Menu

SMLease Design

Mechanical Product Design & Development Partner

Flatness : GD&T Tips SMLease Design

  • Flatness is a condition that defines the flatness of a surface regardless of any datum feature.
  • Flatness is used to make use required surface is flat without tightening any other dimension.
  • Value of Flatness tolerance is always less than the dimensional tolerance associated with a part feature.
  • No Datum Plane is required.
  • LMC and MMC can be used.

Flatness Representation


Tolerance Zone

Reference surface should lie in between two parallel planes


 

Where Flatness Is Used

If the requirement is to make highlighted surface flat within 0.1 mm limit.  Without Flatness Tolerance one way to do this is : reduce the tolerance limit for thickness.

But this will increase overall manufacturing cost. To avoid this we increase the tolerance in thickness and add flatness tolerance as per requirement.

 


 

 

Flatness  tolerance with increased value of tolerance value in thickness.

 

In order to achieve same value of  flatness without flatness tolerance we need reduce tolerance in thickness

 

 


Related Articles

Straightness

Concentricity

Circularity

Cylindricity

Parallelism

Angularity

Symmetry

 

Perpendicularity

MMC

LMC

Profile Of Surface Control

Profile Of Line Control

Go Back

Comment

Submit

Latest Posts

Page Counter

347145