GD&T

What is the feature control frame symbol for least material condition?

An "L" inside of a circle.

What is the feature control frame symbol for maximum material condition?

An "M" inside of a circle.

What is an Inclined Datum Feature?

An Inclined Datum Feature is a datum feature that is at an angle other than 90° relative to the other defined datums.

What are the 5 categories of GD&T characteristics?

Form, Profile, Orientation, Location, or Runout.

Datums imitate...

...the final function of the part.

Datums define the sequence in which the ______________come in contact with the __________________.

...the part surfaces come in contact with the inspection equipment.

If no symbol is shown in the feature control frame, then...

...the zone will be two parallel straight lines, two parallel planes, or uniform boundaries

What is a Basic Dimension?

A Basic Dimension (or Basic) is a theoretically exact number, inside a box, that defines the exact size, location, or orientation of a part feature.

Define "datum feature."

A Datum Feature is a part feature that is identified on the print by a datum identification symbol.

What is a Datum Identification Symbol?

A Datum Identification Symbol is a symbol that visually defines the datum plane, axis, or centerplane of a feature.

Define "datum."

A Datum is a theoretically exact plane, point, or axis derived from the Datum Feature Simulator.

What is a Datum?

A Datum is a theoretically exact plane, point, or axis from which a dimensional measurement is made. It is identified on an engineering drawing with a "datum identification symbol."

What is a Geometric Characteristic?

A Geometric Characteristic is one of 14 symbols in the geometric tolerancing system that is used to control the size, location, orientation, and form of part features.

What is Coordinate Tolerancing?

A dimensioning system that uses limit or plus-minus tolerancing for certain dimensions.

Define a "feature."

A feature is a physical portion of a part, such as a surface, edge, hole, or slot.

Define a "feature of size."

A feature of size (FOS) is a cylindrical or spherical surface, drilled hole, or set of two opposed elements or parallel surfaces associated with a size dimension.

Define Geometric Tolerance.

A general term used in the geometric tolerancing system. It applies to tolerances used to control size, location, orientation, and form.

What are some examples of a feature?

An edge of a hole, a hole or boss, an angled surface, or a chamfered surface.

What are Coplanar Datum Features?

Coplanar Datum Features are where two or more datum features on the same plane are defined as a datum.

A surface on the part from which a measurement is made is called a:

Datum Feature.

Which geometric characteristics never use datums?

Flatness, Straightness, Circularity, and Cylindricity.

What is the term for a very precise, symbol-driven, engineering language consisting of precise definitions and symbols that helps to assure form, fit, and function of individual part features and relationships?

GD&T.

What are some examples of feature of size?

Holes, slots, thickness of material, or any other part feature that has a size dimension associated with it (TIP: if you can drive a centerline or a center plane from the feature, it is a feature of size).

Define maximum material condition (MMC).

Maximum Material Condition (MMC) is the condition where a feature of size contains the maximum amount of material within its stated limits of size.

What are modifiers?

Modifiers are symbols within the feature control frame that can increase the amount of the stated geometric tolerance or extend the length of the tolerance zone. They are contained in the tolerance or datum compartments (2nd or 3rd frame).

Rule #1 states that:

Perfect form at MMC is required.

Which geometric characteristics always use datums?

Perpendicularity, Angularity, Parallelism, Position, Concentricity, Symmetry, Circular Runout, and Total Runout

What are the three different types of datums that can be selected?

Planar Datums, Centerline (axis) Datums, and Centerplane Datums.

What are the three datum reference frames?

Primary datums, secondary datums, and tertiary datums.

Which geometric characteristics sometimes use datums?

Profile of a Line and Profile of a Surface.

Rule #2 states that:

RFS is the default for all geometric controls.

What are the six degrees of freedom?

Rotation around the x, y, and z axes, and translation around the x, y, and z axes.

Do basic dimensions have tolerances?

Since they are theoretically exact, they do not have tolerances associated with them.

What is the "3-2-1" rule?

The "3-2-1" rule defines the minimum number of points of contact required for a part with its primary, secondary, and tertiary datum planes.

What is the Datum System?

The Datum System is a set of Y14.5-defined rules and symbols that aid in communicating to the inspector how the dimension is to be located for inspection.

What is a Feature Control Frame?

The Feature Control Frame is a rectangle that contains information detailing the geometric characteristic, the tolerance zone shape, the geometric tolerance, modifiers, and the datum references.

For purposes of measurement, a datum is established by:

The axis or plane established by the inspection equipment.

Define least material condition (LMC).

The condition where a feature of size contains the least amount of material within its stated limits of size.

Describe a Datum Identification Symbol.

The datum letter is contained inside of a rectangular box. A stem attaches to a triangle that is either filled or unfilled.

In which compartment of the Feature Control Frame is the Geometric Characteristic located?

The geometric characteristic is located in the first compartment of the feature control frame.

A datum feature simulator is:

The inspection equipment (such as a surface plate) used to establish a datum.

In a planar datum application, which datum plane must be contacted by three points?

The primary.

Define the phrase "degrees of freedom."

The rotation and movement (translation) of a part in space.

In what compartment of the Feature Control Frame is the geometric tolerance contained?

The second compartment.

In what compartment of the feature control frame is the datum located?

The third compartment.

On a part with planar datums, how many datums need to be referenced in the feature control frame if the part is to be fully constrained?

Three.

True or False: Datums assure repeatability for location of the part for inspection.

True.

True or False: Datums specify which surfaces on the part are to be used for inspection purposes.

True.

What is the minimum number of contact points for a secondary datum?

Two.

What are two questions that highlight the shortcomings of implied datums?

Which surface should contact the inspection equipment? ...and... In what sequence should the part be brought into contact with the inspection surface?

Unless otherwise specified, all geometric tolerances apply to the full depth, length, and width of the feature. a) True b) False

a) True

Dimensions shall be selected and arranged to suit the manufacturability and inspectability of a part. a) True b) False

b) False Dimensions shall be selected and arranged to suit the function and mating relationship of a part and shall not be subject to more than one interpretation.

Which of the following is not a problem with coordinate tolerancing? a) Undefined reference surface b) Undefined reference surface precedence c) Inflexible tolerance zones d) Square or rectangular shaped tolerance zones e) Lack of communication of function of part f) Dimensioning a diameter, radius, or counterbore depth

f) Dimensioning a radius or counterbore depth.

In order for a tolerance zone shape to be cylindrical, what symbol must be present in the second compartment of the Feature Control Frame?

Ø (Diameter)