⌖ 0 Zero geometric tolerance in MMC

Controls the real location of a feature of size (hole, shaft, slot, median plane) relative to a datum system, comparing its real position with its exact theoretical position (basic dimension). The tolerance zone is normally a cylinder (with ⌀, for holes or shafts) or two parallel planes (for slots or median planes) centered exactly on the basic position. It advantageously replaces the classic ± coordinate tolerancing: it defines a real (circular) acceptance zone, not a square, giving more usable area for the same functional control.

Controls that a feature (face, axis or median plane) forms 90° to the reference datum. It's an orientation tolerance: it says nothing about the form of the feature itself (a face can be perfectly perpendicular on average and still not be flat, which is why it's wise to also state flatness if applicable). With ⌀ before the value, the tolerance zone is cylindrical around the theoretically perpendicular axis; without it, it's two parallel planes oriented at 90° to the datum.

Controls that a feature (face, axis or median plane) stays parallel to the datum, with no theoretical angle other than 0°. The tolerance zone is two planes (or a cylinder, if it carries ⌀) parallel to the datum, separated by the stated value. As with perpendicularity, it doesn't control the feature's own form: a face can be parallel on average to its datum and still not be flat.

Limits the variation of a real surface between two theoretical parallel planes separated by the tolerance value: the whole surface must fit between both planes, regardless of its orientation to other faces of the part (that's why it carries no datum). Passing flatness doesn't guarantee the face is square or parallel to another — perpendicularity and parallelism control that separately.

Combines in a single requirement the roundness of all cross-sections, the straightness of the generatrices (longitudinal lines) and the taper along the whole cylindrical surface. The tolerance zone is two coaxial cylinders radially separated by the stated value, within which the entire real surface must stay. Requiring no datum, it's the most complete cylindrical form tolerance and also the most expensive to achieve and inspect.

Limits the radial variation of a circular cross-section from a perfect circle, evaluated in a plane perpendicular to the axis at a specific point — not along the whole part (that's what cylindricity is for). The tolerance zone is two concentric circles radially separated by the stated value; the real section must stay between them. It needs no datum: it's roundness of that section relative to itself, not to an external reference axis.

Limits the deviation of a real line (a generatrix, an edge or the axis of a cylinder) from a theoretically perfect straight line. The tolerance zone is the space between two parallel straight lines separated by the stated value, evaluated point by point along that line. It's a pure form tolerance: by default it requires no datum, and it controls only the specific line indicated on the drawing (an edge, a generatrix seen in profile), not necessarily the whole axis of the part — that's what axis straightness is for.

Controls the orientation of a feature relative to a theoretical angle (basic dimension, boxed) other than 0° or 90° to a datum — for those two specific cases parallelism and perpendicularity are used. The tolerance zone is a band oriented exactly at the basic angle: the tolerance value is always expressed in linear units (mm), like all other GD&T tolerances, never in degrees or minutes.

Requires the midpoint of every cross-section of the controlled feature (not the whole surface, but the centers of each cut) to coincide with the datum axis. It's among the most demanding and hardest-to-verify tolerances in the whole GD&T system, because it forces evaluating the center of infinite sections instead of the surface as a block.

Controls the coincidence of the derived axis of a cylindrical feature with the axis of an also-cylindrical datum. Unlike concentricity (which compares centers of individual sections), coaxiality compares the feature's complete axis with the datum axis, treating both as derived straight lines.

Controls that a median feature (slot, tab, median plane) is centered on the datum's median plane. The tolerance zone is two parallel planes, equidistant from the datum's median plane, within which the real median plane of the controlled feature must fall.

Two or more rows within the same geometric tolerance frame, sharing symbol and datums but with different values: the upper row (PLTZF, pattern-locating tolerance zone) controls the location of the complete pattern relative to the datum system; the lower row (FRTZF, feature-relating tolerance zone) controls only the geometric relationship between the pattern's features among themselves, usually with a tighter tolerance. They are not two independent requirements: the lower row's zone must be contained within the upper row's zone at each feature.

Indicates, via the numeric prefix (4×, 6×, etc.) or the "PATTERN" note, that the frame's geometric tolerance applies to the complete set of repeated features as a single pattern, not to each feature in isolation with its own dimensional tolerance. All the pattern's features share the same datum system and the same theoretical tolerance zone.

Controls, in a specific cross-section, the total variation (combining form and position) of a circular feature or a face when rotated 360° about the datum axis. Unlike roundness (which requires no datum), circular runout does depend on the clamping about the reference axis: eccentricity, ovality and misalignment blend into a single reading, without distinguishing which of the three causes the error.

