Tool Effect on Surface Roughness

(1) Tool geometric parameters

Among the geometric parameters of the tool that have a greater impact on the surface roughness are the main declination angle Kr, 

the secondary declination angle Kr and the radius re of the tool nose arc. When the main and minor deflection angles are small, 

the height of the residual area of the processed surface is also small, so the surface roughness can be reduced; the smaller the minor 

deflection angle, the lower the surface roughness, but reducing the minor deflection angle is likely to cause vibration, so reduce The 

secondary deflection angle should be determined according to the rigidity of the machine tool. The influence of the radius re of the 

tool nose on the surface roughness: when the stiffness is allowed, the surface roughness will decrease when the re increases, and 

increasing re is a good way to reduce the surface roughness. Therefore, reducing the main declination angle Kr, the secondary 

declination angle Kr and increasing the radius r of the tool nose arc can reduce the height of the residual area, thereby reducing the 

surface roughness.

"For the selection of the arc angle of the tool tip, it is recommended to choose according to the rigidity and roughness requirements of the workpiece. If the rigidity is good, try to choose a large arc angle, which can not only improve the processing efficiency, but also improve the surface finish; but when boring Or when cutting slender shafts or thin-walled parts, because of the poor rigidity of the system, a smaller tool nose arc radius is often used,” said the tool engineer when making tool selection plans. For the specific tool nose arc angle and roughness value, please refer to the following text (relationship among tool feed, tool nose arc angle, and machined surface roughness).

(2) Tool material

When the tool material has a high affinity with the metal molecules of the processed material, the processed material is easy to bond 

with the tool to form built-up edge and scales. Therefore, if the bonding is serious and the friction is serious, the surface roughness 

will be large, and vice versa. . When processing the same workpiece, different tool materials can obtain different surface roughness. 

For example, when processing cast iron, it is difficult for cemented carbide inserts to reach the roughness of Ra1. Excellent stability 

and wear resistance, so the roughness of cast iron can reach Ra0.8-Ra1.6.

(3) Tool wear

Tool wear is divided into three stages: initial wear, normal wear and severe wear. Because there will be some burrs, irregular asperities, microcracks, etc. on the surface of the tool, the wear is relatively severe in the initial stage of cutting, resulting in a large change in 

surface roughness; after entering normal wear, the cutting process is relatively stable, so The change range of the surface roughness 

decreases; with the increase of the wear amount, the tool enters the severe wear stage, the wear rate of the tool flank rises sharply, 

the system tends to be unstable, and the vibration increases accordingly, and the change range of the surface roughness also rose 

sharply.

There are three points of impact of diamond tools on surface roughness, tool geometry parameters, tool material and tool wear.