Designed to fill a single A4 sheet. The legality badges are the useful bit. Free to print, copy and hand out — no permission needed.

Dalloway Precision Reference chart · ASME Y14.5 / ISO 1101

GD&T symbols chart

All fourteen geometric characteristics, with the two facts most published charts leave out: which controls may take a datum, and which may take a material condition modifier.

Per ASME Y14.5. *MMC/LMC is permitted only in specific cases — see the rules below. Badges: FormOrientationLocationProfileRunout. Edition note: ASME Y14.5-2018 withdrew concentricity and symmetry, taking the official count from 14 to 12. Both remain in Y14.5-2009 and ISO 1101 and still appear on drawings, so they are listed here — but new designs should use position or runout instead.

⏤

StraightnessFormno datumMMC*

How much a line element or an axis may bow away from perfectly straight.

⏥

FlatnessFormno datumMMC*

All points of a surface must lie between two parallel planes the tolerance apart. No datum — the surface is judged against itself.

○

CircularityFormno datumno MMC

Each individual cross-section must lie between two concentric circles the tolerance apart. A slice-by-slice control, not a whole-feature one.

⌭

CylindricityFormno datumno MMC

The whole surface must lie between two coaxial cylinders the tolerance apart. Controls roundness, straightness and taper simultaneously.

∠

AngularityOrientationdatum reqMMC*

The feature must lie within a zone at the specified basic angle to the datum. Controls orientation only, not location.

⊥

PerpendicularityOrientationdatum reqMMC*

The feature must sit within a zone exactly 90° to the datum. It says nothing about where the feature is, only how it is oriented.

∥

ParallelismOrientationdatum reqMMC*

The feature must lie within a zone parallel to the datum. Again orientation only — it does not fix the distance.

⌖

PositionLocationdatum reqMMC*

The feature axis or centre plane must lie within a zone centred on the theoretically exact (basic) location. The workhorse of GD&T.

◎

ConcentricityLocationdatum reqno MMC

The derived median points of the feature must lie within a cylindrical zone about the datum axis. Note this is about median POINTS, not the surface.

⌯

SymmetryLocationdatum reqno MMC

The derived median points of a feature must lie within a zone about the datum centre plane. The planar analogue of concentricity.

⌒

Profile of a LineProfiledatum optno MMC

Each 2D cross-section of the outline must lie in a zone about the true profile. Without datums it controls form only; with them, also orientation and location.

⌓

Profile of a SurfaceProfiledatum optno MMC

The whole surface must lie in a 3D zone about the true profile. With datums it controls form, orientation and location at once, which is why it can replace several other callouts.

↗

Circular RunoutRunoutdatum reqno MMC

Full indicator movement at a single cross-section as the part is rotated about the datum axis. Combines circularity and coaxiality in one reading.

⌰

Total RunoutRunoutdatum reqno MMC

Indicator movement across the entire surface while rotating about the datum axis. Adds cylindricity and taper control to circular runout.

The material condition rules, precisely

Position takes MMC or LMC freely. Straightness only on a derived median line and flatness only on a derived median plane — both features-of-size cases. Perpendicularity, angularity and parallelism only when the toleranced feature is a feature of size, never a plain surface. Where MMC applies, departure from MMC earns bonus tolerance — always worth checking before scrapping a part that failed on paper.

Runout never takes a modifier

Uniquely, runout takes MMC/LMC nowhere — not even on the datum reference. Profile never takes it on the tolerance value either, though a datum letter in the same frame still can. That is datum shift, not bonus tolerance.

The four form controls never take a datum

Straightness, flatness, circularity and cylindricity all judge a feature against itself. If you see a datum in a form control frame, the drawing is wrong.

ASME vs ISO — the difference that bites

ASME Y14.5 applies Rule #1 silently: perfect form at MMC on every feature of size unless you say otherwise (circled I switches it off). ISO 8015 defaults to the opposite — independency — and you must add circled E to require the envelope. The same drawing means different things under each.

Dalloway Precision Engineering Ltd — GD&T symbols chart. UK subcontract CNC machining, Lye, West Midlands.
Typical reference values: the governing standard or your material certificate takes precedence.

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