Controls the combined variation of form, orientation and position of an entire surface (not just one section) when rotating about the datum axis, with the indicator sweeping the whole length or face simultaneously while the part turns. It's more demanding than circular runout because it accumulates the error of all sections into a single reading: a part can pass circular runout section by section and still fail total runout if the error pattern changes progressively along the part (for example, a slight taper).

Controls the form of a complete surface (not just one section) against the three-dimensional theoretical model (CAD or basic dimensions), and can replace several form, orientation and position tolerances in a single requirement if the drawing states it explicitly (profile as a composite tolerance). The tolerance zone is an envelope of constant thickness around the whole nominal surface.

Controls the form of a line (the contour seen in a specific cross-section) against the theoretical profile defined by basic dimensions or by the CAD model, without comparing the whole 3D surface (that's what profile of a surface is for). The tolerance zone is a band following the theoretical contour, of width equal to the stated value; it can be distributed symmetrically on both sides of the nominal profile or unequally (unequally disposed, with the ⊕/⊖ modifier) toward one side.

Extends the scope of a profile tolerance (of a line or a surface) so it automatically applies to the WHOLE closed contour shown in that view, without dimensioning each segment separately. It's indicated with a small circle on the corner of the tolerance frame ("all around"). It differs from applying profile only to a segment marked with a thick line: without the circle, the profile only controls the explicitly indicated segment.

Straightness applied to the derived axis (the theoretical center) of a cylindrical feature, not to its surface. With ⌀ before the value, the tolerance zone is an imaginary cylinder of that diameter within which the real axis must stay over its whole length — not a pair of planes as in line straightness. It's the correct way to control the complete axis of a shank or stud; being a feature of size, it's the only straightness that accepts Ⓜ or Ⓛ.

Allows the surface's real form to vary within the tolerance zone (for example, from expected elastic deformation under load or normal manufacturing variation) while staying true to the nominal form of the associated CAD model. Unlike classic profile, which compares against a single fixed nominal surface, dynamic profile lets that reference surface adjust (translate/rotate/scale within limits) when comparing with the real part, without penalizing form variations that the part's own physics produces.

The geometric tolerance applies when the element has the maximum material allowed by the size tolerance (maximum shaft, minimum hole).

The geometric tolerance applies when the element has the minimum allowable material (minimum shaft, maximum hole).

Projects the position tolerance zone up the hole, typically for studs or screws.

Identifies a surface, axis or physical point that serves as the origin for the rest of the geometric tolerances.

3D coordinate system built from the datums in the order A|B|C.

Exact theoretical dimension without own tolerance; the variation is controlled by the associated geometric tolerance.

Rectangle divided into compartments: symbol, tolerance, modifiers and datums in order.

The order in the framework (A first, then B, then C) defines how the reference system is constructed.

Arithmetic mean of the absolute values of the deviations of the profile with respect to the midline, in the evaluated sampling length.

Mean maximum profile heights over a sampling length; more sensitive to spikes than Ra.

Indicates surface finish requirement (Ra, Rz, process, machining direction).

Indicates that the geometric tolerance dimension or zone is cylindrical or circular.

Indicates depth of a hole, slot or cavities.

Stepped hole with cylindrical cup for screw head.

Cone at the hole entry for a countersunk screw.

Linear and angular dimensions without explicit tolerance are covered by a general rule cited on the plan.

A real axis must lie within the perfect cylinder of maximum diameter; a hole inside the cylinder of minimum diameter.

The surface must be machined; The raw state of casting or rolling is not valid.

Cylindrical or spherical element, or two opposite parallel surfaces, with associated size dimension.

In ASME Y14.5-2018, the square on the corner of the tolerance frame ("all over") extends the profile requirement to the COMPLETE surface of the solid on all its faces, not just the contour visible in a specific view (that would be "all around"). It's the broadest-reaching symbol of the whole profile system: any face of the part not explicitly excluded by a note is subject to the same requirement.

Informative dimension in parentheses, without direct compliance requirement.

Allows the datum to shift within a range to accommodate manufacturing variation while maintaining function.

Defines a point, line or area located on an irregular surface as a datum contact (cast or forged parts).

Circular or rectangular area that defines the effective contact area of the datum.

Contact line as datum on surfaces where one point is insufficient.

Localized contact point used as a datum on irregular or large surfaces.

Composite limit of MMC/LMC size plus/minus geometric tolerance; defines the worst case for assembly or gauge.

Treats several surfaces separated on the drawing as a single feature for GD&T.

The part is measured without external clamping forces or gravity that deform the geometry (thin sheet, rubber, plastic).

