Specifying Tolerances and Surface Finish for Sheet Metal and CNC Parts

Last updated: 22 September 2026.

Every standard number and scope statement below is dated and linked to the official or standards-body source in the list at the end of this page. Standards are revised on their own cycles, and the surface-texture standards changed recently — check the current edition before you release a drawing.

1. Two kinds of limit, and why the difference decides everything

A drawing carries two different kinds of limit, and they do different jobs. A general tolerance note applies by default to every dimension you did not tolerance individually. Individual indications apply to the features you did tolerance. ISO 2768-1:1989 is titled precisely for the first job: General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications. Its abstract states that it is intended to simplify drawing indications, that it specifies general tolerances in four tolerance classes, and that it applies to the dimensions of workpieces produced by metal removal or formed from sheet metal. The same scope wording is carried by the second edition now in preparation.

Three consequences follow directly from that scope.

• A general callout is a fallback, not an overview. It governs the dimensions you did not tolerance. It cannot rescue a feature you failed to dimension, and it says nothing about the features you already toleranced.
• It is process-shaped, not product-shaped. One document is meant to serve both a milled part and a formed sheet-metal part — which is why the class you select does more work than the standard number does.
• The edition is part of the specification. ISO 2768-1:1989 is still Published and was last reviewed and confirmed in 2022, but ISO records that it is expected to be replaced by the second edition, ISO 2768, Geometrical product specifications (GPS) — Dimensional tolerancing — Tolerance limits for general specification of linear and angular sizes, which is at stage 60.00, "International Standard under publication". A drawing note that says only "ISO 2768" will mean different documents at different dates.

The question worth more than any chart is whether the note is on the drawing at all. ISO 13920:2023 governs welded constructions rather than machined or formed parts, but the principle it states is the one that protects a buyer everywhere: manufacturing documentation in which dimensions or shape-and-position indications are presented without individually indicated tolerances shall be deemed incomplete if there is no, or inadequate, reference to general tolerances — and, importantly, that exception applies only to temporary dimensions. The same document states that the applicable tolerances are always those which are stated in the drawing. If the drawing does not state them, your inspector has nothing to accept or reject against.

Drawing situation	What should govern it	Why it changes the quotation
Untoleranced linear or angular dimensions on a machined or formed part	A general tolerance note that names the standard, the edition and the class	Every supplier prices the file as written. Without the note, each supplier prices a different assumption
A dimension that carries function — a bore, a mating face, a location	An individual tolerance on that dimension	Individual limits drive process selection, fixturing and inspection effort; they are the real cost drivers
Form, orientation or location that a size tolerance cannot control	A geometric control applied under ASME Y14.5-2018	ASME Y14.5 "establishes symbols, rules, definitions, requirements, defaults, and recommended practices for stating and interpreting" GD&T on drawings, models and related documents
A welded sub-assembly	General tolerances for welded constructions to ISO 13920:2023, with its own four tolerance classes	Weld distortion is a different error budget from machining error, and it needs its own class
A part defined by a 3D model with no dimension or tolerance note	Nothing in the general-tolerance chain has been invoked	The supplier invents the acceptance limits, and so does your inspector — independently

2. General callout or per-feature callout: how to decide

The judgement is not aesthetic. Put an individual tolerance where variation breaks the function. Leave the rest to the general note. Four questions settle most cases.

1. What happens at the limit? Walk the dimension to its extreme and ask what stops working. If the honest answer is "nothing measurable", the property belongs to the general class. If the answer is "the bearing will not seat", it needs its own limit.

2. Does size actually control the thing you care about? Not always. ISO 13920:2023 states that its specifications are based on the independency principle of ISO 8015, according to which the dimensional and geometrical tolerances apply independently of each other. Read that the other way round: a size tolerance does not constrain form, orientation or location. A shaft can sit inside its diameter limits and still be bowed; a plate can be within thickness limits and still be twisted. If the function depends on flatness or parallelism, a general tolerance class built on "customary workshop accuracy" is not the control you are relying on.

3. Can you measure it on arrival? A limit your incoming inspection cannot verify is a limit you have delegated to the supplier's word. Section 6 sets out what is realistic for a normal receiving area, and it is a shorter list than most drawings assume.

4. What is the class actually for? ISO 13920:2023 is explicit that its classes are based on customary workshop accuracy and that the main criterion for selecting one is the functional requirements to be met. That is the honest framing for any general class: it describes what a competent shop normally achieves, not what the process is capable of at its best.

The cost conversation follows from those four questions rather than from a table.

