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[1] is one of the widely used standards.
| Abbreviation or symbol | Definition | Description |
|---|
| {{Visible anchor>0-9}} | | |
| {{Visible anchor>A}} | | |
| {{Visible anchor|AC}} | across corners | Commonly used when measuring the corners of a hex drive, such as a hex nut. |
| {{Visible anchor|AF}} | 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. |
| {{Visible anchor|AISI}} | 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. |
| {{Visible anchor|Al}} or {{Visible anchor|AL}} | aluminium |
| {{Visible anchor|ALY}} | alloy |
| {{Visible anchor|AMER}} | American | Referring to the United States |
| {{Visible anchor|AMS}} | Aerospace Material Standards | Standards in materials science and engineering maintained by SAE International and widely used in the aerospace manufacturing industries. |
| {{Visible anchor|AN-}} | Army-Navy | A prefix for standard hardware (catalog 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 (as explained at United States Military Standard > Origins and evolution), although many MIL standards are still current. (See also MS- and NAS.) |
| {{Visible anchor|ANN}} | anneal, annealed |
| {{Visible anchor|ANSI}} | American National Standards Institute | And the many standards that it issues, for example, ANSI Z87.1. |
| {{Visible anchor|APPROX}}[2] | approximately |
| {{Visible anchor|AQL}} | 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. |
| {{Visible anchor|AR}} | as required | An abbreviation used in parts lists (PLs, LMs, BoMs) 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. |
| {{Visible anchor|AS}} | 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. |
| {{Anchor|approved suppliers abbreviations}} 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 (that is, to make what the drawing depicts/defines), they are called by names such as "approved supplier", "approved product supplier", "approved vendor", or "approved product vendor". The list of such companies (which usually changes over time) is called an APSL, AVL, or similar names. Vetting the companies on this list requires the CDA to audit (and possibly periodically re-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. |
| {{Visible anchor|ASA}} | American Standards Association | Former name for ANSI (1920s-1960s). |
| {{Visible anchor|ASME}} | American Society of Mechanical Engineers | And the many standards that it issues, for example, ASME Y14.5. |
| {{Visible anchor|ASSY or ASY}} | assembly | referring to an assembly of parts rather than just one (sub)part ("piece part", "detail part"). |
| {{Visible anchor|ASTM}} | Formerly the American Society for Testing and Materials; now ASTM International | Maintains technical standards, especially regarding materials science and engineering and metrology. |
| {{Visible anchor|AVG}} | average |
| {{Visible anchor|AWG}} | American Wire Gauge |
| {{Visible anchor>B}} | | |
| {{Visible anchor|BASIC}} | 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 (acceptably) 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 (and should not have) 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". |
| {{Visible anchor|BC or B.C.}} | bolt circle |
| {{Visible anchor|BCD or B.C.D.}} | bolt circle diameter |
| {{Visible anchor|BHCS}} | button head cap screw | Like an SHCS but with a button head. |
| {{Visible anchor|BHN}} | Brinell hardness number |
| {{Visible anchor|BoM}} or BOM | bill of materials | Also called a list of materials (LM or L/M). Overlaps a lot in concept with a parts list (PL or P/L). 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". |
| {{Visible anchor|BP}}, B/P | blueprint | "per B/P" = "per drawing" |
| {{Visible anchor|BRZ}} | bronze |
| {{Visible anchor|BSC}} | basic dimension | See basic dimension info above. |
| {{Visible anchor>C}} | | |
| {{Visible anchor|CAD}} | computer-aided design, computer-aided drafting; cadmium [plating] |
| {{Visible anchor|CAGE}} | Commercial and Government Entity [code] | A CAGE code is a unique identifier to label an entity (that is, a specific government agency or corporation at a specific site) 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 (campus) 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 (although the buildings may have been replaced and the signage may say different names). |
