What is Geometric Dimension and tolerancing?

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GD and T

The use of dimensional and geometrical tolerance in combination is known as Geometric Dimension and tolerancing.

In the above image; Let consider the example of Inspection of a circle having a diameter of 27.5 mm with tolerance 0.5 mm(the acceptable range is 27 mm to 28 mm). Product A is within the tolerance limit and the same geometry. On the other side Product B also within tolerance limit but not in our required geometry.

There are many standards of Geometric Dimension and tolerancing like National, International as follow(the most common is ISO)

International Standard

ISO 1101:2017 (Geometrical product specifications (GPS) — Geometrical tolerancing — Tolerances of form, orientation, location, and run-out)

Read more aboutISO

National Standards

-United States

ASME Y 14.5:2009

-United Kindom

BS 8888:2013


DIN Standards

The first thing is to know which standard your industry using, Most common is ISO standard due to its global reach.

The reason behind the development of this standard is to build a common understanding between Designer, Manufacturer, and inspector.

I.e. Common language of AutoCAD Designer, Production engineer, and quality engineer.

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