A CNC Machining Accuracy Guide for You To Learn More About It

It is all about precision in the world of CNC machining. A CNC machine might produce a gear that is about half a millimeter smaller or bigger than needed. These tiny changes cause an unimaginable disruption to quality of the outcome. This is where there is a need for high precision in CNC machining.

This blog will take us on to the world of CNC machining accuracy, looking at its types, what affects it and how important it is in sectors like aerospace, automotive and medical industry. Let’s have a look at the precise world of computer numerical control (CNC) machining.

Table of Contents

What is CNC machining accuracy? 

Machining accuracy in CNC machine tool machining is merely a way by which what should be machined on paper actually gets done. A measuring game for parts. In addition, this kind of accuracy is very vital for diverse industries like medical and others as this has a direct consequence to quality.

Let’s say you require a tooth that is actually fifty-millimeter wide. However, if the CNC machine is not highly accurate, then this gear may have turned out to measure only 49.8 or 50.2mm – slightly undersized or oversized. However, such little variation may cause misfitting it into other parts of the device thereby distorting everything.

We employ very small units such as micron or millimeter to measure this level of accuracy. This is done using micrometers or machine tools of measurement (CMM). So, as we run a comparison of these measurements with our plans and how everything is set, we find out whether we are moving in the right direction.

The type of CNC machining accuracy

Positional Accuracy:

This is a term that means, precision of stopping at a required point for moving machine or equipment. Positional accuracy is usually expressed in terms of micrometers (or millimeters)..’


Accordingly, repeatability means that the machine can hit a similar place when machining a single component over and over again. It is most often also given in units of micrometers or millimeters.

Profile Accuracy:

They include profile accuracy, which emphasizes that the dimensions of such a part be exact regarding contours and shape. For example, parts with high precision in shape.

Surface Roughness:

This is concerned with how rough a given machined component’s surface will be post-processing. The surface roughness is usually much lower and a higher level of precision is therefore needed.

Dimensional Accuracy:

By dimensional accuracy, it means the difference between the dimensions of an actual part against the designed dimensions. It usually represents a distance of a micrometer or a millimeter.

Angular Accuracy:

One of the most essential specifications in angle-sensitive components is angular accuracy. Aspects of this include angular cutting and positional accuracy.

Factors affecting CNC machining accuracy: 

Machine Calibration

Machine calibration is one of the things that affect CNC machining accuracy. Machine calibration influences the dimensional and shape precision of parts made. For instance, defective mountings of the machine’s guideways and their deterioration can cause errors in positioning the workpiece. It therefore means that calibrating machines on a regular basis is critical in making CNC machining accurate.

Tool Wear

They include tool wear and other factors. With time, machines become dull resulting in poor surface finish and dimensional variations on the workpieces. For example, worn-out tools will be capable of scuffing or creating chips on the workpiece. It means that worn out, severely worn tools should be replaced on time if you want to ensure the machining accuracy.

Material Properties

Also, some of the most important considerations for this include material properties. Hardness, thermal expansion coefficient, and cutting properties depend on the material in question. Likewise, aluminum alloy materials do not have the same characteristics as steel, resulting in different machining parameters and tools for attaining a certain degree of precision.


The last and very important element that characterizes CNC machining is programming. There may be workpiece deviations due to programming errors or the lack of correct machining code. Likewise, during machining, if there is even a slight variance or coordinate error in the set machining program, the workpiece can be cut out. As such, high-precision programming as well as verification ensure CNC machining precision.

What is the difference in CNC machining accuracy and tolerances?

The accuracy and tolerances of CNC machines are important considerations in the industrial engineering sector. Accuracy is generally associated with the degree of consistency between measurements that are required by the dimensions of a part relative to the specifications of its design. Accuracy should be as high as possible, because the closer the part is to the design specifications, the better the quality and precision of the part.

On the other hand, tolerances mean an acceptable range of size fluctuation or deviation during the part-making processes. That is, it shows the acceptability range of dimensional variations when manufacturing a specific object. Numerical values are usually specified for tolerances in machining standards/specifications.} For instance, a tolerance may be indicated as “+.005mm, – .005 mm”, meaning that the dimensions of the component should differ from the design requirements in – .005 mm and + .005 mm respectively.