| {{Visible anchor|C-C or C-TO-C}} | centre-to-centre; on centres | Defines centre-to-centre distance of two features, such as two holes. |
| {{Visible anchor|CBN}} | cubic boron nitride | A material from which some cutter inserts are made. |
| {{Visible anchor|CDA}} | current design activity | The CDA is the entity (whether it be a corporation, a unit of a national military or ministry of defence, or another civilian government agency) that currently has design authority over the part design (definition). It may be the entity who first designed the part (that is, the ODA), but today it is also likely to be a designated successor entity, owing to mergers and acquisitions (M&A) activity (e.g., ODA company was bought by CDA company); contract letting (e.g., an Army engineering department ODA turns over the design activity to the prime contractor that makes most or all of the parts, turning that contractor into the new CDA); privatization (e.g., a government privatizes the design and manufacture of materiel, and a state arsenal [state armory] ODA transfers design authority to a private armory [defense contractor] ODA); or patent licensing (e.g., a patent-holding inventor [ODA] licenses one or several companies to manufacture products using his intellectual property, in which case the "same" part could end up with multiple design authorities, although they may not be considered the official/nominal CDA). |
| CERT or cert | certification | For example, certification of metallurgical content and processes |
| CG | centerless ground, centerless grinding |
| Center mark | Defines the center of a circle or partial circle. |
| {{Visible anchor|CH}} | chamfer |
| {{Visible anchor|CHAM}} | chamfer |
| {{Visible anchor|CI}} | cast iron | No longer a commonly used abbreviation. Better to spell out for clarity. |
| {{Visible anchor|CL}} or ℄ | centreline or centerline; 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". (The latter practice is not uncommon but is cryptic for workers with minimal training and experience. The first two options are better practice.) |
| {{Visible anchor|CNC}} | computer numerical control |
| {{Visible anchor|CR}} | 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. |
| {{Visible anchor|CRES}} | corrosion-resistant [steel] | 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. |
| {{Visible anchor|CRS}} | cold rolled steel; on centres | Defines centre-to-centre distance of two features, such as two holes. |
| C/T | Correlation / Tracking |
| {{Visible anchor|C'BORE or CBORE}} or | counterbore |
| {{Visible anchor|CSK or CSINK}} or | countersink |
| {{Visible anchor|CTN, ctn}} | carton |
| {{Visible anchor>D}} | | |
| depth, deep, down | Defines the depth of a feature. |
| {{Visible anchor|⌀}}[2] | diameter | Diameter of a circle. In a feature control frame (FCF), the ⌀ symbol tells you that the tolerance zone for the geometric tolerance is cylindrical. Abbreviations for "diameter" include ⌀, DIA, and D. |
| {{Visible anchor|D}} | diameter; delta | Abbreviations for "diameter" include ⌀, DIA, and D. For delta usage, see for example "delta notes". |
| {{Visible anchor|DIA}}[2] | diameter | Diameter of a circle. Abbreviations for "diameter" include ⌀, DIA, and D. |
| {{Visible anchor|DIP}} | ductile iron pipe |
| {{Visible anchor|DIM}} | dimension, dimensioning |
| {{Visible anchor|DO}}, do | ditto | Seen occasionally in older drawings instead of repeating a given dimension. |
| {{Visible anchor|DOD}}, DoD | [U.S.] Department of Defense | See also MOD. |
| {{Visible anchor|DPD}} | digital product definition | A synonym of MBD. |
| {{Visible anchor|DWG}}, dwg | drawing | Referring to the engineering drawing |
| {{Visible anchor>E}} | | |
| ED | edge distance | Drilled holes, and fasteners are commonly required to have a minimum edge distance (min ED). |
| {{Visible anchor|EO}}, ECO, ECN | engineering order | An order from the engineering department (to be followed by the production department or vendor) overriding/superseding a detail on the drawing, which gets superseded with revised information. Also called by various other names, such as engineering change order (ECO), engineering change notice (ECN), drawing change notice (DCN), and so on. See also REV. |
