What Is the Maximum Machining Accuracy of a Machine Tool?

The highest precision and various tolerance levels achievable by machine tools such as turning, milling, planing, grinding, drilling, and boring are detailed below.

Turning

Turning involves the rotation of a workpiece while a cutting tool moves linearly or along a curved path within a plane. Typically performed on a lathe, turning is used to machine internal and external cylindrical surfaces, faces, conical surfaces, shaped surfaces, and threads.

The precision of turning generally ranges from IT8 to IT7, with surface roughness ranging from 1.6 to 0.8μm.

1. Rough turning aims to improve turning efficiency by using large cutting depths and feed rates without reducing cutting speed, achieving a precision level of IT11 with a surface roughness of Rα20~10μm.

2. Semi-finish and finish turning utilize high speeds and relatively smaller feed rates and cutting depths, achieving precision levels from IT10 to IT7, with surface roughness ranging from Rα10~0.16μm.

3. High-precision turning on specialized machines with finely honed diamond tools can achieve precision levels from IT7 to IT5, with surface roughness ranging from Rα0.04~0.01μm, referred to as "mirror turning."

Milling

Milling involves using rotating multi-edge cutting tools to remove material from the workpiece, providing an efficient method for machining flat surfaces, slots, various contours, and specialized forms such as gears and threads.

Milling precision typically ranges from IT8 to IT7, with surface roughness ranging from 6.3 to 1.6μm.

1. Rough milling achieves precision levels from IT11 to IT13, with surface roughness ranging from 5 to 20μm.

2. Semi-finish milling achieves precision levels from IT8 to IT11, with surface roughness ranging from 2.5 to 10μm.

3. Finish milling achieves precision levels from IT16 to IT8, with surface roughness ranging from 0.63 to 5μm.

Planing

Planing involves using a planer blade for horizontal reciprocating cutting motion, primarily used for shaping the external profile of components.

Planing precision generally ranges from IT9 to IT7, with surface roughness ranging from Ra6.3~1.6μm.

1. Rough planing achieves precision levels from IT12 to IT11, with surface roughness ranging from 25 to 12.5μm.

2. Semi-finish planing achieves precision levels from IT10 to IT9, with surface roughness ranging from 6.2 to 3.2μm.

3. Finish planing achieves precision levels from IT8 to IT7, with surface roughness ranging from 3.2 to 1.6μm.

Grinding

Grinding involves using abrasive materials and tools to remove excess material from the workpiece, commonly used for precision machining in various industries.

Grinding is typically used for semi-finish and finish machining, with precision levels ranging from IT8 to IT5 or higher, and surface roughness ranging from 1.25 to 0.16μm.

1. Precision grinding achieves surface roughness from 0.16 to 0.04μm.

2. Ultra-precision grinding achieves surface roughness from 0.04 to 0.01μm.

3. Mirror grinding achieves surface roughness below 0.01μm.

Drilling

Drilling is a fundamental method for hole machining, commonly performed on drilling machines, lathes, and other machining centers.

Drilling precision is relatively lower, typically reaching IT10, with surface roughness ranging from 12.5 to 6.3μm, often followed by reaming and tapping for semi-finish and finish machining.

Boring

Boring is a cutting process used to enlarge holes or shape circular profiles, covering a range of applications from semi-rough to precision machining.

1. Boring precision for steel materials generally ranges from IT9 to IT7, with surface roughness ranging from 2.5 to 0.16μm.

2. Precision boring achieves precision levels from IT7 to IT6, with surface roughness ranging from 0.63 to 0.08μm.

Note: Precision machining is crucial for assessing the fine details of manufactured products, with tolerance levels ranging from IT01 to IT18. Machinery typically falls within IT7 for industrial equipment and IT8 for agricultural machinery. The required precision varies depending on the component's function, influencing the choice of machining processes and techniques.