Therefore, accuracy considers the comparison between the actual dimensions of the part and its design dimensions and tolerances to determine the acceptable variation of dimensions.

Methods to Improve Accuracy: 

Regular maintenance is vital. Maintaining a clean machine that also lubricates the bearings and guideways is done to improve the machining accuracy which comes with keeping the system in an optimal working state. Accuracy must also be ensured through periodic inspection of worn-out items such as cutting tools and tool holders. This eliminates mistakes attributable to friction.

Better cutting tools and tooling play a major role in achieving accurate CNC machining. Use of appropriate cutting edges and cutters which have minimal vibrations also increases the quality of the cutting surface. Also, using good quality fixtures and clamping devices helps to have a firm grip on the workpiece thus reducing the chances of making mistakes.

The accuracy in machining can as well be enhanced by employing advanced programming techniques. CAD/CAMP software provides specific process plans that minimize mistakes and errors. Also, the understanding of G-code programming as well as CNC controller functions will enable the right execution of the programs.

CNC machining accuracy measures: 

Checking various inspection techniques and instruments guarantees that components are exactly right. For example, they comprise coordinating machine measuring tools such as projectors, micrometers, and microscopes (among many others). The tools are used for measuring the length, shape, and quality of surfaces. Furthermore, several non-contact detection processes including laser detection and optical scan are also able to offer great precision.

Thorough testing and inspection guarantees the accuracy of CNC machined part, satisfy customers’ demand, and improve product quality. The above-discussed tools and procedures are central in quality control measures meant to guarantee precision, and reliability of the CNC machined items done.

Comparison of the accuracy of CNC machining 3D print

AspectCNC Machining3D Printing
AccuracyHigh precisionModerate precision
ToleranceVery tightLimited tolerance
Material CompatibilityWide range of materialsLimited materials
SpeedSlower for complex shapesFaster for simple shapes
Surface FinishExcellent finishLayered appearance
Setup and Lead TimeLonger setup, longer lead timesShorter setup, shorter lead times
CostHigher initial costLower initial cost
Prototyping CapabilityLimited for rapid prototypingGreat for rapid prototyping
Complexity of DesignsSuitable for complex, intricate partsLimited complexity
Post-processing RequiredMinimal post-processingMay require post-processing

The importance of CNC machining accuracy in some Industry Applications: 

The airline industry, for example, places great emphasis on high precision quality of the products made by means of CNC machining. Small errors in space are destructive; precision CNC machining is essential for parts of engines, control systems, and crucial units.

Engine, drivetrain, and brake components in the automotive industry rely on high CNC machining accuracies to satisfy highly stringent specifications, ensuring optimized car performance and security.

Precision is one attribute that stands out in medical device manufacturing because it has an effect on patients’ lives and health. Precision and reliability in numerous varieties of medicine are dependent on CNC machining.

Benefits of high CNC accuracy: 

There are many reasons why high precision is important in manufacturing products. Secondly, high-precision product manufacture may largely enhance the product’s performance. This is vital as it can help ensure that the sizes and figures of parts remain in conformity with those provided in the prescribed limit of accuracy so that a product performs its designated role correctly. Its aim is to ensure that the quality of the product improves it useful life span and also reduce product maintenance cost.

In addition, high precision is equally important in the assembling process of products. Inaccurate sizing and shape in parts will make assembling unbearable or fail due to tolerances. Precise, high-level manufacturing makes it easy for all parts to fit with one another and boosts productivity and efficiency in production. They also affect precision during manufacture. These lead to performance as well as the finished goods’ quality.


Precision is a key aspect of CNC machining. However, it goes beyond adherence to designs and ensures safety in aviation, optimization of automotive, and improvement of medical devices.The importance of regular maintenance, advanced programming, and minute inspection techniques. Unlike 3D printing, CNC machining is much more precise providing better finishes and tight tolerances.

The advantages are clear: enhanced product operations, efficient joining/bonding process, and reduced costs over time. What makes precision so important? It is the road from good to great. Call our precision CNC machining specialists for a consultation to let it rip. Accuracy is what we live for, nudging you through endless opportunities.


On-demand CNC Machining prototyping and parts with Custom Finishes and low volume manufacturing.

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