| {{Visible anchor|EQ}} | equal, equally | For example, "⌀10 4X EQ SPACED ON BC" means "drill four holes of 10mm diameter equally spaced around the bolt circle." |
| {{Visible anchor|ERC}} | electrical rule check | |
| {{Visible anchor>F}} | | |
| {{Anchor|f_meaning_finish}} f | finish | An italic f (Latin small letter 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 (specifically a sans-serif V) touching the surface. Soon this evolved into the "check mark" sign with accompanying number that tells the reader a max roughness value (RMS, microinches or micrometres) for the machined finish, to be measured with a profilometer. |
| {{Visible anchor|FAO}} | finish all over | A note telling the manufacturer that all surfaces of the part are to be machined (as opposed to leaving any surfaces as-cast or as-forged). 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 (such as RMS roughness measurements in microinches or micrometres, plus any plating or painting needs), or to leave finish out of the part definition (and thus at the manufacturer's discretion) 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. |
| {{Visible anchor|FCF}} | feature control frame | The rectangular box (with several cells) that conveys geometric tolerances in GD&T. It typically tells you what sort of geometric condition (e.g., parallel, perpendicular, round, concentric), followed by what size (and maybe shape) the tolerance zone is, and finally which datums it relates to, the order of gaging against them, and what material condition applies to them (LMC, MMC, or RFS). A diameter symbol (⌀) tells you that the zone for the geometric tolerance is cylindrical. |
| {{Visible anchor|FD}} or F/D | field of the drawing | The [main] field of the drawing, as opposed to other areas of it, such as the parts list (P/L), general notes (G/N), flagnotes (F/N or FL), title block (T/B), rev block (R/B), bill of materials (B/M or BoM or BOM), or list of materials (L/M). Rationales for drawing changes that are noted in the rev block often use these abbreviations for brevity (e.g., "DIM 14.00 was 12.50; added default TOL info to T/B; added leader lines to F/D; added alternate hardware IDs to P/L; added alternate alloy to L/M"). |
| {{Visible anchor|FIM}} | full indicator movement | See also TIR. |
| {{Visible anchor|FL}} | 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 |
| {{Visible anchor|FN or F/N}} | 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 (or sometimes a delta symbol). 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 (list of materials, bill of materials). Thus "fasten using FN7" refers to a fastener that is "find number" 7 in the list. |
| {{Visible anchor|FoS}} | 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 (e.g., the two diametrically opposite sides of a hole wall; the two opposite walls of a slot or flange). Features of size (FoSs) 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 (LMC, MMC, somewhere in between, or RFS) is important in GD&T. ) A given geometric tolerance may be defined in relation to a certain FoS datum being at LMC or at MMC. |
| {{Visible anchor|FS}} | 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 (6 total), 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 (because their definition is unified in only one place). 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. |
| {{Visible anchor|FSCM}} | Federal Stock/Supply Code for Manufacturers | An older name for "CAGE code". Also NSCM (National Stock/Supply Code for Manufacturers). |
| FTG | fitting |
| {{Visible anchor>G}} | | |
| {{Visible anchor|GCI}} | gray cast iron | |
| {{Visible anchor|GD&T or GDT}} | geometric dimensioning and tolerancing | A standardized language for defining and communicating dimensions and tolerances. |
| {{Visible anchor|GN or G/N}} | general note(s) | Most engineering drawings have a notes list, which includes both general notes and flag notes. |
| {{Visible anchor>H}} | | |
| {{Visible anchor|HBW}} | hardness, Brinell, tungsten tip | See Brinell scale. (The "W" comes from the element symbol for tungsten, W, which comes from the German Wolfram.) |
| {{Visible anchor|HDPE}} | high density polyethelene |
