Gun Drilling How to choose cutting parameters

The cutting amount of gun drilling refers to the cutting speed v and the feed rate f.

The cutting speed here refers to the linear speed of the outer circle of the tool in m/min, and the conversion of the spindle rotational speed in rpm is shown in the following formula; f refers to the feed rate of the tool in one revolution mm/rev , which is related to the frequently encountered feed speed F ( mm/min) is calculated as follows:

The cutting amount in the gun drilling process is mainly restricted by the chip formation state, which is related to factors such as the diameter of the gun drill, the material of the workpiece and its physical and mechanical properties, the material of the cutting edge of the tool, the cutting fluid, and the geometric parameters used for the cutting edge of the gun drill head. Direct relationship.

1

Gun drill diameter

The larger the diameter of the gun drill, the higher the feed rate. However, the cutting speed is generally not affected by the diameter of the tool. The smaller the tool diameter, the higher the speed of the tool spindle, and the larger the diameter of the tool, the lower the speed of the tool spindle.

2

Workpiece material and its physical and mechanical properties

The cutting performance of different workpiece materials is different, even if the same material is in different heat treatment states, the cutting performance is also very different. It mainly affects the cutting speed, and secondly affects the feed rate.

The better the machinability of the workpiece material, the higher the cutting speed v and the larger the feed rate f; the worse the cutting performance of the material, the smaller the cutting speed v and the feed rate f.

3

Tool cutting edge material

At present, the cutting edge material used to manufacture gun drills is mainly cemented carbide. Different grades of cemented carbide should be selected according to the supplied material and its mechanical properties, so as to ensure the improvement of processing quality and achieve the ideal cutting efficiency.

The improvement of tool materials is mainly reflected in the increase of cutting speed, increase of spindle speed and feed rate per minute.

The types of hard alloys commonly used in deep hole tools are mainly P, K, and M.

P-type cemented carbide is often used for processing carbon steel, low alloy steel, high alloy steel and cast steel.

K-type cemented carbide is commonly used in processing cast iron (gray cast iron, ductile iron, malleable cast iron), non-ferrous metals and non-metallic, ferritic and martensitic stainless steels.

M-type cemented carbides are often used for processing austenitic steel, manganese steel, cast iron, non-ferrous metals and non-metallic, ferritic and martensitic stainless steels.

4

cutting oil

Cutting oil has three functions of lubricating, cooling and chip removal. Due to the characteristics of the gun drilling process, a reasonable supply of cutting oil is particularly important.

First of all, the machine tool system must have a complete cutting oil supply system to ensure sufficient cutting oil supply pressure and flow.

The smaller the hole diameter, the higher the oil pressure of the cutting oil required , and the larger the flow rate, the corresponding decrease; the larger the hole diameter, the lower the oil pressure of the cutting oil required , and the greater the flow rate. The larger the depth-to-diameter ratio to be processed, the greater the oil pressure required.

Generally speaking, when the diameter of the drilling hole is less than 2.0mm, the oil supply volume of the oil pump is not less than 4 L/min; when the diameter of the drilling hole is 2.0-12.0mm, the oil supply volume of the oil pump is not less than 24 L/min.

Roughly calculate the required cutting fluid flow rate (L/min) equivalent to 2-3 times the hole diameter (mm). When the emulsion is used as the cutting fluid, the pressure can be appropriately reduced by 10-20%, and the flow rate can be appropriately increased.

5

The geometric parameters used in the cutting edge of the gun drill head

The grinding geometric parameters of the cutting edge of the gun drill head have an impact on the chip shape, dimensional tolerance, surface roughness, offset of the hole centerline, and tool life.

For difficult-to-machine materials that are prone to long chips, KBD can provide special cutting edge shapes and chip breakers.