Drilling is one of the types of machining of material by cutting. This method uses a special cutting tool - a drill. With it, you can make a hole of different diameters, as well as depths. In addition, it is possible to create multi-faceted holes with different cross sections.
Purpose of operation
Drilling is a necessary operation if you want to get a hole in a metal product. Most often, there are several reasons for drilling:
- you need to create a hole for threading, reaming, reaming or boring;
- it is necessary to place electric cables, fasteners in the holes, thread anchor bolts through them, etc .;
- separation of blanks;
- weaken collapsing structures;
- depending on the diameter of the hole, it can even be used to lay explosives, for example, in the extraction of natural stone.
This list can be continued for a long time, but it can already be concluded that the drilling operation is one of the simplest and at the same time quite necessary and common things.
Expendable materials
Naturally, for the implementation of the drilling process, you must have a drill. Depending on this consumable, the diameter of the hole will change, as well as the number of its faces. They can be of circular cross section, or they can be multifaceted - triangular, square, pentahedral, hexahedral, etc.
In addition, drilling is an operation in which the drill will heat up to high temperatures. For this reason, it is necessary to accurately select the quality of this element, based on the requirements of the material with which it is necessary to work.
- A fairly common material for the manufacture of drilling tools is carbon steel. Elements of this group are marked as follows: U8, U9, U10, etc. The main purpose of such consumables is to drill holes in wood, plastic, soft metals.
- Next are drills made of low alloy steel. They are intended for drilling the same materials as carbon ones, but their difference lies in the fact that this brand of elements has an increased value of heat resistance to 250 degrees Celsius, as well as an increased drilling speed.
Improved Drills
There are several types of drills that are designed for better materials:
- The first type of drill is made of high speed steel. The heat resistance of these consumables is much higher - 650 degrees Celsius, and they are designed to drill any structural materials in an unhardened state.
- The next group is carbide drills. They are used to make holes in any structural non-hardened steels, as well as in non-ferrous metal. A feature is that drilling at higher speeds is used. For the same reason, the heat resistance is increased to 950 degrees Celsius.
- One of the most resistant elements is drill with borazon. They are used for work with cast iron, steels, glass, ceramics, non-ferrous metals.
- The last group is diamond drills. They are used for drilling the hardest materials, glass, and ceramics.
Types of Drilling Machines
For drilling operations, the following types of drilling machines can be used:
- Vertical and horizontal drilling devices. Drilling holes for such machines is a basic operation.
- Vertical and horizontal boring machines are used. Drilling is considered ancillary operations for these devices.
- Vertical, horizontal and universal milling machines. For these units, drilling is also a secondary operation.
- Lathes and turning-backing machines. On the first type of device, the drill is a fixed part, and the workpiece itself rotates. For the second type of device, drilling is not the main operation, but the drill is a fixed element, as in the first case.
These are all types of drilling machines on which you can carry out all the required operations.
Hand tools and auxiliary operations
In order to facilitate the drilling process, several auxiliary operations are used. These include the following:
- Cooling. When drilling, a variety of cutting fluids are used. These include, for example, water, emulsions, oleic acid. Gaseous substances, for example carbon dioxide, can also be used.
- Ultrasound. The ultrasonic vibrations that the drill produces are used to increase the productivity of the process, as well as to enhance chip crushing.
- Heating. In order to improve the drilling of a metal having a high density, it is preheated.
- Hit. To work with certain surfaces, such as concrete, it is necessary to use rotary movements to increase productivity.
This procedure can be carried out not only on machines in automatic mode, but also on manual equipment. Manual drilling involves the use of tools such as:
- Mechanical drill. For drilling, the mechanical strength of a person is used.
- Electric drill. It can carry out conventional and rotary hammer drilling. It works from an electric network.
Types of procedure and cooling
There are several main types of drilling - this is the equipment of cylindrical holes, polyhedral or oval, as well as the drilling of existing cylindrical holes to increase their diameter.
The main problem that arises in the process of drilling metal is the strong heating of the consumable element, that is, the drill, as well as the place of work. The temperature of the material can reach 100 degrees Celsius or more. If it reaches certain values, then the occurrence of burning or melting is possible. It is important to note here that many steels that are used for the production of drills lose their hardness when heated, due to which friction will only increase, so the element, unfortunately, will wear out faster.