| {{Visible anchor|HHCS}} | hex head cap screw | |
| {{Visible anchor|HRA}} | hardness, Rockwell, A scale | See Rockwell scale. |
| {{Visible anchor|HRB}} | hardness, Rockwell, B scale | See Rockwell scale. |
| {{Visible anchor|HRC}} | hardness, Rockwell, C scale | See Rockwell scale. |
| {{Visible anchor|HRS}} | hot rolled steel |
| {{Visible anchor|HT TR}} | heat treat, heat treatment |
| {{Visible anchor|H&T}} 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. |
| {{Visible anchor>I}} | | |
| 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 number is hypothetical in this example). 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 (which "per" could be interpreted as alleging, at least in connotation); 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. |
| {{Visible anchor|ID}} | 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. |
| {{Visible anchor|ISO}} | International Organization for Standardization | And the many standards that it specifies, for example, ISO 10303 |
| {{Visible anchor>J}} | | |
| {{Visible anchor>K}} | | |
| {{Visible anchor|KEY}} | 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. |
| {{Visible anchor|KPSI}}, kpsi | kilopounds per square inch, that is, thousands of pounds per square inch | See discussion at synonym KSI. |
| {{Visible anchor|KSI}}, ksi | kilopounds per square inch, that is, thousands of pounds per square inch | KSI (or 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 (Pa) (or a multiple thereof, often megapascals (MPa), using the mega- prefix); or, equivalently to pascals, newtons per square metre (N/m²). |
| {{Visible anchor>L}} | | |
| {{Visible anchor|LDD}} | 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. |
| {{Visible anchor|LH}} | left-hand | Referring to handedness, such as the helix handedness of screw threads or the mirror-image handedness of a symmetrical pair of parts. |
| {{Visible anchor|LM}} or L/M | list of materials | Also called a bill of materials (BoM, BOM). Overlaps a lot in concept with a parts list (PL or P/L). There is no consistently enforced distinction between an L/M, a BoM, or a P/L. |
| {{Visible anchor|LMC}} | least material condition | A material condition in GD&T. Means that a feature of size (FoS) 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 (e.g., a hole) at its biggest diameter, or an external feature of size (e.g., a flange) at its smallest thickness. The GD&T symbol for LMC is a circled L. (See also MMC and RFS.) A given geometric tolerance may be defined in relation to a certain FoS datum being at LMC or at MMC. |
| {{Visible anchor>M}} | | |
| {{Visible anchor|MACH}} | machine; machined |
| {{Visible anchor|MAJ}} | major | As in major diameter, or major characteristic (for sampling level) |
| {{Visible anchor|MAX}}[2] | maximum |
| {{Visible anchor|MBD}} | model-based definition | Definition of the part via a 3D CAD model rather than via a 2D engineering drawing. Drawings may be printed (plotted) from the model for reference use, but the model remains the governing legal instrument. |
| {{Visible anchor|MBP}} | measurement between pins | threads, splines, gears (internal, female) (synonymous with MBW) (see also MOP, MOW) |
| {{Visible anchor|MBW}} | measurement between wires | threads, splines, gears (internal, female) (see also MBP, MOP, MOW) |
| {{Visible anchor|MF}} 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". |
| {{Visible anchor|MFD}} | manufactured |
| {{Visible anchor|MFG}} | manufacturing |
| {{Visible anchor|MFR}} | manufacturer | May be the same entity as the CDA or ODA, or may not be. |
| {{Visible anchor|MIL-}} | [U.S.] 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. |
| {{Visible anchor|MIN}}[2] | minimum; minutes; minor |
| {{Visible anchor|MMC}} | maximum material condition | A material condition in GD&T. Means that a feature of size (FoS) 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 (e.g., a hole) at its smallest diameter, or an external feature of size (e.g., a flange) at its biggest thickness. The GD&T symbol for MMC is a circled M. (See also LMC and RFS.) A given geometric tolerance may be defined in relation to a certain FoS datum being at LMC or at MMC. |
| {{Visible anchor|MOD}}, MoD | Ministry of Defence [U.K. and others] | See also DOD. |
