Understanding Accuracy, Precision, and Tolerance of CNC Machining


There are certain technical terms that we use, however, do not know their exact meaning, or why are they used. There are so many technical terms associated with the specifications and capabilities of the CNC machining. Do you know the meaning of each and every term? While buying CNC machining service from a service provider, you must have heard or read some terms like accuracy, tolerance, precision, and so on. What do these terms denote? The following post will give you a clear idea of the three terms – accuracy, precision, and tolerance.

1. What is Accuracy in Machining?

Accuracy refers to the difference between the actual measurement and measurement from your system. The accuracy of that measurement is said to be high when the difference between the two is extremely less. It is also referred to as the degree of conformity. Let’s consider an example to make it a bit easier to understand. You go to a CNC machining service provider and they say that the CNC machine tools they have are highly accurate. This means that if their tools are programmed for cutting a metal piece, which is 50 mm in length, then the tool will cut the piece exactly. If the tool is really accurate as the service provider says, then it will get closer to 50 mm, without any errors.

2. What Do You Mean by Precision?

This is another most important term that is used in CNC machining, and this term defines the reliability of a machine tool. Basically, precision is a measure, which defines the capability of a measurement system to return the same measure again and again. You can call it repeatability of the measurement system. Therefore, if you are looking forward to getting reliable information, which you can use for your further calculations, then you have to ensure good repeatability of the system. Besides this, it is very important for a measurement system to be both accurate, as well as precise.

3. What Does Tolerance Mean in Machining?

Last, but also the important – tolerance. The term tolerance can be defined as the allowable or predictable deviation of the measurement system from the known or standard value. The tolerance of any system is usually expressed as “+/-”. Let us consider an example, to explain this concept clearly. If a CNC machining tool has a tolerance of +/- 0.01 mm, the machining tool can introduce a deviation of 0.01 mm in every cut. This deviation can be either 0.01 mm extra than the standard value, or less than 0.01 mm by the standard value.

We hope you got an understanding of the terms – accuracy, precision, and tolerance used in CNC machining. This understanding of terms will make you more confident while communicating with manufacturers such as Takam Machinery. It will also help you to understand all the important specifications and capabilities, and compare them with your requirements.