If you...	What you are asking the supplier to do	Where it ends up
Tighten every dimension on the drawing	Hold and verify every dimension, add operations and handling, and manage a wider spread of measurements against a narrower window	You pay for precision on features that do not need it, and you add rejection risk on features that were fine
Leave every dimension to a loose general class	Work to the broadest default the note allows	Parts can conform to the drawing and still fail at assembly — the defect appears downstream, not at goods-in
Tolerance a cosmetic or non-functional face	Nothing the function needs	Cost with no benefit, and an unnecessary argument if the surface is marked
Leave a functional fit to the general note alone	Interpret your intent	A conforming part that does not fit, and a dispute in which the drawing is on the supplier's side

Note the asymmetry. Over-tolerancing converts directly into money and schedule. Under-tolerancing converts into a delayed failure you discover at assembly — usually after the parts have been accepted. The cheapest drawing is the one that tolerances the few features that decide the fit, and leaves the rest alone. Two related decisions sit upstream of this: the material you select sets what the process can hold at all, and the process you select sets the error budget you are working inside.

3. Surface texture: Ra, Rz, and a standard set that just changed

Surface texture is where drawings age fastest, because the standards behind the symbols were replaced recently and most drawings in circulation still cite the old ones.

The parameter set people quote by habit — ISO 4287 for terms and parameters, ISO 1302 for the symbols — is no longer current. ISO 4287:1997 is Withdrawn, and its replacement is ISO 21920-2:2021, which specifies terms, definitions and parameters for the determination of surface texture by profile methods. ISO 1302:2002 is Withdrawn too; its replacement is ISO 21920-1:2021, which specifies the rules for indication of surface texture by profile methods in technical product documentation by means of graphical symbols. ISO 21920-3:2021 completes the set: it specifies the complete specification operator for surface texture by profile methods, and it supersedes the assessment rules of ISO 4288:1996. All three parts are Published, first editions, dated 2021-12.

The transition is not instantaneous. Germany's national metrology institute, PTB, records that profile roughness standards were brought together in the new three-part series of standards ISO 21920, which was published in the course of 2022 and replaces well-known standards such as e.g. ISO 4287, ISO 4288 and ISO 13565-2 and -3, and that a transition phase of several years is assumed for the general implementation of the new standards — so both the withdrawn and the new standards remain in circulation. The practical rule is the one you would apply to any other standard: put the standard number and the year on the drawing, so a supplier reading it knows which set the callout is written in. A drawing that names a roughness parameter without naming the standard it is measured to leaves that open.

The letter in front of the parameter is the profile. ISO 1302:2002 already set the naming key that the current series keeps: parameters relate to the R-profile (roughness), the W-profile (waviness) and the P-profile (structural). So R in Ra and Rz means roughness profile; W means waviness; P means the primary profile. Reading the letter is not a detail — it tells you what was filtered out before the number was measured.

Ra and Rz are different quantities, not two units. This is the single most expensive misunderstanding in surface specification.

Parameter	What it measures, in the terms of the published definitions	Choose it when
Ra	Arithmetic mean surface roughness: the arithmetical mean of the sums of all profile values	You need a general, repeatable shop average. Understand its blind spot: Ra hardly reacts to peaks or valleys, because of the mean-value formation from all profile values, so its significance on its own is rather low
Rz	Maximum height of the roughness profile: the sum of the height of the highest profile peak and the depth of the lowest profile valley within a sampling length lr	As a rule, for most surfaces — it responds to the extremes that Ra averages away
Rz1max	Maximum surface roughness: the largest single value found over the total measured length, rather than an average across it	Individual deviations heavily affect function — sealing faces are the standard example
Rt	Total height of the roughness profile: the sum of the highest peak height and the lowest valley depth within the measured length	You want the worst excursion anywhere along the measured length, not per sampling length
Rmr(c)	Material proportion of the profile: the quotient of the summed material lengths of the profile elements at a specified section height c and the measured length, in per cent	Guide surfaces and sealing surfaces moving against each other — where bearing area, not amplitude, decides the function
RSm	Average groove width: the mean value of the width of the profile elements	Groove spacing matters — print registration, coating keying, appearance on a visible face

Two further points from the same source are worth carrying into a specification.

• Scratches are not roughness. Surface imperfections such as cracks, scratches and dents do not count as roughness and are not measured as roughness; if you need to control them, they have to be toleranced separately as surface imperfections. A drawing that specifies only a roughness parameter has not said anything about that scratch.
• A single reading proves nothing. Roughness readings scatter, and the amplitude parameters — Rt, Rz, Rz1max and Ra — scatter most of all, because a stylus samples one line across a surface that varies everywhere. One measurement therefore cannot show that a limit is observed, and acceptance has to be a rule over several readings rather than a number read off a display. That rule belongs to the standard edition named on the drawing, and it is the thing to quote in the RFQ.