| {{Visible anchor|MOP}}, MoP | measurement over pins | threads, splines, gears (external, male) (synonymous with MOW, measurement over wires) |
| {{Visible anchor|MOW}}, MoW | measurement over wires | threads, splines, gears (external, male) (see also MBW, MBP, MOP) |
| {{Visible anchor|MPa}}, MPA | megapascals | The common SI measurement scale for ultimate tensile strength (UTS), 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 (which latter is a frequently employed tradition in engineering drawing). 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 (or ksi), which see herein. |
| {{Visible anchor|MRB}} | material review board | A committee that reviews some nonconforming materials which are submitted as potentially still usable/saleable (if the nonconformance does not hinder fit or function). |
| {{Visible anchor|MS-}} | [U.S.] Military Standard | Standards established by the U.S. military and widely used in the aerospace manufacturing (military and civil) and other defense industries. Standard hardware sometimes uses the MS- prefix in the catalog numbers. (See also AN- and NAS.) |
| {{Visible anchor>N}} | | |
| {{Visible anchor|NAS}} | 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. (See also AN- and MS-.) |
| {{Visible anchor|NC}} | National Coarse; numerical control | The [U.S.] National Coarse series of pre-1949 corresponds today to the Unified National Coarse (UNC) of the Unified Thread Standard. |
| {{Visible anchor|NCM}} | nonconforming material(s) | This abbreviation is used in a machine shop when recording nonconformances (out of tolerance, etc.). For example, "An NCM tag was tied to the scrap part." |
| {{Visible anchor|NCR}} | nonconformance report | A report listing nonconformances (out of tolerance, etc.). Helps to analyze system weaknesses (such as worn-out equipment, operators in need of more training, or risky practices). |
| {{Visible anchor|NEC}} | 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. |
| {{Visible anchor|NEF}} | National Extra Fine | The [U.S.] National Extra Fine series of pre-1949 corresponds today to the Unified National Extra Fine (UNEF) of the Unified Thread Standard. |
| {{Visible anchor|NF}} | National Fine | The [U.S.] National Fine series of pre-1949 corresponds today to the Unified National Fine (UNF) of the Unified Thread Standard. |
| {{Visible anchor|NL or N/L}} | notes list | A list of notes that appears somewhere on the drawing, often in the upper left corner. |
| {{Visible anchor|NOM}}[2] | nominal |
| {{Visible anchor|NORM}} or NORMD | normalized | referring to normalization, a stress-relieving heat treatment. See also HT TR. |
| {{Visible anchor|NPS}} | Naval Primary Standard[3] | (Not to be confused with annotating strait pipe as "NPS", which should instead be annotated NPSM, NPSL, or NPSH[4]) |
| {{Visible anchor|NPT}} | National Pipe Taper | A subset series of the Unified Thread Standard. |
| {{Visible anchor|NS}} | 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. |
| {{Visible anchor|NSCM}} | National Stock/Supply Code for Manufacturers | An older name for "CAGE code". Also FSCM (Federal Stock/Supply Code for Manufacturers). |
| {{Visible anchor|N&T}} or N/T or NT | normalized and tempered | A form of heat treatment in which the metal is first normalized (stress-relieved) and then tempered. Compare H&T. |
| {{Visible anchor|NTS}} | not to scale | See also Engineering drawing > Scale. |
| {{Visible anchor>O}} | | |
| {{Visible anchor|OAL}} | overall length |
| {{Visible anchor|OC}} | on center(s) | That is, centre-to-centre; defines centre-to-centre distance of two features, such as two holes. |
| {{Visible anchor|OD}} | outer diameter |
| {{Visible anchor|ODA}} | original design activity | The entity that originally designed a part. Compare to CDA, the entity that currently has design authority over the part design (definition). |
| {{Visible anchor|OHL}} | 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. |
| {{Visible anchor|OPP}} | opposite | See Part number > Symmetrical parts for explanation. |
| ORIG | original |
| {{Visible anchor>P}} | | |
| {{Visible anchor|pc, pcs}} | piece, pieces | |
| {{Visible anchor|PD}} | pitch diameter | |
