condition in GD&T. Means that a feature of size is at the limit of its size tolerance in the direction that leaves the most material left on the part. Thus an internal feature of size at its smallest diameter, or an external feature of size at its biggest thickness. The GD&T symbol for MMC is a circled M. A given geometric tolerance may be defined in relation to a certain FoS datum being at LMC or at MMC. | |
| , MoD | Ministry of Defence | See also DOD. |
| , MoP | measurement over pins | threads, splines, gears |
| , MoW | measurement over wires | threads, splines, gears |
| , MPA | megapascals | The common SI measurement scale for ultimate tensile strength, that is, the number of units of tensile force that a material can endure per unit of cross-sectional area before breaking. There is only one correct casing for the symbol, cap-M-cap-P-small-a, which, like any SI unit of measurement symbol, properly should be preserved even when surrounding text is styled in all caps. But it is not uncommon to see "MPA" through carelessness. Users are not confused regardless. In non-SI terms, the unit for UTS is the KSI, which see herein. |
| material review board | A committee that reviews some nonconforming materials which are submitted as potentially still usable/saleable. | |
| United States Military Standard| Military Standard | Standards established by the U.S. military and widely used in the aerospace manufacturing and other defense industries. Standard hardware sometimes uses the [|MS-] prefix in the catalog numbers. | |
| ' | ||
| National Aerospace Standards | Standards maintained by SAE International and widely used in the aerospace manufacturing industries. The "National" formerly implicitly referenced the USA, but today [|NAS] and other standards are used globally. Standard hardware for aerospace work sometimes uses the NAS- prefix in the catalog numbers. | |
| National Coarse; numerical control | The National Coarse series of pre-1949 corresponds today to the Unified National Coarse of the Unified Thread Standard. | |
| nonconforming material | This abbreviation is used in a machine shop when recording nonconformances. For example, "An NCM tag was tied to the scrap part." | |
| nonconformance report | A report listing nonconformances. Helps to analyze system weaknesses. | |
| not elsewhere classified; National Electrical Code | In the sense of "not elsewhere classified", the abbreviation is well-known within certain fields, but not others; to avoid confusion, spell out. The National Electrical Code is a standard for electrical work. | |
| National Extra Fine | The National Extra Fine series of pre-1949 corresponds today to the Unified National Extra Fine of the Unified Thread Standard. | |
| National Fine | The National Fine series of pre-1949 corresponds today to the Unified National Fine of the Unified Thread Standard. | |
| notes list | A list of notes that appears somewhere on the drawing, often in the upper left corner. | |
| nominal | ||
| or NORMD | normalized | referring to normalization, a stress-relieving heat treatment. See also [|HT TR]. |
| Naval Primary Standard | ||
| National Pipe Taper | A subset series of the Unified Thread Standard. | |
| National Special; [|near side] | 1. National Special, a screw thread series; see Unified Thread Standard. An extensible series, covering various special threads. 2. Near side: The drawing notations "near side" and "far side" tell the reader which side of the part a feature is on, in occasional contexts where that fact is not communicated using the rules of projection alone. Contexts of usage are rather limited. See "far side" for examples. | |
| National Stock/Supply Code for Manufacturers | An older name for "CAGE code". Also FSCM. | |
| or N/T or NT | normalized and tempered | A form of heat treatment in which the metal is first normalized and then tempered. Compare H&T. |
| not to scale | See also Engineering drawing > Scale. | |
| ' | ||
| overall length | ||
| on center | That is, centre-to-centre; defines centre-to-centre distance of two features, such as two holes. | |
| outer diameter | ||
| original design activity | The entity that originally designed a part. Compare to CDA, the entity that currently has design authority over the part design. | |
| over high limit | This abbreviation is used in a machine shop when recording nonconformances. For example, "part scrapped because ID is [|OHL]." See also [|ULL]. | |
| opposite | See Part number > Symmetrical parts for explanation. | |
| ORIG | original | |
| ' | ||
| piece, pieces | ||