Do not convert between parameters to check a part. Ra and Rz are defined differently on the same filtered profile, so a chart that maps one to the other is a workshop rule of thumb about typical processes, not a metrological equivalence — the ratio depends on the shape of the profile in front of you. Specify the parameter you will measure, and accept against that parameter.

4. Reading the symbol, and notes you can copy

A surface-texture symbol is a small form with defined fields. The field layout below follows the indication rules as published for ISO 1302:2002, which the current indication standard replaces but whose field structure the drawing practice in circulation still uses. In practice: state which standard the symbol set is written to, and use the fields consistently.

Field in the symbol	What it specifies	How to use it in words
Basic symbol	The starting element of every surface-texture indication	Draw the bare symbol, with or without the horizontal bar, and make the standard it is written to explicit in the drawing notes
Position a — single surface finish requirement	The primary parameter and its limit	Name the parameter and the limit value here. The value itself comes from your tolerance analysis, and the assessment rule comes from the standard edition
Position b — further surface requirement	A second parameter, if one surface has to satisfy two requirements	Use it when a sealing or sliding face needs a bearing-area style requirement in addition to an amplitude parameter
Bar across the symbol	Whether material removal by machining is required, or is not permissible	The bar states the process intent: a machined face and an as-formed face carry different requirements even at the same parameter
Position c — machining process	The process or treatment you expect	Name it — turned, ground, or a plating or coating. It tells the supplier which route you expect, and it is where a deviation will show first
Position d — groove direction	The lay of the surface grooves	Parallel, perpendicular, crossed, mixed, concentric, radial or undirected, relative to the view the symbol sits in
Position e — machining allowance	Stock to be left for a later operation	State it where a subsequent machining or finishing step will remove material, so the stock is planned rather than improvised
Upper and lower limit together	A band rather than a ceiling	Where the surface must be neither too rough nor too smooth — a band is a different requirement from an upper limit, and it is harder to hold
Number of single measured lengths	Used when the drawing departs from the default measuring path	State the departure and the reason. It changes the readings, so it belongs on the drawing and on the inspection record
Benchmarking letter	Where there is no room for the full entry	Key a letter to a table elsewhere on the drawing rather than crowding the face
Non-amplitude requirements	Where amplitude is the wrong question	Bearing-area and primary-profile parameters are asked for when the function is contact, sealing or coating adhesion rather than peak height

Two drawing-block notes follow from the above, and both are worth copying rather than paraphrasing:

Unspecified surface texture. A block note in this form: UNSPECIFIED SURFACE TEXTURE: R-profile, Rz, assessed by the multi-reading decision rule of the indication standard named above; the limit value is stated in the drawing schedule. This is the general note, not an individual callout, and it is the one that turns "unspecified" into something a shop can actually work to.

Measuring conditions. A second block note in this form: MEASURING CONDITIONS FOR THE SURFACE TEXTURE CALLOUTS: cut-off wavelength and the number of single measured lengths to be stated on the drawing and on the inspection record. This note exists because the same physical surface yields different readings under different cut-offs, and because a reading is only meaningful together with the conditions it was taken under.

The numbers that go with the conditions are not published here, and deliberately so. The cut-off, the number of single measured lengths and the traversed length are fixed by the standard edition and by the parameter named on the drawing — not by a general rule of thumb. The tables that carry those values sit inside the standards, which are sold rather than published, and the only tables circulating freely are second-hand renderings written against superseded editions. So the page states the parameter and sends you to the edition named on the drawing: your supplier and your drawing must name the same edition, and the inspection record must state the conditions under which the reading was taken. Quoting a value from a copy of an old edition is how two parties end up measuring the same surface and disagreeing.

Two practical consequences are worth carrying into the drawing. If the space on the part surface is too small for the required traversed length, the number of single measured lengths has to be reduced and the reduced number shown on the drawing. If the space is still insufficient, the total height of the primary profile is measured over the available length instead of the roughness profile height. Either way it is a deviation from the default measuring path, and a deviation that is not written down is not a measurement.

Where a drawing element must state something, the division of labour is as follows.

