The machining accuracy of Turning, Milling, Planing, Grinding, Drilling, and Boring (2024)

Machining accuracy is mainly used to characterize the fineness of products, and it is a term to evaluate the geometric parameters of the machined surface. Machining accuracy is measured by tolerance grade. The smaller the grade value, the higher the accuracy.

There are 20 tolerance grades from IT01, IT0, IT 1, IT 2, IT 3 to IT18. IT01 represents the highest machining accuracy, and it18 represents the lowest machining accuracy. The spare parts of mining machinery should reach it7, and agricultural machinery should reach it8. According to the different functions of product parts, the processing precision is different. The machining accuracy is decided by turning, milling, planing, grinding, drilling, and boring.

1. Turning

Turning is generally performed on a lathe to process the inner and outer cylindrical surfaces, end surfaces, conical surfaces, forming surfaces, and threads of the workpiece. The turning precision is generally IT8-IT7, and the surface roughness is 1.6-0.8μm.

2. Milling

Milling is used to processing planes, grooves, various forming surfaces (such as splines, gears and threads) and special shapes of molds. According to the same or opposite direction of the main movement speed and workpiece feed direction during milling, it is divided into down milling and up milling. The machining accuracy of milling is generally up to IT8-IT7, and the surface roughness is 6.3-1.6μm.

3. Planing

It is mainly used for the shape processing of parts. The machining accuracy of planing can generally reach IT9-IT7, and the surface roughness is Ra6.3-1.6μm.

4. Grinding

It belongs to finishing and is widely used in the machinery manufacturing industry. Grinding is usually used for semi-finishing and finishing, and the precision can reach IT8-IT5 or even higher. The surface roughness is generally 1.25-0.16μm.

5. Drilling

Drilling is often carried out on drilling machines and lathes, but also on boring machines or milling machines. The machining accuracy of drilling is relatively low, generally only reaching IT10, and the surface roughness is generally 12.5-6.3μm. After drilling, reaming and reaming are often used for semi-finishing and finishing.

6. Boring

Boring is an inner diameter cutting process that uses tools to expand holes or other circular contours. Its application range generally ranges from semi-rough machining to finishing. The tools used are usually single-edged boring tools (called boring bars).

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See Also

Differences Between Turning vs Grinding vs Milling