For drilling holes in metal special drill bits are used. They are the most common and effective tools for metalworking. Such drill bits are actively used both in industry and in household. Choosing them is not an easy matter because one or another operation requires certain drill bits which differ from each other by some characteristics.
As far as drill bits for metal are concerned, there are several most common types:
- Cylindrical spiral drill bits are the most popular and common ones. These tools are used mostly in household because they are suitable for drilling holes in many types of metal e.g. aluminum, steel, cast iron. As a rule it is made of high-speed steel (it is HSS or P6M5 steel grade mostly). Expensive drill bits are made of P18 steel characterized by high durability and excellent technical characteristics. Finding such drill bits is quite difficult nowadays.
- Conical drill bits are practically not used in households. They are intended for professional machines. The shank of this drill bit is made in the form of a cone.
- Core drill bits are intended for drilling large holes in any metal. They can also be used for concrete but a drill bit must have carbide soldering. These drill bits vary in diameter.
- Step drill bits are multipurpose tools for drilling large and small holes.
There are also drill bits from hard-alloy materials which are able to make a hole of any diameter even in the most durable metal. Such tools have a special design with one-sided and sharp surface.
How to choose a drill bit for metal
There is a large variety of drill bits nowadays and it is easy to face a problem of choosing the appropriate one. One chooses a drill bit depending on processed material. Drill bits for metal usually have a spiral shape; however, their shanks differ. For work with high-strength steel, carbon and alloy steel, instrument steel, drill bits with a cylindrical shank are used. This fact should be taken into account when choosing a tool. Such a drill bit can be used both in hand tools and stationary machines, although it happens less often. Drill bits with cylindrical shanks are the most common ones and are justly considered as universal.
It is necessary to choose a drill bit according to its diameter as well. A drill bit for metal with a cylindrical shank may have a diameter of up to 14 mm. Such a tool is capable of making large and even holes. You can find drill bits with a diameter of 20 mm but they are intended primarily for professional machines; besides it is quite difficult to find them. Their smallest diameter is 0.4 mm. Such a drill bit is able to make small and neat holes without deforming or damaging material.
Drill bits with a cylindrical shank may also be divided into three groups according to length of their working part:
A separate subgroup is left hand drill bits, which are designed specially for machines with left-handed rotation. Such drills are indispensable in cases where you need to drill out a broken bolt or fastener. For manufacturing of any drill bits high-speed steel is used. This material is able to withstand heavy loads and make neat even holes.
Manufacturing drill bits for metal with a cylindrical shank
The main method of manufacturing such drill bits is plunge-cut grinding from solid and finished billets. Their diameter may vary from 0.5 to 12 mm (accuracy class A1). The second method of manufacturing is using a polished profile when billets are obtained by the longitudinal screw rolled. All drill bits can be further processed in superheated steam. Wear-resistant coating can be applied too.