Drawing element	What it must state	Why it cannot be left implicit
Drawing notes block	The general tolerance standard, its edition, and the class you selected	It is the default the whole drawing rests on, and the standard is being replaced — an edition-free note will mean different documents at different dates
Title or revision block	Revision, date, and which document governs if a model is also supplied	Two quotations against two revisions are not comparable
Untoleranced dimensions	Nothing further — they take the general class	Adding limits here is how a drawing gets expensive for no functional reason
Function-critical dimensions	An individual tolerance on the dimension itself	These are the features that fail first, and the general class was never written for them
Form, orientation and location features	A geometric control under the framework your drawing names	Dimensional and geometrical tolerances apply independently, so size control does not cover form
Surface-texture symbols	Parameter, limit, whether it is an upper limit or a band, and where it applies	A parameter with no rule for assessing it is not an acceptance criterion
Drawing notes block, second line	The measuring conditions for the surface callouts, and the standard they are measured to	Readings depend on the conditions, so an unstated condition is an unrepeatable requirement
Separate imperfection note	What counts as an unacceptable scratch, dent or surface defect	A roughness parameter does not express these, so an unspecified defect is not a defect

5. What goes in the RFQ so the quotations compare

A supplier can only quote the file they receive. When two quotations for "the same part" differ, the difference is almost always in the package, not in the price list. Nothing below is a commercial term; it is the technical package.

Item	What to state	Why the quotation moves
Drawing revision and model	Revision letter, date, and whether the 3D model or the drawing governs	Prices quoted against different revisions cannot be compared, and the supplier will build to whichever is cheaper to satisfy
Material and temper	Grade and condition, by the designation your material standard uses	Determines machinability and formability, which sets the achievable limits
General tolerance callout	Standard, edition, and the class	A class is a process instruction. Changing it changes how the shop works the part
Individual tolerances	Named per feature, on the features that carry function	These are the limits that force process choice, fixturing and extra measurement
Geometric controls	Any form, orientation or location control, applied under the drawing's stated framework	Requires datum structure and, usually, CMM time
Surface texture	Parameter (Ra, Rz, Rz1max, Rmr(c), RSm), the limit, whether it is an upper limit or a band, where on the part it applies, and the cut-off	A finish requirement changes tooling, feeds and speeds, and adds finishing operations
Surface imperfections	Anything that a roughness number cannot express — scratches, dents, porosity at the surface	Without it, the defect is not a defect, because nothing was specified
Finish or coating	The treatment specification, and which surfaces are protected	Adds process steps and masking, and can change dimensions after the fact
Critical dimensions list	The short list you will actually measure on arrival	Tells the supplier what they must hold and document, and what they can leave to the general class
Inspection method and acceptance rule	The instrument, the sampling, and the decision rule for parameters measured several times	Assessment rules are not identical, and a rule over several readings is not the same requirement as a single reading
First-article expectation	Whether you want a first-article inspection report, and to what documentation standard	Documentation effort has to be priced in. Where the programme is aerospace, the governing document is one such as SAE AS9102C, which establishes the requirements for performing and documenting first article inspection and states that it is complementary to — not an alternative to — customer and applicable statutory and regulatory requirements
Quantity and repeat demand	Annual volume and how repeatable it is	It decides which process is sensible at all

Two things are worth saying out loud in the RFQ even though they are not line items. First, that the drawing and the callouts are the acceptance criteria — if something is not stated, the supplier is entitled to leave it to the general class. Second, that you will be inspecting to the stated method. A quotation is only comparable between suppliers when the technical package is identical, which is why the quote request should carry the drawing and the callouts rather than a description of the part.

If the finished part also has to clear a market-access regime, ASTM vs CE vs UL sets out which framework applies where. The tolerance and finish callouts fix the geometry; they do not decide the market-entry route.

6. How incoming inspection is actually verified

The verification chain has three links: the instrument, the method, and the record. All three need to be chosen before the parts arrive, because a limit that cannot be measured cannot be enforced.

Instruments. External dimensions are the easy case: calipers, micrometers and height gauges cover most linear work on machined and formed parts, and sheet-metal thickness has its own instrument — a deep-throat sheet metal micrometer is made for measuring the thickness of sheet metal where the throat depth matters. Features that a two-point instrument cannot reach — bores, positions, form, and profile — go to a coordinate measuring machine. Surface texture goes to a stylus instrument.

Instrument verification. For CMMs, the acceptance and reverification basis is the ISO 10360 series, described by ZEISS as an internationally recognised series developed specifically for the acceptance and reverification of coordinate measuring machines, and as defining the requirements and procedures necessary for evaluating their performance. Its parts cover length measurement specifications, machines with a rotary-table fourth axis, scanning mode, single and multiple stylus contacting probing systems, imaging probing systems, and optical distance sensors — so "we checked it on the CMM" is a statement about a specific configuration, not a general one. The same standard covers acceptance tests, reverification tests, calibration documentation and the results of the tests carried out. For stylus surface instruments, calibration and uncertainty are covered in the metrology literature: the UK's National Physical Laboratory publishes a good practice guide on measuring surface texture with a stylus instrument that covers the current international standards, the terminology, how to make and interpret measurements, the calibration of the instruments and how to calculate measurement uncertainties.

