Geometric Dimensioning
and
Tolerancing
(GD&T)

What is Geometry?
Geometry is a branch of mathematics that studies the sizes, shapes, positions angles and
dimensions of things.
WHAT IS DIMENSIONS?
Dimension, in common parlance, the measure of the size of an object, such as a box,
usually given as length, width, and height. In mathematics, the notion of dimension is an extension of the idea that a
line is one-dimensional, a plane is two-dimensional, and space is three-dimensional.

TYPES OF Dimension ?
*2D
Flat shapes like squares, circles, and
triangles are a part of flat geometry and are called 2D shapes. 2D
shapes are shapes with two dimensions, such as width and height.
An example of a 2D shape is a rectangle or a circle. 2D shapes are
flat and cannot be physically held, because they have no depth; a
2D shape is completely flat.

*3D
Solid objects are also known as 3D objects having the
third dimension of height or depth. 3D (or 3-D) means three-
dimensional, or having three dimensions. For example, a box is
three-dimensional; it is solid, and not thin like a piece of paper.
The three dimensions are often called length (or depth), width
(or breadth), and height.

WHAT IS TOLERANCE?
We Can’t Do A Product 100% Exact Size But We Can Very Close The
Size. The Difference Between The Maximum And Minimum Dimensions Of
Permissible Errors Is Called The "Tolerance." The Allowable Range Of Errors
Prescribed By Law, Such As With Industrial Standards, Can Also Be Referred To
As Tolerance.

INDIVIDUAL
(No Datum
Reference)
INDIVIDUAL
or RELATED
FEATURES
RELATED
FEATURES
(Datum
Reference
Required)
GEOMETRIC CHARACTERISTIC CONTROLS
TYPE OF
FEATURE
TYPE OF
TOLERANCE
CHARACTERISTIC SYMBOL
SYMMETRY
FLATNESS
STRAIGHTNESS
CIRCULARITY
CYLINDRICITY
LINE PROFILE
SURFACE PROFILE
PERPENDICULARITY
ANGULARITY
PARALLELISM
CIRCULAR RUNOUT
TOTAL RUNOUT
CONCENTRICITY
POSITION
FORM
PROFILE
ORIENTATION
RUNOUT
LOCATION
14 characteristics that may be controlled

MACHININGPROCESS

MACHININGPROCESS
Machining is a prototyping and manufacturing process that creates a
desired shape by removing unwanted material from a larger piece of material. Since a
part is built by taking away material, this process is also known as subtractive
manufacturing. For information on additive manufacturing

What are different types of machining?
Various machining techniques have been around for decades, but most fall into three principle processes
each requiring a specific tool and experienced machinist.
They are:
•Turning- Turning or Lathing involves rotating the workpiece on a machine, while a single-edged
cutting tool remains stationary. The cutting tool is slowly moved parallel to the workpiece’s rotational
axis, removing material as it goes.
•Drilling - Drilling results in creating a round hole by rotating a cylindrical tool parallel to the
workpiece’s axis of rotation. The hole created is equal in diameter of the tool that was used.
•Milling - Milling is the process of removing material, using rotary cutters, from a workpiece in a feed
motion perpendicular to the rotational axis of the cutting tool. This is one of the most common forms
of machining used today.