Common Tolerances on CNC Lathes

1. Tolerances:

Tolerances on CNC lathes refer to the allowable deviation range between the shape and position of the part during the machining process and the design requirements. Tolerances consist of shape tolerances and positional tolerances. Shape tolerances refer to the shape deviations between different parts of the part, such as straightness, roundness, cylindricity, etc. Positional tolerances refer to the positional deviations between different parts of the part, such as parallelism, perpendicularity, coaxiality, etc. CNC lathes achieve high-precision tolerances by controlling tool motion trajectories and machining parameters, ensuring the quality and accuracy of the parts.

FEATURES	TYPE OF TOLERANCE	CHARACTERISTIC	SYMBOL
FOR INDIVIDUAL FEATURES	FORM	STRAIGHTNESS
		FLATNESS
		CIRCULARITY(ROUNDNESS)
		CYLINDRICITY
FOR INDIVIDUAL OR RELATED FEATURES	PROFILE	PROFILE OF A LINE
		PROFILE OF A SURFACE
FOR RELATED FEATURES	ORIENTATION	ANGULARITY
		PERPENDICULARITY
		PARALLELISM
	LOCATION	POSITION
		CONCENTRICITY
		SYMMETRY
	RUNOUT	CIRCULAR RUNOUT
		TOTAL RUNOUT

2. Shape Tolerances: Roundness and Cylindricity

2.1 Roundness: The deviation of the part surface from the ideal circular shape. CNC lathes achieve the required roundness tolerance by controlling tool motion trajectories precisely during the machining process.

2.2 Cylindricity: The deviation of the diameter along the axis of the part. CNC lathes ensure consistency of the diameter during the machining process to meet the required cylindricity tolerance.

3. Position Tolerances: Concentricity and Coaxiality

3.1 Concentricity: Refers to the deviation between two axes. CNC lathes ensure the relative positional accuracy between different axes by precisely controlling the positions of the tool and workpiece, meeting the design requirements for concentricity tolerance.

3.2 Coaxiality: Refers to the deviation between the center of the bore and the outer surface. CNC lathes ensure alignment between the center of the bore and the outer surface by accurately controlling the positions of the tool and workpiece, meeting the design requirements for coaxiality tolerance.

4. Methods to Reduce Position Tolerances:

4.1 Precise Control of Tool Paths: By optimizing CNC programs, ensure that the tool maintains a stable trajectory during the machining process, minimizing trajectory deviations.

4.2 Use of High-Precision Fixtures: Employ precision fixtures to clamp workpieces, ensuring stable positioning during machining, reducing vibrations and offsets.

4.3 Regular Equipment Maintenance: Maintain CNC lathe equipment in good condition, regularly inspect and maintain various components of the machine tool, ensuring smooth equipment operation, and reducing machining errors.

4.4 Accurate Measurement and Calibration: Use high-precision measurement tools to inspect machined parts, promptly detect deviations, and make adjustments and calibrations to ensure that concentricity meets design requirements.

4.5 Selection of High-Precision Cutting Tools: Choose high-quality, rigid cutting tools to reduce vibrations and deformations during cutting processes, improving machining accuracy.

4.6 Optimization of Machining Parameters: Adjust machining parameters such as cutting speed, feed rate, and depth of cut to minimize deformations and deviations during the machining process.