Basic tutorial in Geometric Tolerancing GDT
To provide basic skills to specify or interpret geometric tolerances. gdt training

Understanding the international engineering language of Geometric Dimensioning & Tolerancing (GDT), gd t symbols is essential for communicating in today's highly competitive global marketplace. This tutorial builds the ability to read and interpret GDT symbols, which provide detail information about the function and relationship of part features such as, dimensioning, tolerance, runout, datum, profile etc.

Part I : Introduction to
Dimensioning and tolerancing GDT

Dimension

A dimension is a numerical value expressed in an appropriate unit of measure. It is indicated on a drawing along with line, arrow, symbols and notes to define the size and specification of an object.

(Fig. 1 )

Reference dimension

Reference dimension is used only for information purposes. The definition REF shall be indicated immediately under or beside the dimension.
Normally it is either a duplication of a dimension or it is the accumulated value of other dimensions.

Tolerance

GDT Tolerance is the allowable variation of a dimension. It is the difference between the maximum and minimum limits. All dimensions except basic, reference, nominal, maximum or minimum shall have a tolerance.
See Fig. 1.

Next >> Part II . Maximum & Minimum metal condition