5 things you need to know about OD/ID concentricity

1. What is concentricity?

Concentricity is complex - a "circular symmetry" used to establish tolerance zones for the median points of cylindrical or spherical parts.

Concentricity can be defined as a measure of the thickness constancy of a tube, pipe, or other cylinder.

If the concentricity is "perfect", then the wall thickness between the outer diameter and the inner diameter is the same at every cross section, at every point around the diameter of the tube.

2. When concentricity is needed

Concentricity is usually only used for parts that require very high precision to work properly.

However, even if concentricity is not important, it may be important to know how far OD/ID can deviate from concentricity.

3. OD/ID concentricity labeling

Pipe od/OD concentricity requirements can be indicated on drawings in several different ways.

GD&T concentricity symbol

Eccentricity percentage

TIR (Total indicator Reading)

A written statement

4. The challenge of measuring concentricity

Measurement needs:

Multiple measurements are made on a series of cross sections

Draw the surface and determine the median points for all cross sections

Plot points to see if they fall within the cylindrical tolerance area

Another challenge is that in today's micromachining, the parts to be measured are often smaller than ever before.

5. Alternative: Heart rate and beat

In some cases, you can avoid the time and cost of verifying concentricity by replacing the concentricity requirement with runtimes, which are easier to measure and easier to implement.

The beat is a combination of concentricity and roundness - if a part is perfectly round, the beat will equal concentricity.

Design tubing with achievable tolerances in mind

Remember that the feasibility of producing parts within acceptable tolerances is a critical consideration when drawing.

This is why most mechanics, measurement technicians, and design engineers recommend avoiding OD/ID concentricity whenever possible.

Please contact us at zhang@pride-cnc.com