| {{Visible anchor|PDM}}, PDMS | product data management, product data manager [app], product data management system [app] | A database(s) and related application(s) 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. |
| {{Visible anchor|PH}} or P/H | precipitation hardening, precipitation-hardened; pilot hole | |
| {{Visible anchor|PHR BRZ}} | phosphor bronze | |
| {{Visible anchor|PL}} or P/L | parts list | A list, usually tabular and often on the drawing (if not accompanying the drawing on a separate sheet), 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. |
| {{Visible anchor|PLM}} | product lifecycle management; plant lifecycle management | See also PDM. |
| {{Visible anchor|PN}} or P/N | part number | |
| {{Visible anchor|POI}} | 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 (TSC) 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. |
| {{Visible anchor|PSI}} | pounds per square inch | A unit of measurement for pressure. See also KSI. |
| {{Visible anchor|PTFE}} | polytetrafluoroethylene | Also well known by the brand name Teflon. |
| {{Visible anchor|PVC}} | polyvinyl chloride |
| {{Visible anchor>Q}} | | |
| {{Visible anchor|QMS}} | 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. |
| {{Visible anchor|QTY}} or qty | quantity | |
| {{Visible anchor>R}} | | |
| {{Visible anchor|R}} | radius | Radius of an arc or circle. Flats and reversals (falling within the dimensional tolerance zone) are tolerated unless "CR" (controlled radius) is explicitly specified. |
| {{Visible anchor|RA}}, Ra | roughness, average; Rockwell A scale | See surface roughness; see Rockwell scale. |
| {{Visible anchor|RB}}, Rb | Rockwell B scale | See Rockwell scale. |
| {{Visible anchor|RC}}, Rc | Rockwell C scale | See Rockwell scale. |
| {{Visible anchor|REF}} or ( )[2] | reference | The dimension or note is given only for reference and thus is not to be used as a part acceptance criterion (although it may be used as an aid to production or inspection). 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" (non-reference) 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. |
| {{Visible anchor|REQD}} or REQ'D | required | For example, "4 REQD" written next to a fastener means that four of those fasteners are required for the assembly. |
| {{Visible anchor|REV}} | 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 (rev block) is a tabular area on the drawing (typically in the upper right corner) 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 (EOs, ECOs, DCNs, ECNs) 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 (CAD, CAM, PDMSs), 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.[5] |
| {{Visible anchor|RFS}} | regardless of feature size | A material condition (or more precisely, freedom from such) in GD&T. Means that a given geometric tolerance is true in relation to a certain datum regardless of its actual size (LMC ≤ actual size ≤ MMC). |
| {{Visible anchor|RH}} | right-hand | Referring to handedness, such as the helix handedness of screw threads or the mirror-image handedness of a symmetrical pair of parts. |
| {{Visible anchor|RHR}} | roughness height reading | See surface roughness. |
| RL | Reduced Level or Relative Leve | Surface Level |
| {{Visible anchor|RMA}} | return material authorization | See also RTV. |
| {{Visible anchor|RMS}} | 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. |
| {{Visible anchor|RT}} 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 (plating, painting, etc.). |
| {{Visible anchor|RTP}} | 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. |
| {{Visible anchor|RTV}} | 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. |
| {{Visible anchor|RZ}}, Rz | roughness, mean depth | See surface roughness. |
| {{Visible anchor>S}} | | |
| {{Visible anchor|SAE}} | 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. |
| {{Visible anchor|SC}} 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. |
| {{Visible anchor|SF}} or S/F | spotface slip fit | |
| {{Visible anchor|SFACE}} or S/FACE | spotface | |
| {{Visible anchor|SHCS}} | socket head cap screw | A cap screw with a socket head (usually implying a hex socket, driven with a hex key. |
| {{Visible anchor|SHN}} | shown | See Part number > Symmetrical parts for explanation. |
