To calculate taper (an inclined or tapered workpiece surface) on a CNC lathe, you need to know the following parameters:

1. Workpiece length (L): The distance between the starting and ending points of the workpiece at the desired taper.

2. Workpiece Diameter (D1 and D2): The diameter of the workpiece at the starting and ending points.

3. Taper Angle (α): The required taper angle, usually expressed in degrees.

The taper can be calculated using the following formula:

tan(α) = (D2 - D1) / L

From the known workpiece diameter difference and workpiece length, the inverse tangent function (tan-1) can be used to calculate the taper angle (α).

NOTE: When calculating taper, convert length and diameter to the same units (for example, millimeters or inches) to maintain consistency.

Please note that this is a simplified calculation method, which is suitable for cases with small taper angles or short taper lengths. In practical applications, there are some other factors to consider, such as the accuracy and stability of the lathe, the characteristics of the workpiece material, etc. It is recommended that in practical applications, refer to the operating manual of the CNC lathe or consult professionals for more accurate calculation methods and suggestions.