Selection principle:
The basic principle to determine the three elements: first determine the amount of back-grabbing according to the cutting requirements, then look up the table to get the feed, and then look up the table to calculate the main cutting speed through the formula.
In many cases, we can determine the value of these three elements through empirical data.
Selection method
Practice has proved that the selection of a reasonable cutting amount is related to many factors such as machine tools, tools, workpieces and processes. The method of reasonably selecting the processing dosage is as follows:
① During rough machining, higher production efficiency should be ensured, so a larger back-grabbing amount, a larger feed amount, and a medium or low cutting speed U should be selected.
②During finishing, it is mainly to ensure the requirements of the size and surface accuracy of the parts, so choose a smaller back-cutting amount, a smaller feed amount, and a higher cutting speed.
③When roughing, it is generally necessary to give full play to the potential of the machine tool and the cutting ability of the tool. When semi-finishing and finishing, the CNC lathe factory should focus on how to ensure the quality of the processing, and on this basis, maximize the productivity. When selecting the cutting amount, the CNC lathe factory should ensure that the tool can complete a part or ensure that the durability of the tool is not less than one work shift, and at least not less than half the working time of the work shift. The specific values ​​of the CNC lathe factory should be selected according to the specifications in the machine tool manual, tool durability and practical experience.

The selection of the amount of back-grabbing: The selection of the amount of back-grabbing should be determined according to the rigidity of the machine tool, fixture and workpiece, and the power of the machine tool. If the process system allows, choose a larger amount of back knife as much as possible. Except for the allowance left for later processes, the remaining rough machining allowance should be cut at one time as much as possible to minimize the number of passes.
Usually on a medium-power machine tool, the back-cutting amount for roughing is 8~10 mm (single side). The semi-finish machining of the CNC lathe factory is 0.5~5 mm; the precision machining is 0.2~1.5 mm.
Determination of the feed rate: When the quality of the workpiece can be guaranteed, in order to improve productivity, a higher feed rate can be selected. When cutting, turning deep holes or finishing turning in CNC lathe factory, it is advisable to choose a lower feed speed. The feed speed should be compatible with the spindle speed and the amount of back tool. When roughing, the selection of feed is limited by cutting force.