| {{Visible anchor|SHSS}} | socket head set screw | A set screw with a socket head (usually implying a hex socket, driven with a hex key. |
| {{Visible anchor|SI}} | Système international [d'unités] [International System of Units] | The metric system in its current form (latest standards). |
| {{Visible anchor|SN}} or S/N | serial number |
| {{Visible anchor|SOL ANN}} | solution anneal, solution annealed |
| {{Visible anchor|SPEC or spec}} | specification |
| {{Visible anchor|SPHER ANN}} | spheroidize anneal |
| {{Visible anchor|SPOTFACE}} | Spot facing |
| {{Visible anchor|SR}} | spherical radius | Radius of a sphere or spherical segment. |
| {{Visible anchor|SS}} or S/S | stainless steel; supersede | 1. Stainless steel, see also CRES. 2. Supersede/supersedes/superseded, refers to when one document (specification, standard, drawing, etc.) replaces (supersedes) another (see also revision control). |
| {{Visible anchor|SST}} | stainless steel | A somewhat unusual abbreviation; spell out for clarity. "SS" or "CRES" are more likely to be recognized with certainty. |
| {{Visible anchor|STD}} | Standard |
| {{Visible anchor|STEP}} | Standard for the Exchange of Product Model Data | A standard format defined by ISO 10303 for MBD data generation, storage, and exchange. |
| {{Visible anchor|STA}} | solution treated and aged |
| {{Visible anchor|STI}} | screw thread insert | |
| {{Visible anchor|STL}} | steel |
| {{Visible anchor|STK}} | stock | A nominal dimension for the stock material, such as bar stock |
| {{Visible anchor|SW}} | Schlüsselweite | Translates as Key or Wrench Width. Width across flats, often found on drawings of german origin. |
| {{Visible anchor>T}} | | |
| {{Visible anchor|TAP}} | tapped hole | Usually implies drilling a hole if the hole does not already exist. |
| {{Visible anchor|TB or T/B}} | 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 (usually the part name); drawing number (usually the part number); names and/or ID numbers relating to who designed and/or manufactures the part (which involves some complication because design and manufacturing entities for a given part number often change over the years due to mergers and acquisitions, contract letting, privatization, and the buying and selling of intellectual property—see CDA and ODA); company name (see previous comment); initials/signatures of the original draftsman (as wells as the original checker and tracer in the days of manual drafting); initials/signatures of approving managers (issuance/release-to-production information); cross-references to other documents; default tolerancing values for dimensions, geometry, and surface roughness; raw-material info (if not given in a separate list/bill of materials); and access control information (information about who is authorized to possess, view, or share copies of the information encoded by the drawing, e.g., classification notices, copyright notices, patent numbers). Drawing revision (versioning) information is not always included in the title block because it often appears in a separate revisions block. |
| {{Visible anchor|TDP}} | 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 (drawing change notices), 3D model datasets, data tables, memoranda, and any special conditions called out by the purchase order or the companies' terms-and-conditions documents. |
| {{Visible anchor|THD}} or thd | thread |
| {{Visible anchor|THK}} or thk | thickness |
| {{Visible anchor|THRU}} | 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.[6] |
| {{Visible anchor|THRU ALL}} | 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.[7] |
| {{Visible anchor|TIR}} | total indicator reading; total indicated run-out | For measurements of eccentricity and other deviations from nominal geometry |
| {{Visible anchor|TOL}} | tolerance, tolerancing |
| {{Visible anchor|TSC}} | theoretical sharp corner(s) | See discussion at SC and POI. |
| {{Visible anchor|TY}} | type | For an explanation of "type" abbreviated as "TY", see the example given at "CL" meaning "class". |
| {{Visible anchor|TYP}}[2] | 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 "(TYP)" 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 describe 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. |