In order to combat this drawback, various cooling agents are used. Most often, with vertical drilling on the machine, it is possible to organize the supply of coolant directly to the place of work. If it is carried out using hand-held devices, then after a certain period of time it is necessary to interrupt the process and dip the drill into the liquid.
The essence of drilling
Hole drilling technology is the process of forming grooves by removing chips in a solid material using a cutting tool. This element performs rotational and translational or rotational-translational movements simultaneously, which forms a hole.
The use of this type of material processing is used to:
- to receive non-conforming holes with a low degree of accuracy and a roughness class used for fixing bolts, rivets, etc.
- get holes for threading, deployment, etc.
Processing options
Using the procedure of deep drilling or reaming, it is possible to obtain holes that will be characterized by the 10th or 11th degree of quality of surface roughness. If it is necessary to obtain a better hole, then after completion of the processing process, it is necessary to additionally drill and drill it.
In order to increase the accuracy, in some cases, you can resort to careful adjustment of the position of the machine, properly sharpened consumable element. A method is also used in which work is carried out through a special device that increases accuracy. This device is called a jig. There is also a division of the drill into several classes. There are spiral with straight grooves, feather, used for deep or ring drilling, as well as centering drills.
Drill Design Description
Most often, a conventional twist drill is used for work . Specials are used much less frequently.
The spiral element is a two-toothed cutting part, which includes only two main parts - this is the shank and the working part.
If we talk about the working part, then it can be divided into cylindrical and calibrating. On the first part of the drill are two helical grooves opposite each other. The main purpose of this part is the removal of chips, which is released during operation. It is important to note here that the grooves have the correct profile, which ensures the correct formation of the cutting edges of the drill. In addition, the necessary space is created, which is necessary for the removal of chips from the hole.
Drilling technology
It is important to know a few specific rules. It is very important that the shape of the grooves, as well as the angle of inclination between the direction of the axis of the drill and the tangent to the tape, be such as to ensure easy chip removal, while not loosening the tooth section. However, it is worth noting here that this technology, and especially numerical values, will noticeably change depending on the diameter of the drill. The thing is that an increase in the angle of inclination leads to a weakening of the action of the drill. This disadvantage manifests itself the stronger, the smaller the diameter of the element. For this reason, you have to adjust the angle under the drill. The smaller the drill, the smaller the angle, and vice versa. The total angle of inclination of the grooves is from 18 to 45 degrees. If we are talking about drilling steel, then it is necessary to use drills with an angle of inclination from 18 to 30 degrees. If the holes are made in brittle materials, such as brass or bronze, then the angle is reduced to 22-25 degrees.
Principles of work
It is important to start with the fact that, depending on the material of the tool, the cutting speed will also change . For example:
- If drilling is carried out using tool steel elements, the minimum speed is 25 m / min and the maximum speed is 35 m / min.
- If machining is carried out by drills belonging to the category of high-speed, then the minimum speed is 12 m / min and the maximum is 18 m / min.
- If drills of their carbide materials are used, then the values are 50 m / min and 70 m / min.
It is important to note here that the drilling technology involves the choice of the speed of the procedure depending on the diameter of the element itself and low feed rate (the speed also increases with increasing diameter).
A characteristic feature of the work is the use of a standard vertex angle for the drill, which is 118 degrees. If you need to work with raw materials, which are characterized by high hardness of the alloy, then the angle must be increased to 135 degrees.
Drill safety
One of the important tasks during this type of machining was that it was necessary to preserve the cutting properties of the consumable. The safety of these parameters directly depends on which method of operation was chosen and whether it was suitable for this material. For example, in order to eliminate the breakage of the drill in the aisle, it is necessary to greatly reduce the feed at the time of withdrawal of the drill from the hole.
Particular attention should be paid to drilling technology in situations where the depth of the hole exceeds the length of the helical groove of the consumable. At the moment the drill is inserted, the chips will still form, but during the exit it will no longer be. Because of this, the drill breaks very often. If there is no way out of the situation, then you need to periodically remove the drill and manually clean it from unnecessary elements, that is, chips.
Drill bits
In order to make a hole in a certain coating, it is necessary to use crowns. However, they also need to be selected correctly, based on certain parameters. Currently, there are three main types of material used to create crowns - this is diamond, win and tungsten carbide. A feature of the diamond core is that it performs hammerless drilling. In this case, a more correct hole geometry is obtained.
The main advantages of diamond nozzles were the following: the ability to cut reinforced concrete materials, low noise and dust, the absence of structural damage, as the technology does not use impact force.