What is a reference dimension in GD?

A Reference Dimension is a dimension given to any features that are just for reference – or visualization purposes. These are called out on a drawing using parenthesis (i.e., 5.125). It also could be a dimension that is described on another drawing or elsewhere. Either way, the dimension does not get inspected.

How the reference dimensions are mentioned?

Reference dimensions are shown on a drawing as a value enclosed in parentheses. An alternate method is to follow the dimension with “Reference” or “Ref”. The use of “Ref” or enclosing the dimension inside parentheses are by far the most common notations used. These notations are specified in ASME Y14.

Can a basic dimension be a reference?

A basic dimension is a dimension of where a feature is theoretically located (or where it is intended to be located). It must have some other tolerance to it from GD. A reference dimension is just there to reference, but can be completely taken off the drawing to make sense.

What does REF mean on drawing?

REFERENCE
REF on drawings is generally defined as REFERENCE. These dimensions are to be used as reference only.

What is the MMC virtual condition size of one of the holes?

1, the diameter of the virtual condition is the diameter of the MMC shaft plus the diameter of the position tolerance zone. For an internal feature of size, such as a hole, the virtual condition is equal to the size at MMC minus the size of the tolerance zone.

What does 2x mean on a drawing?

Typical on an engineering drawing identifies a repeated feature. This is identical to a feature which is identified as 2x or 5x. A typical dimension callout will occasionally be followed by a 2x, 5x or similar, to specify the quantity of features which are tolerance the same.

Can you tolerance a reference dimension?

A (ref) dimension has no tolerance, so it would be impossible for it to be non-conforming.

What does REF mean on blueprint?

What is a boxed dimension in GD?

Because basic dimensions are theoretically perfect dimensions, there are no tolerances associated with them. A basic dimension is noted as a dimension with a box around it and must mathematically relate back to the Datum Features. In ISO standards, basic dimensions are called TEDs – Theoretically Exact Dimensions.

GD Training Definitions Reference Dimension- A dimension, usually without tolerance that is used for information purposes only. It does not govern production or inspection operations. A reference dimension is a repeat of a dimension or is derived from other values on the drawing or related drawings.

What is a reference dimension?

Reference dimensions are simply placed on a drawing or blueprint for reference. They have no tolerance associated with them. No matter how far off the given value a reference dimension is, it would never be cause for rejection.

Why do we need GD symbols for dimensions?

These dimensions are placed in boxes and never have a tolerance following them. As you could guess, though, making something hit an exact location or dimension would be impossible for anything that we make. A basic dimension of .375: This is why we need something else to give the dimension a tolerance – and this is where our GD symbols come in.

What is the ASME standard for GD?

The current standard for GD is ASME Y14.52009, from the American Society of Mechanical Engineers. It replaces the 1994 version. The rectangular box that contains a GD callout is known as the “feature control frame.”.