Tolerances CNC machining

What is Tolerance in CNC Machining?

Tolerance in CNC machining refers to the degree of deviation allowed from the specified dimensions on an engineering drawing. It defines the exact limits within which a still is considered "acceptable."

As an example, if a shaft is to be 50 mm in diameter, a tolerance of ±0.05 mm may mean that diameters between 49.95 mm and 50.05 mm meet specifications. Tolerances are essential for reliable operation of a product, especially when parts fit together or are used in mechanical systems. The smaller the tolerance, the more accurate the machining – but also the higher the cost, as more accurate machining requires more time and expertise.

How do I determine machining tolerances?

How do I determine machining tolerances?
Determining appropriate tolerances is closely related to the function of the part and the quality requirements of the finished product.
Follow these steps to arrive at appropriate tolerances:

  1. Analyze the application: Determine what role the part plays and how critical the sizing is to its operation.

  2. Identify functional requirements: Look at loads, fit, freedom of movement and safety requirements.

  3. Determine manufacturability: Consider the capabilities and limitations of the production process.

  4. Weigh cost against precision: Tighter tolerances increase cost, so choose high accuracy only where it is really necessary.

  5. Check standards and specifications: Use industry standards as a reference to define realistic and achievable tolerances.

What are typical standard tolerances?

In CNC machining, there are a few commonly used tolerance classes, depending on the precision required: In CNC machining, there are a few commonly used tolerance classes, depending on the precision required:

At Brans Metalworking, we work with tolerances down to ±0.01 mm as standard, but we can also achieve tighter tolerances if the design requires it. At Brans Metalworking, we work with tolerances down to ±0.01 mm as standard, but we can also achieve tighter tolerances if the design requires it.