3519 Twice Drilling Method to Reduce Exit Burr Formation
Details
Twice drilling method is proposed: In the stage of the prepared hole drilling, imperfect through hole which plastic deformation division is smaller than the finish diameter is opened. Then, the hole is finished by the drill with the point angle of burr depression effect. When the hole is finished with the drill of 50° point angle, the burr depression effect is remarkable. The height and thickness of the burr decreased in 1/10 and 1/2, respectively, compared with the drill of generally used 118° point angle.
