Points to Remember When Selecting Machine Tolerances


CNC machining is known to produce machined parts with very high precision. Different parts have different precision levels meaning the tolerance level in each varies. What are tolerances? They are measurements done to indicate the precision level of a machined part. During the machining process, the part’s dimensions may be slightly smaller or bigger than what was designed. But how big or small is the variation? This is where machining tolerances come in. In this post, we discuss things to note when selecting machining tolerances.

Tips to consider when choosing machining tolerances

Tolerances signify the degree of variation allowed, but it does not apply to all machined parts. Engine components must be of high precision, and no variation is permitted. However, we cannot do away with the idea that variations are common during machining. So what must you remember before choosing a tolerance?

1. The kind of tolerance you need

In some instances, the entire part needs to adhere to the given tolerance, while only specific features are affected by it in others. There are two forms of tolerances; tight and loose tolerance. Tighter tolerances are known to be small, while the looser tolerance is large. If you want more precision on a machined part, then a tighter tolerance is ideal. A looser tolerance indicates less accuracy of a machined part. The precision level for structural points must be high as they are designed to fit in components like holes.  Tolerances give you an idea of how a particular machined part will function. It’s necessary to involve the manufacturer and notify them of the kind of tolerance you want for your parts

2. Tolerance effect on the part cost 

Tolerances directly impact a machined part’s quality, and by so doing, it influences the cost of producing the piece. Typically, a high-quality product is more expensive than that of lower quality. Similarly, higher tolerances cost more than lower tolerances as machining involves pricey tools and more time. Higher precision parts, meaning a tight tolerance is involved, cost more than those with low precision. This is because there is minimal room for errors, and extensive testing and inspection must be conducted. The rate of failure in high tolerance machining is high, meaning the cost of producing the machined parts

3. Choice of material

The material you pick determines the kind of tolerance you’ll use. Achieving high tolerance for some materials is difficult, while it is easy for others. This is determined by various characteristics of each material, such as stability when exposed to heat, hardness, and abrasiveness. When you subject non-metals to heat, they deform with time; hence it is difficult to use tight tolerances on them. Also, machining soft materials to tight tolerances is hard as they tend to move a lot. Rough materials damage the state of the tool resulting in less precise parts.

Last words

Use the tips above to help you pick the right machining tolerance for your parts. Generally, machined parts have high precision, but there are instances where slight variations come in. Determine the parts you want, then consider the type of tolerance you need based on the material. Additionally, identify how your tolerance selection will affect the cost of production. 

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Margareta is a journalist who has dedicated her life to informing the public about news updates from around the world. She believes that it's important for people to be educated about various topics, like healthcare or crime prevention, so that they can have productive conversations and make informed decisions. Margareta also loves sharing shopping tips with her readers, because she believes that everyone should be able to afford high-quality products without breaking the bank.


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