Method and decision rule. This is the link most often missing. Multi-point parameters need a decision rule, because a single reading cannot demonstrate compliance. Two families of rule are in general use, and they are not interchangeable:

• The max rule, for parameters carrying the "max" addition: readings are taken at the points where the highest values are expected, and the limit must not be exceeded at any point.
• The 16 % rule, for parameters without the "max" addition: the rule sets out a staged procedure in which further readings are taken and the limit is accepted only if the number of readings found above it stays within what the standard allows.

The arithmetic of both rules, and the number of readings each one requires, are defined in the standard and belong on the drawing or in the referenced document rather than in a summary. What matters commercially is the consequence: whichever rule applies, the number of readings is greater than one. That is the practical cost of a surface callout, and it is why an unqualified roughness callout — a parameter and a limit with no decision rule attached — is a harder requirement than it looks. The supplier has to sample, you have to sample, and the two samplings have to be capable of agreeing. Which brings in the third link.

The record. A first-article inspection report, or a dimensional report with the shipment, is only useful if it states the instrument used, the measuring conditions (cut-off and number of single measured lengths for texture; datum structure and machine configuration for a CMM), and the decision rule applied. Ask for those three things explicitly. Where the programme does require formal documentation, the governing requirements are the documentation standard the customer flows down — SAE AS9102C for first article inspection in aerospace supply chains, revised to emphasise first-article planning, evaluation and re-accomplishment activities, and in current issue since 2023.

Gauge and method capability. Finally, an instrument that reads to a fine resolution is not the same as a measurement system capable of deciding the question. Gauge calibration, measurement systems analysis and gauge repeatability-and-reproducibility are distinct disciplines with their own training and their own subject literature; a receiving area that checks a critical fit should be able to say what its measurement system is capable of, not just what the instrument resolution is. The practical version of this for a buyer is a short conversation: which instrument, which method, which record — and can you show me the method before the order, not after the shipment. That is the same discipline as any other incoming quality plan, and it is easier to agree at the supplier audit stage than to argue about at goods-in.

Feature to verify	Typical method	What the record should show
Overall length, width, height on a machined part	Caliper, micrometer, height gauge	Measured values against the drawing limits, with the instrument identified
Sheet-metal thickness	Deep-throat sheet metal micrometer	Thickness at the stated points, with the instrument identified
Diameter or bore	Micrometer, bore gauge, or CMM	Values against limits; for a CMM, the machine configuration and datum structure
Position, form and profile	CMM under the ISO 10360 verification framework	Datum structure, machine configuration, and values against the stated controls
Surface texture (Ra, Rz, Rz1max, Rmr, RSm)	Stylus instrument	Parameter, readings, the cut-off and number of sampling lengths used, and the decision rule applied
Surface imperfections (scratches, dents)	Visual or optical inspection against a separately stated requirement	The stated acceptance criterion and the method used to judge it

7. When to bring the supplier in, and what to ask

Bring the supplier in when the tolerances are still being chosen, not when the drawing is finished. Four questions do most of the work:

Which edition of the general tolerance standard is your drawing register built on? The general tolerance document is being replaced, and the surface-texture standards were replaced in 2021 and 2022. A supplier who can answer this precisely is a supplier who reads the note rather than the number.

Which parameter, cut-off and number of sampling lengths will you use for the surface callout, and will you put them on the report? The answer tells you whether the finish requirement is being treated as a measurable specification or as a shop impression.

Can you hold these individual tolerances with the process you are quoting — and what changes if one of them tightens? The achievable limits for a given process belong to the supplier's process documentation, not to a web page, and the honest answer includes what the change costs.

How do you control the tolerances that the general class does not cover? Form, orientation and location are the features that fall outside a general callout, and the answer should name the framework your drawing uses.

When the specification is settled, send the drawing, the material, the tolerance callouts and the finish specification rather than a description. A quotation is only comparable between suppliers when the technical package is identical — and the package is what decides whether the part fits when it arrives.

All sources retrieved and HTTP-tested on 2026-09-22. Every standard number, scope statement, quoted definition and numeric value on this page has a row below. Where a value could not be obtained from a citable source, the page states the point qualitatively and directs the reader to the standard itself, or to the supplier's drawing note, rather than supplying a figure.

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Frequently asked questions

Sources

All sources retrieved 22 September 2026. This page is an independent reading of the sources listed; the official pages themselves are the specification.

