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Mechanical Engineering vocabulary · Tolerances and Measurement

Datum

Meaning in mechanical engineering, with examples

/ˈdeɪtəm/nounCommon term

In mechanical engineering, datum means: A theoretically exact point, line or surface on a part, marked with a letter on the drawing, from which other features are located and measured.

In Turkish: referans, datum, referans yüzeyi

How it is used

Used with GD&T, in drawing checks and on the CMM. Datums are labeled A, B and C, and together they form a datum reference frame. Engineers choose datum features that match how the part is located in the assembly. In engineering the plural is datums, not data.

Example sentences

  1. Datum A is the bottom face that sits on the base plate.

  2. The inspector measured the hole positions from the wrong datum.

Common collocations

  • datum feature
  • datum reference frame
  • primary datum
  • datum surface
  • GD&TShort for geometric dimensioning and tolerancing: a system of drawing symbols that controls the form, orientation, location and runout of features relative to datums.
  • toleranceThe allowed amount of variation in a dimension or property, for example ±0.05 mm. A part is acceptable if its measured value falls inside this range.
  • dimensionA measurement of size or position on a part, such as a length, width, diameter or the distance between two holes, shown as a number on a drawing.
  • technical drawingA precise drawing of a part or assembly that shows its shape, dimensions, tolerances, material and finish, so that it can be made and inspected.
  • inspectionChecking a part, product or machine against a drawing, specification or standard by looking at it, measuring it or testing it.

This word in other fields

The same English word can have a different meaning in another field:

More terms: Tolerances and Measurement

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