The classification of drills should start with their design. We are talking about the most important thing – the working part of the tool. So, according to the design of the working part, all drills are divided into the following types:
- Screw or spiral. The most common and demanded option. The diameter of twist drills can vary from 0.1 to 80 mm, and the length of the working part can reach 275 mm.
- Stepped. Convenient in that one drill can be used to create holes of different diameters. Used on sheet materials.
- Flat. Their cutting part of the plate is a spatula, a feather, therefore they are also called feather. Used to create large holes.
- Extra long twist drills are required wherever a sufficiently deep hole is required. They have screw channels for supplying liquid required for cooling during drilling.
- Centering. These drills are needed to create center holes in various parts..
- Hollow drills are also called core drills or ring drills. Only the annular narrow part of the material turns into chips.
- Drills for one-sided cutting. Such a tool is needed to create a hole with particularly accurate dimensions. The drill has a reference plane, both cutting edges are on the same side of the center axis.
This photo clearly shows almost all types of drills. They are subdivided according to their purpose, that is, the material with which they are intended to work:
- A – drill for metal;
- B – for wood;
- C – for concrete;
- D – flat, it is also a feather drill, also for wood;
- E – universal drill, can be used for both concrete and metal;
- F – for working with sheet metal;
- G is another universal drill, successfully used in plastics, wood, and metal.
Also, drills for working with glass and ceramics stand out separately, their tip is usually diamond-coated.
As for the difference between drills by the type of shanks, that is, the part that is attached to an electric tool or handle, they are:
- 1 and 2 in the scheme — cylindrical shanks;
- 3 – marked as SDS-plus;
- 4 – hex shank;
- 5 – shank with four edges;
- 6 – triangular shank;
- 7 – these drills are intended for screwdrivers.
The drills also differ in the shape of the hole, which can be created with their help:
If we talk not about the scope and types of construction, but about the features of the manufacture of the tool, then the drills are divided into the following types:
- Whole. These are always twist, twist drills. To create them, steel is used, which belongs to the high-speed type. These are brands P18, P9, P6M5, P9K15, P6M5K5. Carbide can also be used.
- Welded. The working part of such a twist drill is made of high-speed steel, but carbon steel is used for the shank.
- With carbide inserts. These drills are available with oblique, straight and helical flutes..
- Possessing replaceable carbide inserts or replaceable carbide heads. The first type is also called body drills..
It seems that the quality of the drill is difficult to determine. However, you don’t need to be a specialist to do this. Color can tell a lot about the quality of a tool..
If the drill is of an ordinary inconspicuous gray color, this will indicate its low quality. These tools are widespread, but they wear out rather quickly. The black color of the drill indicates that at the end of the manufacturing process it was treated with superheated steam. The quality of the black drill will be slightly higher than that of the gray.
A bit that has been tempered will have a slight gold tint. This is done to relieve internal stress. The brightly gilded drill bit was coated with titanium nitride. The highest quality drills, although their price will be noticeably higher than that of ordinary gray ones, but they will also serve the tool for a long time.
Drills differ in size. We have already written above about the minimum and maximum diameter drills can have. Of course, the diameter of the hole they create will also depend on the size of the tool..
Drills are usually purchased as a set. Indeed, you cannot say exactly when and what tool you need. Convenient suitcase-style kits do not take up much space and allow you to choose the right drill.
Craftsmen, who often use a variety of drills, usually create a convenient storage space themselves in the form of a stand on the desktop. So the tool is always at hand and will definitely not get lost in the workshop.
As you can see, the classification of drills is quite extensive, as are the types of work for which they are intended. Choose a high-quality tool, it can be universal, but experts advise you to still give preference to drills that are intended for a specific material.