Fact used on this page	Source
S1 — ISO 2768-1:1989 — General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications. Title verified verbatim. Abstract verbatim: "This part is intended to simplify drawing indications and specifies general tolerances in four tolerance classes. It applies to the dimensions of workpieces that are produced by metal removal or are formed from sheet metal. It contains three tables and an informative annex with regard to concepts behind general tolerancing of dimensions." Page data: Status Published; Edition 1; publication date 1989-11; "This publication was last reviewed and confirmed in 2022. Therefore this version remains current."; "Expected to be replaced by ISO 2768 within the coming months."; 3 pages; ISO/TC 213; ICS 17.040.10; stage 90.92. The page states only that there are "four tolerance classes"; it does not name or letter them	ISO https://www.iso.org/standard/7748.html
S2 — ISO 2768 (Edition 2) — Geometrical product specifications (GPS) — Dimensional tolerancing — Tolerance limits for general specification of linear and angular sizes. Title verified verbatim. Abstract verbatim: "This part is intended to simplify drawing indications and specifies general tolerances in four tolerance classes. It applies to the dimensions of workpieces that are produced by metal removal or are formed from sheet metal. It contains three tables and an informative annex with regard to concepts behind general tolerancing of dimensions." Page data: Status Under development / Under publication; stage 60.00 "Final production steps (up to seven weeks)."; "Will replace ISO 2768-1:1989"; Edition 2; ISO/TC 213; ICS 17.040.40	ISO https://www.iso.org/standard/85741.html
S3 — ISO 21920-1:2021 — Geometrical product specifications (GPS) — Surface texture: Profile — Part 1: Indication of surface texture. Title verbatim. Abstract verbatim: "This document specifies the rules for indication of surface texture by profile methods in technical product documentation by means of graphical symbols. This document does not cover population requirements. NOTE See ISO 18391 for population (batch) specifications." Page data: Published; Edition 1; 2021-12; 49 pages; ICS 17.040.40; life cycle shows it replaces the withdrawn ISO 1302:2002	ISO https://www.iso.org/standard/72196.html
S4 — ISO 21920-2:2021 — Geometrical product specifications (GPS) — Surface texture: Profile — Part 2: Terms, definitions and surface texture parameters. Title verbatim. Abstract verbatim: "This document specifies terms, definitions and parameters for the determination of surface texture by profile methods." Page data: Published; Edition 1; 2021-12; corrected version (en) 2022-06; 78 pages; life cycle lists the withdrawn ISO 4287:1997 (with Amd 1:2009, Cor 1:1998, Cor 2:2005) and ISO 13565-2:1996 and ISO 13565-3:1998 among the documents it supersedes	ISO https://www.iso.org/standard/72226.html
S5 — ISO 21920-3:2021 — Geometrical product specifications (GPS) — Surface texture: Profile — Part 3: Specification operators. Title verbatim. Abstract verbatim: "This document specifies the complete specification operator for surface texture by profile methods." Page data: Published; Edition 1; 2021-12; 29 pages; ICS 17.040.40; life cycle shows it supersedes the withdrawn ISO 4288:1996 (and Cor 1:1998)	ISO https://www.iso.org/standard/72228.html
S6 — ISO 1302:2002 — Geometrical Product Specifications (GPS) — Indication of surface texture in technical product documentation. Title verbatim. Abstract verbatim (excerpt): "This International Standard specifies the rules for the indication of surface texture in technical product documentation (e.g. drawings, specifications, contracts, reports) by means of graphical symbols and textual indications. It is applicable to the indication of requirements for surfaces by means of profile parameters, according to ISO 4287, related to the R-profile (roughness parameters), W-profile (waviness parameters) and P-profile (structural parameters) ... NOTE For the indication of requirements for surface imperfections (pores, scratches etc.), which cannot be specified using surface texture parameters, reference is made to ISO 8785, which covers surface imperfections." Page data: Status Withdrawn; Edition 4; 2002-02; 46 pages; "New version available: ISO 21920-1:2021"	ISO https://www.iso.org/standard/28089.html
S7 — ISO 4287:1997 — Geometrical Product Specifications (GPS) — Surface texture: Profile method — Terms, definitions and surface texture parameters. Title verbatim. Page data: Status Withdrawn; Edition 1; 1997-04; 25 pages; ICS 01.040.17 and 17.040.20; withdrawal of International Standard recorded 2021-12-20; "New version available: ISO 21920-2:2021"	ISO https://www.iso.org/standard/10132.html
