5. Transverse edge angle
The cross blade is a cutting edge perpendicular to the axis of twist drill bit. The angle of the cutting edge includes the oblique angle of the transverse blade, the front edge of the transverse blade and the back angle of the transverse blade.
(1) The oblique angle of the transverse blade is in the end plane, between the cross edge and the main cutting edge. It is formed naturally when grinding the drill bit, standard twist drill bit with normal grinding angles and corners. The larger the rear angle, the smaller the angle. Decreasing the angle will increase the length of the transverse edge.
(2) The rake angle of the transverse edge is negative because the base surface of the transverse edge is located in the tool body.
(3) Rear angle of transverse edge.
For standard twist drill bit, = – (54 degree ~60 degrees), =30 degree ~36 degrees. Therefore, during drilling, the metal extrusion and scraping deformation at the transverse edge is serious, and the axial force is very large. Experiments show that about 50% of the axial force is produced by a transverse blade when machining with standard twist drill bit. For larger diameter twist drill bit, the cross cutting edge is usually needed to reduce the axial force.
(Please refer to passage Relationship between Geometric Angle and Precision of Twist Drill Bit Ⅰ and Relationship between Relationship between Geometric Angle and Precision of Twist Drill Bit Ⅱ to read the following content.)
Post time: Mar-13-2022