A unique ladder structure, a drill can open a variety of specifications size aperture, a ladder drill on a box of drill bit.
Do not use the center red, compared with ordinary twist drill is not easy to break. Site construction, a ladder drill a variety of specifications apply.
Deburring, chamfering, open hole expansion, twist drill can not complete the function it becomes possible.
Compared with ordinary twist drill. Shaking small, without leading the use of the center can also open out the beautiful aperture out.
The use of tools: pistol drill, bench drill. While working while cooling water, can effectively extend the drill bit Life, recommended drilling speed 250 - 400 turn.