What Is a Step Drill?
A step drill (bamboo shoot drill) is a drill used to drill holes of different sizes in metals and other materials.
While general drills are straight and the hole diameter is uniform, the conical shape allows the hole diameter to be varied as desired.
:Because of its unique shape, it is also called a bamboo shoot drill.
It is often used in conjunction with electric drills, etc., and can easily perform drilling and deburring.
With a step drill having a spiral-shaped cutting groove, chips are discharged outward so that holes can be drilled without clogging the inside of the drill.
Uses of Step Drills
Step drills are suitable for drilling holes in plastic materials and metals such as aluminum, stainless steel, and brass.
On the other hand, they are not recommended for soft materials such as wood and carbon-based materials, as the high frictional heat can cause scorching.
When a hole is drilled, the edge of the hole is usually sharp, so it is deburred to round off the corners.
In this case, the step drills can easily deburr the hole by pressing one of the outer steps.
Principle of Step Drills
Step drills are equipped with several drill blades of different diameters, each of which has a specific diameter.
The number of steps and diameters vary by manufacturer, but typical examples are:
- 9 steps (4, 5, 6, 7, 8, 9, 10, 11, 12mmφ)
- 10 steps (4, 6, 8, 10, 12, 14, 16, 18, 20, 22)
- 15 steps (4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 33)
and other step drills are available.
Many of them have titanium-coated surfaces for excellent sharpness and durability.
As with regular drills, the durability of the drill itself is further improved by the use of cutting oil, which reduces metal-to-metal friction.
However, because of its stepped structure, it cannot drill holes in thick materials and is limited to a thickness of a few mm at most. Step drills are suitable for drilling thin materials.
There are two types of step drills: spiral and straight. The spiral type allows efficient drilling due to its good chip evacuation.
Many of them have a thinning process at the tip, which allows the drill to bite into the material without a punch.