| pitch diameter | ||
| , PDMS | product data management, product data manager , product data management system | A database and related application that facilitate all aspects of managing data files—e.g., TDPs, TDP versions, drawings, model datasets, specs, addenda, certs, memoranda, EOs, ECOs, DCNs, RFQs, quotes, POs, e-mails, faxes, photos, word processor documents, spreadsheets. See also [|PLM]. |
| or P/H | precipitation hardening, precipitation-hardened; pilot hole | |
| phosphor bronze | ||
| or P/L | parts list | A list, usually tabular and often on the drawing, listing the parts needed in an assembly, including subparts, standard parts, and hardware. There is no consistently enforced distinction between an L/M, a BoM, or a P/L. |
| product lifecycle management; plant lifecycle management | See also [|PDM]. | |
| PMI | Product and manufacturing information | Product and manufacturing information conveys non-geometric attributes in 3D computer-aided design and Collaborative Product Development systems necessary for manufacturing product components and assemblies. |
| or P/N | part number | |
| point of intersection | A point that makes easier the layout, toolpath programming, or inspection of the part. It is the intersection point of lines that may not meet on the finished part, such as the tangent lines of a curve or the theoretical sharp corner that edge-breaking and deburring will remove. See also [|SC], [|TSC], and [|AC]. | |
| P.F. | press fit | A fastening or mating between two parts which is achieved by friction after the parts are pushed together. |
| pounds per square inch | A unit of measurement for pressure. See also KSI. | |
| polytetrafluoroethylene | Also well known by the brand name Teflon. | |
| polyvinyl chloride | ||
| ' | ||
| quality management system | A system in place to ensure that quality of manufacture is produced and maintained; a system to prevent defective parts from being made, or, even if made, from getting into finished inventories. | |
| or qty | quantity | |
| ' | ||
| radius | Radius of an arc or circle. Flats and reversals are tolerated unless "CR" is explicitly specified. | |
| , Ra | roughness, average; Rockwell A scale | See surface roughness; see Rockwell scale. |
| , Rb | Rockwell B scale | See Rockwell scale. |
| , Rc | Rockwell C scale | See Rockwell scale. |
| or | reference | The dimension or note is given only for reference and thus is not to be used as a part acceptance criterion. The dimension may also be surrounded by parentheses to signify a reference dimension. When a dimension is defined in one view but also mentioned again in another view, it will be given as reference in the second case. This rule prevents the mistake of defining it in two different ways accidentally; the "main" mention is the only one that counts as a feature definition and thus as a part acceptance criterion. See also basic dimensions, which are similar in some respects. |
| or REQ'D | required | For example, "4 REQD" written next to a fastener means that four of those fasteners are required for the assembly. |
| revision | Engineering drawings and material or process specifications are often revised; the usual revision control convention is to label the versions A, B, C, D, etc.; a revision block is a tabular area on the drawing that lists the revision letters, a brief description of the changes and reasons, and approval initials and dates. Revisions beyond "Z" start the alphabet over again with doubling, e.g., AA, AB, AC, AD, and so on. In the days of manual drafting, redrawing was expensive, so engineering orders were not always incorporated into a next-letter revision. They thus accompany the drawing as part of the TDP. With the dissemination of software usage, revision control is often better handled nowadays, in competent hands at least. In recent years the revision control of engineering drawings has even been standardized by ASME, in their standard Y14.35M. | |
| regardless of feature size | A material condition in GD&T. Means that a given geometric tolerance is true in relation to a certain datum regardless of its actual size. | |
| right-hand | Referring to handedness, such as the helix handedness of screw threads or the mirror-image handedness of a symmetrical pair of parts. | |
| roughness height reading | See surface roughness. | |
| RL | Reduced Level or Relative Level | Surface Level |
| return material authorization | See also [|RTV]. | |
