Drill into a lot of categories, but no matter what kind of drill, has meet the eligibility criteria, and now with the drill bit applications more widely, drill manufacturers sell more and more, then you know what? A qualified drill, you should have what conditions? Here you introduced one by one!

① angle of 118 ° ± 2o 2
After the angle α0 ② hole at the edge of 10 ° -14 °
③ chisel edge angle is 50 ° -55 °
④ two corners and two main cutting edge length and composition of the drill axis should be equal
⑤ two main flank to grinding smooth.

Optional step drills, straight flute drill or drill deep hole drilling, etc., the Society of the above characteristics Oh look!