| {{Visible anchor>U}} | | |
| {{Visible anchor|UAI}} | use as-is | One of the possible MRB dispositions. Others include scrap and rework. |
| {{Visible anchor|ULL}} | 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. |
| {{Visible anchor|UNC}} | Unified National Coarse | A subset series of the Unified Thread Standard. |
| {{Visible anchor|UNEF}} | Unified National Extra Fine | A subset series of the Unified Thread Standard. |
| {{Visible anchor|UNF}} | Unified National Fine | A subset series of the Unified Thread Standard. |
| {{Visible anchor|UNJC}} | 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 (such as in aircraft). |
| {{Visible anchor|UNJF}} | 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 (such as in aircraft). |
| {{Visible anchor|UNO}} | unless noted otherwise | A fairly well-known abbreviation, but to avoid confusion, spell out. |
| {{Visible anchor|UNS}} | 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. |
| {{Visible anchor|UON}} | unless otherwise noted | A little-used (thus not well recognized) abbreviation. To avoid confusion, spell out. |
| {{Visible anchor|UOS}} | unless otherwise specified | A fairly well-known abbreviation, but to avoid confusion, spell out. |
| {{Visible anchor|USASI}} | United States of America Standards Institute | Former name for ANSI (1966–1969). |
| {{Visible anchor|USS}} | United States Standard; United States Steel | U.S. Standard threads became the National series (e.g., NC, NF, NEF), which became the Unified National series (e.g., UNC, UNF, UNEF); 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. |
| {{Visible anchor|UTS}} | ultimate tensile strength; Unified Thread Standard |
| {{Visible anchor>V}} | | |
| {{Anchor|v_meaning_finish}} v | finish | A letter v (Latin small 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 (italic) f (see herein f). Later the ASA convened upon a letter V (specifically a sans-serif V) touching the surface. Soon this evolved into the "check mark" sign with accompanying number that tells the reader a max roughness value (RMS, microinches or micrometres) for the machined finish, to be measured with a profilometer. |
| {{Visible anchor>W}} | | |
| {{Visible anchor|WC}} | tungsten carbide | The "W" comes from the element symbol for tungsten, W, which comes from the German Wolfram. |
| {{Anchor|WI_wrought_iron}} 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. |
| {{Anchor|WI_within}} W/I, w/i | within | A little-used abbreviation. Better to spell out for clarity. |
| {{Anchor|WO_without}} W/O, w/o | without | Better to spell out for clarity. |
| {{Visible anchor>X}} | | |
| {{Visible anchor|_X_}} | 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° |
| {{Visible anchor|X}}[2] or ( ) | number of places—for example, 8X or (8) | 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. (Note on character encoding: Although in typography (including Unicode) the letter X and the multiplication sign (×) are distinct characters with differing glyphs, it is a longstanding tradition in engineering drawing that the letter X is interchangeable with the multi sign, unless otherwise specified by the CAx systems used.) |
| {{Visible anchor>Y}} | | |
| {{Visible anchor|Y14.X}} | — | 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. |
| {{Visible anchor|YS}} | yield strength |
| {{Visible anchor>Z}} | | |
|
1. ^{{Harvnb|ASME|2007}}.
2. ^1 2 3 4 5 6 7 8 {{Citation | last = Sheaffer | first = M. K. | last2 = Thomas | first2 = G. R. | last3 = Dann | first3 = R. K. | last4 = Russell | first4 = E. W. | title = Engineering Drawings for 10 CFR Part 71 Package Approvals | date = May 1998 | pages = 11–12 | url = http://www.orau.org/documents/ivhp/health-physics/5502.pdf | accessdate = 2011-06-25}}.
3. ^ASME Y1438-2007 page 102
4. ^ANSI/ASME B1.20.1-1983 Section 6.1
5. ^{{Harvnb|ASME|1997}}.
6. ^{{cite book|title=Dimensioning and Tolerancing, ASME Y14.5-2009|year=2009|publisher=American Society of Mechanical Engineers|at=pp. 16, 17; paragraph 1.8.10|location=NY|isbn=0-7918-3192-2|authorlink=ASME}}
7. ^{{cite book|title=Dimensioning and Tolerancing, ASME Y14.5-2009|year=2009|publisher=American Society of Mechanical Engineers|at=p.16; paragraph 1.8.10|location=NY|isbn=0-7918-3192-2|authorlink=ASME}}