S8 — ISO 13920:2023 — Welding — General tolerances for welded constructions — Dimensions for lengths and angles, shape and position. Title verbatim. Abstract verbatim (excerpts): "This document specifies general tolerances for linear and angular dimensions and for shape and position of welded structures in four tolerance classes, based on customary workshop accuracy. The main criterion for selection of a particular tolerance class is based on the functional requirements which are to be met."; "The applicable tolerances are always those which are stated in the drawing. Instead of specifying individual tolerances the tolerance classes according to this document can be used."; "Special provisions can be necessary for complex structures."; "The specifications given in this document are based on the independency principle of ISO 8015, according to which the dimensional and geometrical tolerances apply independently of each other."; "Manufacturing documentation in which linear and angular dimensions or indications for shape and position are presented without individually indicated tolerances shall be deemed incomplete if there is no, or inadequate, reference to general tolerances. This does not apply to temporary dimensions." Page data: Published; Edition 2; 2023-06; stage 60.60; 8 pages; ISO/TC 44/SC 10; ICS 17.040.10 and 25.160.10; replaces ISO 13920:1996	ISO https://www.iso.org/standard/86032.html
S9 — ISO 13920:1996 — Welding — General tolerances for welded constructions — Dimensions for lengths and angles — Shape and position (first edition, now Withdrawn). Abstract verbatim: "Specifies general tolerances for linear and angular dimensions and for shape and position of welded structures in four classes, these being based on customary workshop accuracy. The main criterion for the selection of a particular class should be the functional requirements." Page data: Withdrawn; Edition 1; 1996-08; 5 pages; withdrawal recorded 2023-06-02; superseded by ISO 13920:2023	ISO https://www.iso.org/standard/23313.html
S10 — ASME Y14.5-2018 (R2024) — Dimensioning and Tolerancing. Description verbatim: "The Y14.5 standard is considered the authoritative guideline for the design language of geometric dimensioning and tolerancing (GD&T.) It establishes symbols, rules, definitions, requirements, defaults, and recommended practices for stating and interpreting GD&T and related requirements for use on engineering drawings, models defined in digital data files, and in related documents."; "GD&T is an essential tool for communicating design intent — that parts from technical drawings have the desired form, fit, function and interchangeability." Page data: designation shown as "Y14.5 - 2018 (R2024)"; "This Standard was last reviewed and reaffirmed in 2024. Therefore this version remains in effect."; ASME Y14.5-2018 replaces ASME Y14.5-2009	ASME https://www.asme.org/codes-standards/find-codes-standards/y14-5-dimensioning-tolerancing
S11 — SAE AS9102C — Aerospace Series — First Article Inspection Requirements. Content verbatim: "This standard establishes the requirements for performing and documenting FAI. It is emphasized the requirements specified in this standard are complementary (not alternative) to customer and applicable statutory and regulatory requirements." Rationale verbatim: "This standard was revised to emphasize and enhance the First Article Inspection (FAI) planning, evaluation, and re-accomplishment activities; aligning requirements to the 9100 standard." Page data: shown as "This is a Current Standard"; AS9102C dated 2023-06-27; 22 pages; issuing committee G-14 AAQSC	SAE International https://www.sae.org/standards/as9102c-aerospace-series-first-article-inspection-requirements
S12 — DIN EN ISO 10360 — Standard series for coordinate measuring machines. Verbatim: "The DIN EN ISO 10360 is an internationally recognized series of standards specifically developed for the acceptance and reverification of coordinate measuring machines (CMM). This standard defines the requirements and procedures necessary for evaluating the performance of CMMs." Objectives verbatim: "Establishing standardized procedures for the acceptance and reverification tests of CMMs to ensure consistent quality and performance"; "Creating a unified framework for evaluating the performance of CMMs to promote comparability and interoperability". Main elements verbatim: acceptance tests ("conducted to confirm that a new or modified CMM conforms to the specified requirements"), reverification tests ("regular tests … to ensure the ongoing performance and accuracy of a CMM"), calibration, documentation ("prescribes the necessary documentation for acceptance and reverification tests, including the results and procedures carried out"). Parts listed verbatim: Part 2 CMMs for Length Measurement Specifications; Part 3 CMMs with the Axis of a Rotary Table as the Fourth Axis; Part 4 CMMs in Scanning Mode; Part 5 CMMs Using Single and Multiple Stylus Contacting Probing Systems; Part 7 CMMs Equipped with Imaging Probing Systems; Part 8 CMMs with Optical Distance Sensors	ZEISS (metrology manufacturer documentation) https://www.zeiss.com/metrology/en/explore/topics/din-en-iso-10360.html
