How do you call flatness on a drawing?

Flatness on Drawings Use of Flatness in a drawing is straightforward. Simply callout the Flatness allowance in a feature control frame with an arrow leader designating the surface being controlled. The Flatness feature control frame may also rest on an extension line for a dimension of the surface.

What is flatness in drawing?

Flatness is a measure of a surface’s form compared against itself, indicating that all the points along the surface lie in the same plane. Symbolized in GD by a parallelogram, flatness allows you to limit waviness or variation in a surface without tightening its dimensional tolerance.

How do you specify surface flatness?

Flatness is can be measured using a height gauge run across the surface of the part if only the reference feature is held parallel. You are trying making sure that any point along the surface does not go above or below the tolerance zone.

What is the difference between surface finish and flatness?

Flatness is a macro-level measurement while surface finish is a micro-level measurement. Flatness may have a large impact on fit and function, while surface finish is more typically function than fit.

What flatness means?

flatness noun [U] (LEVEL QUALITY) the quality of being level and without curved, high, or hollow parts: The flatness of the desert was broken only by a few large piles of rocks. SMART Vocabulary: related words and phrases. Straight, even and level. be (as) flat as a pancake idiom.

How do you evaluate flatness?

When measuring flatness, you are checking for unevenness in the surface, to see how precisely flat a surface is. The most protruding part and the most concaved part must be at a specific distance between two planes that are separated vertically. The Easiest Way to Measure Flatness.

What are three methods of checking a filed flat surface?

Flatness testing Methods

  • Using Two footed twisting Gauge/Three footed twisting Gauge.
  • Spirit Level Method.
  • Auto Collimator.
  • Beam Comparator.
  • Laser Beam.
  • Comparing with Liquid surface.
  • Interference Method.

What is the unit of flatness?

I-Units is an exacting quantitative flatness measurement. It is a dimensionless number that incorporates both the height (H) and peak to peak length (L, or P in the diagram below) of a repeating wave. For example: a sheet with a 1/16” high wave which repeats every 12” would have an I-Unit value of 6.7.

What is a normal flatness tolerance?

A flatness control is applied to the top surface. We know that the flatness applies to the surface because the flatness control points to the top surface. The flatness tolerance zone is two parallel planes 0.1 mm apart. The size can never be greater than 31 or less than 29.