| root mean square | RMS in general is a statistical technique to define a representative value for a group of data points. With regard to surface roughness, it means that the heights of the individual microscopic peaks and valleys shall be averaged together via RMS to yield a measurement of roughness. See also herein f as a finish mark. | |
| or R/T | rough turn, rough turned; room temperature | Rough-turned means turned on a lathe but not finished to a final machined dimension and surface roughness. Can apply to bar stock or to parts in-process. Room temperature is sometimes abbreviated "RT" within tables of specs for finishing operations. |
| release to production | The issuance of a drawing from the engineering/design activity to the production activity. In other words, the event when a draft becomes a completed, official document. A stamp on the drawing saying "ISSUED" documents that RTP has occurred. | |
| room-temperature vulcanizing; return to vendor | 1. RTV sealants, a way to seal joints. 2. Return to vendor, send parts back to a vendor for rework or refund because they are nonconforming. Such RTV often requires an [|RMA]. | |
| , Rz | roughness, mean depth | See surface roughness. |
| ' | ||
| Formerly the Society of Automotive Engineers; now SAE International | And the many standards that it issues, for example, the SAE AMS and SAE AS standards series. | |
| or S/C | sharp corners | Dimensions may be given as "across sharp corners" although the corners get radiused. In other words, distances may be given from intersection points where lines intersect, regardless of edge breaks or fillets. This is usually implied by default, so "S/C" often need not be explicitly added. But in some cases it clarifies the definition. See also TSC, [|POI], and AC. |
| or S/F | spotface slip fit | |
| or S/FACE | spotface | |
| socket head cap screw | A cap screw with a socket head. | |
| or S/N | serial number | |
| solution anneal, solution annealed | ||
| specification | ||
| spheroidize anneal | ||
| Spot facing | ||
| spherical radius | Radius of a sphere or spherical segment. | |
| or S/S | stainless steel; supersede | 1. Stainless steel, see also CRES. 2. Supersede/supersedes/superseded, refers to when one document replaces another. |
| stainless steel | As per Y14.38–2007 | |
| standard | ||
| Standard for the Exchange of Product Model Data | A standard format defined by ISO 10303 for MBD data generation, storage, and exchange. | |
| solution treated and aged | ||
| screw thread insert | ||
| steel | ||
| stock | A nominal dimension for the stock material, such as bar stock | |
| Schlüsselweite | Translates as Key or Wrench Width. Width across flats, often found on drawings of german origin. | |
| ' | ||
| tapped hole | Usually implies drilling a hole if the hole does not already exist. | |
| title block | An area of the drawing, almost always at the bottom right, that contains the title of the drawing and other key information. Typical fields in the title block include the drawing title ; drawing number ; names and/or ID numbers relating to who designed and/or manufactures the part ; company name ; initials/signatures of the original draftsman ; initials/signatures of approving managers ; cross-references to other documents; default tolerancing values for dimensions, geometry, and surface roughness; raw-material info ; and access control information. [|Drawing revision] information is not always included in the title block because it often appears in a separate revisions block. | |
| technical data package | The complete package of information that defines a part, of which the drawing itself is often only a subset. It also includes engineering orders, 3D model datasets, data tables, memoranda, and any special conditions called out by the purchase order or the companies' terms-and-conditions documents. | |
| or thd | thread | |
| THRD | threaded | |
| or thk | thickness | |
| through | Optionally applied to a hole dimension to signify that the hole extends through the workpiece. For example, THRU may be stated in a hole dimension if the hole's end condition is not clear from graphical representation of the workpiece. | |
| Through all | Similar to THRU. Sometimes used on hole dimensions for clarity to denote that the hole extends through multiple open space features as it goes through the whole workpiece. | |
| total indicator reading; total indicated run-out | For measurements of eccentricity and other deviations from nominal geometry | |
| top of steel | ||
| tolerance, tolerancing | ||
| theoretical sharp corner | See discussion at SC and POI. | |
