Tolerance in CNC Machining

Last Updated on October 13, 2023 by assistant

CNC machining is considered as one of the most high-precision processing ways to create prototypes. But, it doesn’t mean that it can ensure the accuracy of every prototype. And different CNC machining project get unique requirements on tolerance. There are several factors which may affect the tolerance of the prototype in the process of CNC machining.

Figure1 Custom Precision Machining


The common CNC machines on the market include 3/4/5-axis CNC machines. The more axis for machining, the more accurate the prototypes will be We could hardly use the 3-axis CNC machine to create an aluminum part with the tolerance down to 0.002mm.


Different materials have unique strength and thermal stability. The material you choose will greatly affect the tolerance of the machined prototypes. For example, compared to metal, the tolerance of plastic is not less tight. The plastic is easier to warp.

CNC Machined PMMA PartsCNC Machined ABS Parts

3.Surface Treatment

After machining, most people would choose various kinds of surface treatment for their machined prototypes. They will make these parts look more decorative and durable. But, it may affect the tolerance of these parts.

Anodizing for Aluminum Parts

Anodizing is one of the common surface finishes for CNC aluminum machined parts. After anodizing, it will form a more durable oxide film on the surface of the aluminum parts. If that film is too thick, it will affect its tolerance.

At Ruitai, to meet your demand on tolerance, we will inform you before anodizing. If yes, we will anodize the parts according to your requirement.


During the process of assembling, we may need to assembly the different metal machined parts. It means that these machined prototypes should be as accurate as the 3D/2D drawings show. It requires highly on the accuracy of these parts. If not, they can’t be assembled successfully.

Before machining, we often suggest out clients to offer us both the 3D and 2D files to avoid that kind of mistake. In some cases, some clients would send us some parts in advance. And we are responsible for creating the rest of the parts and assembling the whole parts.

How Do We Maintain Tolerances on Machined Parts?

Ensuring tight tolerances has always been one of our working standards. To meet different requirements on the tolerance of CNC machining, we get 3/4/5-axis CNC machines available.

Except for that, quality control is also an important step in ensuring tolerability. Without this step, we can’t know if the parts are up to standard before we ship them to you. In order to achieve this goal, we have established a complete quality inspection team to conduct multiple quality inspections on the processed parts.

We usually use coordinate measuring machines, vernier calipers, height gauges, etc. Different tools have different measurement methods. Among them, the most convenient is the vernier caliper. We can hold it to measure the actual data of parts from different angles.


To further ensure tolerances, we typically choose CMM equipment. Its touch probes test the size and shape of parts along the X, Y and Z axes. By measuring several points, we will get their final data.

If you want to know more details about how we control the tolerance for your machining project, contact us here.