Before discussing the concentricity of carbide burrs, it’s essential to understand the term first.
When two or multiple objects are concentric or coaxial, it implies they share similar midpoints or axes. Spheres, regular polygons, cylinders, and circles may sometimes be concentric to each other.
In geometry, concentricity has loads of benefits, and this is why experts recommended it. In this post, we will have an in-depth look at concentricity. Moreover, we will also check how this term applies to carbide burrs.
What Is Concentricity?
We can describe concentricity as a unique type of coaxiality. Other than that, concentricity has other explanations, which we will take a quick look at below.
Let’s assume an element that goes through the center of a point. Moreover, it has the axis on a workpiece with a thin wall; the axis measures can be seen as a point. The coaxiality to the datum is often referred to as concentricity.
In other words, concentricity can also be seen as the coincidence in the midpoint of two circles. Total runout and circular turnout are the two different types of runout tolerances. Sometimes, it can be when there’s coaxiality on top of a sphere.
Concentricity can also be defined as the tolerance that tends to hold the central axis feature referenced to a datum axis. In this case, the axes bearing the referenced element are often obtained from the part’s midpoint.
When we talk about geometric dimensioning and tolerancing, concentricity is seen as a 3-Dimensional cylindrical zone. It’s used for the median point of a spherical or a cylindrical part.
When Do We Need to Measure Concentricity?
Measuring concentricity solely depends on the parts you’re working with more often.
You need to measure concentricity when the materials you work with need a very high grade of accuracy. As a result, it helps them function properly.
Thus, if you are using carbide burrs to perform complex tasks, it is a must for you to test the burr’s concentricity. Since carbide burrs are primarily used in dental and industrial applications, concentricity plays a vital role.
It will help if you study them first before making further decisions.
Why is Measuring Concentricity a Complex Process?
Amongst every Geometric Dimensioning and Tolerancing (GD&T) symbol, concentricity can easily be labeled the most tasking one to measure. That’s because you tend to experience difficulties regarding the establishment of feature midpoints.
In measuring concentricity, you must first form the specific datum axis you want to measure. After the datum axis forms, ensure to measure lots of A series in the cross-sections. As soon as the cross-sections are estimated, and you can obtain the required plot of the surface, you can determine the cross-sections’ median point.
Also, note that one must plot these series of points in the cross-sections. Doing this will help you know if they are in the cylindrical tolerance zone. A Coordinate Measuring Machine (CMM) or every other computer measurement system accepts these series’ plots as they can consume a lot of time and costs a ton of money. While measuring concentricity, you must check the accuracy of the two cylinders’ axes.
In the end, concentricity will have some control and only affect the structure and original setup of the feature. It won’t control the oval parts that are perfectly formed but may affect the “D-like” features.
Testing Concentricity of Carbide Burrs With CMM
Let’s check out some of the vital things you should understand about testing concentricity with CMM.
1. Common Axis
The common axis is mainly used when there’s a considerable distance between the datum element and the measuring span. It’s also applicable when both of them are thin-walled.
When testing through the common axis, ensure a virtual connection between the datum element and the measuring element. The point of contact (line) can be called a common axis, and it’s employed as the datum to measure the point of the sphere on both sides.
2. Straightness
Straightness is mainly applicable in workpieces with lots of holes in sequence (ensure that it’s three holes at least) and through holes. Get the circle’s measurement in each of the sections, and leg the centers fit into straight lines. Straightness usually mirrors the concentricity.
3. Maximum Inscribed Circle
The locations of these holes come in varieties, mainly for some of the spots found at long-distance. They also show the midpoint of each of the sections on a similar datum plane. Ensure to attach these midpoints to the maximum inscribed circles. It will help you to ascertain the deviations of the center.
Testing Concentricity of Carbide Burrs With Dial Gauge
First, set your target in a proper position, and keep the dial gauge on the perimeter’s surface for the axis. That indicates its tolerance.
Next, spin the target, and estimate its maximum and minimum runout using a dial indicator. You can also measure The areas of the specified parameters.
If the maximum and minimum difference is significant, then it will be used as the concentricity.
General Formula to Calculate Concentricity
Because of its formula, calculating concentricity is a simple task. However, it’s somewhat challenging to make sure that there’s comprehensiveness between the survey of the tubing wall’s varying thickness.
The first thing to do would be to increase the trials and errors regarding finding the thinnest/thickest thickness. One can use an optical comparator or a micrometer for this purpose.
Accordingly, please note the cross-sections (by marking them with dotted lines) of the thickest and thinnest walls, find the thinnest/thickest points of the wall (tubing) thickness, and measure the consistency that is on the lines using a micrometer.
Finally, create a comparison between the predetermined quality control tolerance and concentricity.
C = (Wmin/Wmax) * 100%
W(min): the minimum width
W(max): the maximum width
From the above formula, “C” is used to indicate percent. So 100% would mean that the tubing is completely concentric. It also means that the wall thickness between the OD and ID is located at similar points close to the diameter in each cross-section.
OD/ID Concentricity and Wall Runout
There are lots of methods of indicating the OD/ID requirements on your drawing. They include:
- Eccentricity percentage
- GD&T concentricity symbol
- Total indicator reading
- OD/ID concentricity
- Runout
Note, wall runout doesn’t only estimate the concentricity. But it also measures the circularity of its parts. Wall runout is obtained from a tube’s eccentricity and describes the wall thickness differences compared to a specific value. In case you are looking for a way to save the cost of proving concentricity and time, you can use the wall runout in place of concentricity.
Here’s the formula for calculating the wall runout:
Wall runout = (Eccentricity) x 2
Where,
Eccentricity = (Max wall thickness) – (Min wall thickness) ÷ 2
What Are The Common Challenges in Measuring Concentricity?
Like we mentioned earlier, it is challenging to measure concentricity and determine if the OD/ID is obtained. Here are some of the requirements of measuring concentricity:
- Getting a lot of measurements across different cross-sections
- Marking the surface and determining where the median points are in the cross-sections
- Plotting the various points and seeing if they are in the cylindrical tolerance zone
You can use an optical comparator or a micrometer to measure the concentricity of certain parts. Nonetheless, employing a CMM is the best way to perform this task.
One other challenge you may encounter is the fact that parts are always smaller, unlike before. For example, checking the concentricity of double diameters in small tubing is a challenge regarding small precision cut tubes.
Concentricity Measurement Video
Below, we will take a look at this clip that shows concentricity measurement.
Final Thoughts!
At this point, you will notice that concentricity indeed has a complex nature. That’s why it’s applicable for just parts that need to function correctly, as it gives a higher level of precision.
For example, the carbide burrs used in dentistry need a very high level of precision. A similar point applies to carbide burrs used in complex engineering projects. That’s why runout is sometimes a preferable method to replace the need for concentricity.
Nevertheless, getting your burrs from a reliable carbide burr manufacturer is the ultimate solution. At FitCarbide, we ensure to provide you with carbide burrs of high concentricity.