S13 — Surface Roughness Measurement — Bulletin No. 1984 (Mitutoyo America), read as a metrology manufacturer's interpretive guide and used on this page for qualitative points only; none of its numeric content is published here. Used for: the R / W / P profile naming and what each profile is filtered to represent; the statement that surface imperfections such as cracks, scratches and dents are not covered by a roughness parameter and have to be toleranced separately; the parameter definitions in qualitative terms (Ra an arithmetic mean of the profile values, Rz a maximum profile height within a sampling length, Rz1max a single worst value over the total measured length rather than an average across it, Rt a total profile height over the measured length, Rmr(c) a material proportion at a stated section height, RSm an average profile-element width); the guidance that a single reading cannot demonstrate compliance and that acceptance therefore has to be a rule over several readings; the observation that Ra reacts weakly to isolated peaks and valleys because it averages all profile values, while Rz and Rz1max respond to the extremes; the preference for a bearing-area style parameter on guide and sealing surfaces moving against each other; and the advice that any reduction in the number of single measured lengths must be shown on the drawing, with the primary-profile total height used instead of the roughness-profile height where space is short	Mitutoyo (metrology manufacturer documentation) https://www.mitutoyo.com/webfoo/wp-content/uploads/Surface_Roughness_Measurement.pdf
S14 — PTB, Working Group 5.14 (Calibration of Roughness Parameters), "Standards in the 2D roughness measuring techniques". Verbatim: "The standards for profile roughness measurement have been revised and brought together in the new three-part series of standards ISO 21920, which was published in the course of 2022 and replaces well-known standards such as e.g. ISO 4287, ISO 4288 and ISO 13565-2 and -3."; "A transition phase of several years is assumed for the general implementation of the new standards. Consequently, both the old and now formally withdrawn standards as well as the new standards and unchanged standards are listed below."; "This list was compiled 2025-12-12." List entries used verbatim: "ISO 4287 [withdrawn, replaced by ISO 21920-2]"; "ISO 4288 [withdrawn, replaced by ISO 21920-3]"; "ISO 21920-1 [NEW, replaces ISO 1302] … Part 1: Indication of surface texture, 2021"; "ISO 21920-2 [NEW, replaces ISO 4287, ISO 13565-2 and -3] … Part 2: Terms, definitions and surface texture parameters, 2022"; "ISO 21920-3 [NEW, replaces ISO 4288] … Part 3: Specification operators, 2021"; also listed: "ISO 12179 … Calibration of contact (stylus) instruments; 2021" and "ISO 8785 … Surface imperfections – Term, definitions and parameters; 1998"	Physikalisch-Technische Bundesanstalt (PTB), Germany's national metrology institute https://www.ptb.de/cms/en/ptb/fachabteilungen/abt5/fb-51/ag-514/ag-514-rauheitskenngroessen/rauheitsmesstechniknormen515.html
S15 — Mitutoyo Training & Education — metrology subject areas and course list. Verbatim subject filter values: "CMM / Calibration / Caliper / Contour / Data Management / Decision Rules / Form / GD&T / Gage Block / Gage R&R / Hardness Tester / Height Gage / Indicator / Measurement Basics / Measurement System Analysis (MSA) / Micrometer / Quality / Repair / Roundness / Surface Roughness / Uncertainty / Vision". Verbatim: "We have product and software training for Mitutoyo measuring equipment, including CMM, vision, and form products. We also offer hands-on skills courses in dimensional measurement, calibration, and repair." Courses cited verbatim include "EDU-205: Introduction to Measurement Systems Analysis (MSA) and Gage R&R (1-day, on-site)", "EDU-450: Geometric Dimensioning & Tolerancing (GD&T) Applied Inspection (2-day, on-site)", "EDU-113: Dimensional Gage Calibration", "EDU-K210: Calibration of Calipers" and "EDU-K220: Calibration of Outside Micrometers, including digital, mechanical, and Vernier models"	Mitutoyo (metrology manufacturer documentation) https://www.mitutoyo.com/training-education/
S16 — NPL Measurement Good Practice Guide No. 37 — The measurement of surface texture using stylus instruments (Leach, R K, 2014; 2nd Edition). Abstract verbatim: "This guide covers the measurement of surface texture using a stylus instrument. It describes the current international standards, introduces the terminology associated with surface texture measurement, and describes how to make measurements and how to interpret the results. The guide also covers the calibration of surface texture measuring instruments and informs the user of such instruments how to calculate measurement uncertainties." Used at abstract level only; the guide's own numeric content was not retrieved	National Physical Laboratory (NPL), UK https://eprintspublications.npl.co.uk/2041/
S17 — Mitutoyo sheet metal micrometer. Verbatim: "Mitutoyo Sheet Metal Micrometers are used to measure the thickness of sheet metal, paper, plastic, and rubber parts where a deep throat micrometer is required."	Mitutoyo (metrology manufacturer documentation) https://mitutoyo.com/educational-resource/sheet-metal-micrometer/
S18 — Engineering judgement, no external source: the cost, schedule and rejection-risk framing in section 2, and the recommendation that a drawing should tolerate only the features that decide function, are craft guidance derived from the scope statements in S1, S8 and S10 and from the qualitative measurement-scatter and decision-rule points described in S13. They are not presented as retrieved findings and contain no numeric claim	— (author's engineering guidance, declared)