Concentricity Facts Every Machinist Should Know

Those who spend enough time in the machining industry will eventually encounter the term “concentricity.”  This term refers to geometric dimensions and tolerancing.  Concentricity is a tolerance similar to a circular symmetry that creates a tolerance zone for spherical or cylindrical median points.  Let’s take a closer look at this term and its importance in practical terms.

 

Concentricity has the Potential to Prove Quite Helpful for Specific Machining Projects

Concentricity is useful when parts mandate a high level of precision for functionality.  For example, concentricity has to line up with the ID and OD for tubes to enter an opening when a separate part must fit within the tube ID.  However, even if concentricity is not of the utmost importance, it can prove helpful to know the extent to which the ID/OD is out of concentric. 

 

For example, consider a situation in which gasses or liquids are moving into a tube when pressure is applied.  The bare minimum of wall thickness must be specified to guarantee the load does not lead to a break in the non-concentric wall of the tube. This process is just one example of how concentricity is used.

 

Perfect Concentricity is Possible

Perfect concentricity exists when the thickness of the wall between the ID and OD is the same in each cross-section.  However, for there to be genuinely ideal concentricity, the thickness between the ID and OD has to be the same at all points across the tube diameter.

 

Concentricity is Distinct From Cylindricity

Concentricity is not the same as cylindricity.  Cylindricity refers to the level of roundness as well as straightness at a three-dimensional part’s full axis.  Alternatively, concentricity compares an ID and OD.  Furthermore, concentricity can also compare roundness at specific points.  In short, concentricity is defined as a measure of a pipe, tube, or another cylinder’s wall thickness constancy. This means concentricity controls the centralized axis from the part’s median points in the context of cross-sections.

 

Why Concentricity is Uber-complex

Tubing concentricity is particularly complex as it is based on measurements taken from a derived axis rather than a surface that can be touched with the hand.  As a result, theoretical three-dimensional cylindrical tolerance zones develop where the tube’s derived median points fall.  Therefore, concentricity is typically used with high-precision parts in which the median points must be controlled.

 

Concentricity is not the Same as Eccentricity

Eccentric tubes are those in which there are differences in the thickness of tube walls.  This occurs when the circle created by the OD has a center with a different point than that of the middle of the center created by the ID. 

 

This means the circles lack concentricity.  A cross-section is examined to gauge the maximum and minimum dimensions of the tube walls to measure eccentricity.  The difference between the maximum and minimum girths is calculated and subsequently divided in half to determine eccentricity.

 

Measuring Concentricity is Inherently Challenging

Concentricity is challenging to measure as it is quite challenging to determine the central axis that functions as a reference point.  Furthermore, gauging concentricity requires taking measurements across several cross-sections and mapping the surface to pinpoint the cross-sections’ median spots. 

 

Furthermore, these points must be plotted to determine if they are in the cylindrical zone of tolerance.  A coordinate measuring machine or a specialized computer program is necessary to measure concentricity accurately.

 

Contact Laurel Wire Company Today

Reach out to us today to learn more about our wire straightening and wire cutting services.  Our services are considered the best in the industry.  Our offerings include cutting round wire and flat wire along with strip material from the coil’s form. 

 

You can reach our customer service team by dialing (800) 783-9473.  If you prefer to contact us online, fill out our online contact form and we’ll happily assist you!