Types of drills, drill bits, and how to choose them

Drills are power tools that can perform a wide variety of drilling and screw-tightening operations on a wide range of materials, such as wood, metal, and plastic, etc.  As there is such a wide variety of specialized drill bit variations, we recommend choosing the product that meets your specific needs.

Types and features of drills and drill bits

Drills are available in a wide range of products, from small, motorized ones that are easy to maneuver to powerful ones that can easily perform heavy-duty work. An important point in determining the nature of a drill is the bit portion that actually applies force to the material. Let's take a look at the specialized bits used mainly in common electric drills, such as driver drills and impact driver drills.

How to choose the drill bit based on their purpose/function

Solid Drill

This is a bit with a basic structure in which the entire drill is made of a single material.

ソリッドドリル

Top solid drill

Only the tip of the bit is made of a different type of material.

先ムクドリル

Tipped drill

A bit with a tip made of a different material, such as a superalloy, brazed to the cutting edge of the drill. Of these, those that use a throw-away tip are called throw-away drills.

付刃ドリル

Purpose

Core drill

Used for pre-drilling and finishing of pre-drilled holes, three or four groove drills are common and are characterized by the absence of a cutting edge in the center of the drill.

コアドリル

Pivot drill

The diameter of the drill portion is narrower and different from that of the shank portion. It is mainly used for shallow hole drilling.

ルーマ型ドリル

Step drill

This drill has multiple diameters and is suitable for drilling stepped holes. It can also be used for chamfered hole drilling.

段付きドリル

Starting drill

This drill is used for positioning holes before drilling. It can also be used for chamfering after machining.

スターティングドリル

Center drill

This drill is shaped for drilling center holes. Mounted on a lathe or grinder, it is used for drilling center holes.

センタ穴ドリル

Special shape of the body

Depending on the purpose and anticipated use, some products are designed with a special shape for the body of the drill. Common types include those with oil holes in the body, double-groove drills designed to have multiple diameter leading edges, flat-groove drills designed with narrow land widths, and double margin drills with two margins instead of one.

Torsion structure

There are two types of drills: right-twist drills, in which the drill grooves are twisted to the right rotation, and left-twist drills, in which the grooves are twisted to the left rotation. Make sure to select the one that matches the direction of rotation of the drill body. Straight-twist drills, in which the grooves are not twisted at all, are mainly used for nonferrous materials.

Body length

There is no clear standard for length, but they can be classified into three types in order of shortest to longest: stub, regular, and long. Regular drills, which are medium in both body length and groove depth, are the most versatile drills.

How to choose a drill

There are a wide variety of drills available in the market today.  The following basic points can be a good starting point to select a good drill

Target material

Drills are made of a variety of materials, such as wood, metal, plastic, and concrete, etc. Drills designed for hard materials such as metal can be used for softer materials such as wood, but the finish will be rough. If you want a beautiful finish, select a drill that is suitable for the target material.

Length

Drill length is important when drilling through thick materials. The longer the drill blade, the more holes can be drilled in thicker materials.

Shank shape

There are two main types of chuck part shapes for drill bodies: keyless chucks and hexagonal shaft chucks. The keyless chuck can accept two types of shanks, round or hexagonal, while the hexagonal shaft chuck can only install a hexagonal shank.

There are several types of shanks, such as cylindrical straight shanks, straight shanks with tangs, and taper shank drills (Morse taper shank drills), etc. When selecting a bit, make sure to check whether the shank of the bit can be attached to the drill body you have.

Summary

Drills are reliable tools that are widely used in various industries. It is important to understand the features of each drill available, select the one that best suits your purpose, and use it accordingly.