It breaks the default rule that size and shape are coupled; shape and size are evaluated separately.

The geometric tolerance does not vary with the actual size of the element; there is no tolerance bonus.

The profile or orientation tolerance is not reduced by the element size limit; evaluates only the geometry.

The profile tolerance zone moves only to one side of the theoretical profile (unilateral).

Defines a plane derived from the intersection of two datums where the oriented or profile tolerance is applied.

The orientation or profile tolerance is applied to a tangent plane composed of the highest points of the irregular surface.

The geometric tolerance applies only to an indicated section of the element, not to its total length.

Allows size tolerance compliance to compensate for geometric tolerance in reverse, under specific ISO rules.

Each GD&T frame is evaluated with its own datum reference frame; It does not accumulate with a simultaneous requirement.

Several GD&T frames share the same datum reference frame without accumulating errors due to re-establishing datums.

The geometric requirement is evaluated on the statistical distribution of a lot, not piece by piece.

It allows moving the geometric tolerance zone within defined limits while maintaining the functional requirement.

Multiple elements share the same geometric tolerance zone rather than independent zones.

Angular cut on edge, with depth and angle (usually 45°).

Inclination relationship between two surfaces or draft angle in casting/molding.

Indicates that the cross section is square with the same value on both sides.

Defines a spherical zone around a theoretical point.

Limits a geometric or dimensional requirement to the segment between two indicated elements.

Tolerance with the same positive and negative deviation; most common form in linear dimensions.

Limit level that must not be exceeded in one direction (minimum clearance, maximum height, etc.).

The dimension refers to the distance along the arc, not the chord.

Real length of an unfolded contour (bent sheet metal, developed profile).

Radial dimension of an arc or rounded corner.

The arc must be tangent and its center falls on the bisector of the angle, with a smooth transition.

Radius of a spherical surface.

Indicates conical surface with defined taper relationship with respect to the axis.

Locally machined flat face for a washer or screw seat, without a full counterbore.

Linear or angular dimensional tolerance symmetrical around the nominal value.

Indicates the predominant orientation of the machining marks with respect to the view of the symbol.

Marcas siguiendo trayectoria circular (torneado en cara, fresado orbital).

Cross machining marks in two directions on the surface.

Marks without predominant direction (isotropic surface for lay purposes).

Machining marks predominantly parallel to the line of sight of the symbol.

Marks predominantly perpendicular to the line of sight of the symbol.

Marks in a radial direction with respect to the center of the piece or element.

The surface must not be machined; the original stock must be kept.

Root mean square deviation of the profile; related to Ra but more sensitive to extreme values.

The surface must remain in its raw state; removing material is not allowed.

Groups together several separate elements that must meet a geometric requirement as a functional set.

A combination of size dimension and GD&T framework that govern the same element together.

Set of basic dimensions that define the theoretical geometry without its own linear tolerance.

Indicates that several elements of a circular or linear pattern are distributed at equal angular or linear intervals, without bounding each angle separately.

ASME concept for the composite limit of MMC and geometric tolerance in assembly analysis.

ASME concept for combining LMC with geometric tolerance in worst case clearance calculation.

Indicates how many times an element or dimension appears in the part.

Warns that a specific detail or view does not match the actual proportion of the drawing, usually for clarity or subsequent correction without redrawing.

General note that establishes a default criterion (tolerance, material, finish, radius) valid for the entire piece unless a local dimension explicitly contradicts it.

Indicates that the dimension or detail repeats in equivalent places without dimensioning each one.

The cord must be flat or flush with the base surface.

The cord is slightly recessed (concave) in the center of the fillet.

The cord should protrude convexly from the surface.

Indicates that the weld must penetrate completely with controlled formation on the reverse side.

Indicates use of root support (ceramic, copper, gas) or reinforcement on the opposite side of the joint.

Indicates joint type, size, length and welding process on the manufacturing drawing.

Intermittent weld on both sides of the joint with staggered segments.

Fixation of studs, bolts or pins by arc or resistance on sheet metal or structure.

Joint with edge preparation (V, U, J, etc.) filled with filler material.

Deposit of material on a surface for wear, corrosion or dimensional recovery.

Triangular weld in the union of two pieces, typically 90°.

Welding is carried out in final assembly on site, not in the manufacturing workshop.

Weld in an elongated slot instead of a circular hole.

Weld in alternating segments with defined length and pitch along the joint.

Continuous series of spot welds or a continuous linear seam along a joint.

Union located by resistance or specific process between two sheets.

A weld that fills a hole in an overlying member joining it to the one below.

The weld continues around the entire contour of the joint in the view indicated.