The Experimental Study On Chisel Edge Grinding For Improved Deep Hole Twist Drill

Chisel edge of twist drill has direct influence on the cutting performance.The main grinding types of chisel edge includes,No chisel edge grinding,Cross grinding,Cup type grinding,H type grinding,SE drill point and Multifacet dills.Cross grinding is the most effective method,the chisel edgeground in cross type is relatively short.Cross grinding will generate the inner edgewhich can overcome the fault of large negative rake angle at the core of twist drill.The mathematical model of cross grinding chisel edge is very important,But the literatures on the mathematical model of cross grinding chisel edge is not comprehensive.This paper establishes the mathematical model of cross grinding chisel edge in vector and five sharpening parameters,????? x?? y and ?,are defined for grinding the chisel edge.The paper analyzes the relationship between grinding parameters and structural parameters of chisel edge.This paper uses the method of experimental research and carries out experiment of cutting performance for carbide deep hole twist drill with ? 8,ratio of length to diameter is 1:15,by changing respectively the radius of inner edge,rake angle of inner edge,eccentricity,distance over the center and chip groove angle.The experimental results show that the axial force reduced by 5% with the increase of radius of inner edge as the radius of inner edge is in the range of 0.5 ~ 2 mm,that the ratio of the radius of the drill is between 10%~50%,The axial force reduced by 16% with the increase of rake angle of inner edge as the rake angle of inner edge is in the range of-5 degrees ~ 5 degrees,The axial force increased by 3% with the increase of eccentricity as the eccentricity is in the range of 0.5 ~ 2 mm,the ratio of the radius of the drill is between 2%~10%,the axial force reduced by 12% with the increase of distance over the center as the distance over the center is in the range of 0.5 ~ 2 mm,the ratio of the radius of the drill is between 1%~10%,The best value of chip groove angle at 50 degrees ~70 degrees,the ratio of point angle in the range of 35%~50%,is 60 degrees.Which suggests that the reasonable choice of structure parameters can effectively improve the cutting performance of the drill.This paper only carries out the experiment on carbide deep hole twist drill that ? 8,ratio of length to diameter is 1:15.As the drill material is more,Such as high speed steel of the application of a wide range,Further experimental studies on drill of other materials and different length to diameter ratio should be carried out.In addition,this paper only makes a relative experiment on the axial force and the durability of the drill,The cutting temperature,the size accuracy of the hole and the surface roughness of the hole have not been done.After that,we will continue to carry out further experimental research on this subject.