| type | For an explanation of "type" abbreviated as "TY", see the example given at [|"CL" meaning "class"]. | |
| Typical | Other features share the same characteristic. For example, if the drawing shows 8 holes on a bolt circle, and just one is dimensioned, with "TYP" or "" following the dimension label, it means that that hole is typical of all 8 holes; in other words, it means that the other 7 holes are that size also. The latest revisions of Y14.5 deprecate "TYP" by itself in favor of the specifying of a number of times, such as "2X" or "8X". This helps avoid any ambiguity or uncertainty. TYP or Typical was described in Mil-Std-8, the directing body prior to adoption of the dimension tolerance interpretation Y14.5 series. Its last revision was C in 1963, but can still be found in many older aircraft drawings. | |
| ' | ||
| use as-is | One of the possible [|MRB] dispositions. Others include scrap and rework. | |
| under low limit | This abbreviation is used in a machine shop when recording nonconformances. For example, "part scrapped because [|OD] is ULL." See also OHL. | |
| Unified National Coarse | A subset series of the Unified Thread Standard. | |
| Unified National Extra Fine | A subset series of the Unified Thread Standard. | |
| Unified National Fine | A subset series of the Unified Thread Standard. | |
| Unified National "J" series Coarse | A subset series of the Unified Thread Standard, with controlled root radius and increased minor diameter. For applications requiring maximum fatigue resistance amid chronic vibration. | |
| Unified National "J" series Fine | A subset series of the Unified Thread Standard, with controlled root radius and increased minor diameter. For applications requiring maximum fatigue resistance amid chronic vibration. | |
| unless noted otherwise | A fairly well-known abbreviation, but to avoid confusion, spell out. | |
| Unified National Special; unified numbering system | Unified National Special is a subset series of the Unified Thread Standard. It is an extensible series, covering various special threads. The unified numbering system is a vaguely named standard for naming alloys by principal element percentages. | |
| unless otherwise noted | A little-used abbreviation. To avoid confusion, spell out. | |
| unless otherwise specified | A fairly well-known abbreviation, but to avoid confusion, spell out. | |
| United States of America Standards Institute | Former name for ANSI. | |
| United States Standard; United States Steel | U.S. Standard threads became the National series, which became the Unified National series ; see Unified Thread Standard. As for U.S. Steel, it was once the largest steel company on earth, often an [|approved supplier], and not infrequently a sole source; hence its mention on drawings. | |
| ultimate tensile strength; Unified Thread Standard | ||
| ' | ||
| v | finish | A letter v written on a line representing a surface is a way to indicate that the surface is to be machined rather than left in the as-cast or as-forged state. The older symbol for this was a small script f. Later the ASA convened upon a letter V touching the surface. Soon this evolved into the "check mark" sign with accompanying number that tells the reader a max roughness value for the machined finish, to be measured with a profilometer. |
| ' | ||
| tungsten carbide | The "W" comes from the element symbol for tungsten, W, which comes from the German Wolfram. | |
| WI | wrought iron | Both the material and the abbreviation are obsolete, or nearly so. Spell out the words if this material is to be mentioned at all in modern drawings. |
| W/I, w/i | within | A little-used abbreviation. Better to spell out for clarity. |
| W/O, w/o | without | Better to spell out for clarity. |
| ' | ||
| used to indicate the word “by” | When the letter X is preceded by a space, this means "by". For example, a chamfer may be called out as 12 X 45° | |
| or | number of places—for example, 8X or | When a dimension is used in multiple places either of these prefixes can be added to the dimension to define how many times this dimension is used. This example signifies eight places. There should be no whitespace between the numeral and the letter X. the letter X and the multiplication sign |
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| — | Calls out the drawing standard that this drawing is following. For example, ASME Y14.5 and Y14.100 are commonly used standards that define all of the symbols and drafting conventions used. | |
| yield strength | ||
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