Choosing the best drill for metal: what is the difficulty, what criteria to rely on. Choosing the best metal drills How to choose a durable metal drill

Need for processing various products made of metal occurs not only among professionals, but also among many home craftsmen. When performing such processing, one cannot do without special tools, one of which is a metal drill. On the modern market, you can purchase already complete sets, including products of different diameters and lengths, or opt for a single copy that meets the required geometric parameters And mechanical characteristics. In both cases, the question arises of how to distinguish high-quality drills from low-quality ones and choose a tool that does not have to be changed after each processing cycle due to its breakage or critical dullness of the cutting part.

Drilling metal is a labor-intensive and complex process that requires a responsible approach to choosing cutting tool

Varieties and design features

Exist different kinds metal drills, differing from each other in design features and functionality. It is important that using drills designed for metal work, you can successfully drill holes in other materials, which include:

1. wood and wood-based materials;
2. different kinds polymer materials;
3. ceramics;
4. brick;
5. concrete.

The design of drills for metal work is specially developed to solve certain technological problems and taking into account the characteristics of the material for which they will be used. That is why experts advise those who do not know how to get an idea of ​​the design features of such a tool.

It is very important not to get confused in the variety of types of metal drills

Drills intended for metal processing consist of the following elements:

• the cutting part, which performs the main work of cutting metal;
• a shank with which the tool is fixed in the chuck of the equipment used;
• working surface responsible for removing chips from the processing zone.

Depending on your design drills for metal processing are divided into several categories:

1. flat;
2. spiral;
3. crowned;
4. conical

Flat

Drills, the working part of which has flat shape, also called feathers. Their most significant advantages are:

• insensitivity to distortions that any drill is subject to during processing with its help;
• simplicity of design;
• low price.

If we list the main disadvantages of tools of this type, then these should include:

• cannot be used for drilling holes large diameter;
• lack of automatic removal of chips from the processing zone (the design and geometry of such drills do not imply this option).

Spiral

Twist drills are the most common tool used to make holes in metal products. By its design, a twist drill is a cylindrical rod, on the side surface of which spiral grooves (one or two) are made, covering the entire working part of the tool. It is precisely such elements of a twist drill, such as helical grooves on its side surface, that ensure the removal of chips from the drilling zone.

Depending on the design and purpose, a twist drill can belong to one of the following categories.

• Cylindrical drills for metal work general purpose. The diameter of drills included in this broad category can reach up to 80 mm. They are actively used both in production and at home.
• Left hand twist drills with very limited applications. You cannot do without them in cases where it is necessary to drill a bolt with a broken head or a fastener from a threaded hole that cannot be unscrewed in any other way. There is a simple answer to the question of how to distinguish a drill of this type from a standard right-handed one: just look in which direction its spiral groove twists.
• High precision drills. They are chosen by those professionals or home craftsmen who are interested not in good, but excellent result upcoming processing. Tools of this type can be recognized by the designation A1. They allow you to create holes whose diameter is maintained to within a fraction of a millimeter.

Crowned

Drills of this type, made in the form of a metal cup with cutting teeth on the end working part, are used to create large-diameter holes in metal. The cutting teeth of such drills can be made of carbide or coated with diamond.

Conical

This category includes tools with smooth and stepped work surface. Used to make holes in metal products Not large thickness, they provide easy centering of the hole at the very beginning of drilling, which cannot be said about a tool with a cylindrical working surface. However, the main advantage of using stepped cone drills is that with the help of one such universal tool you can produce holes of different diameters.

Among metal drills, we should highlight tools that can be used to make holes even in high-strength materials.

Cobalt

These are tools created on a base doped with cobalt. Cobalt gives the drill high strength, as well as resistance to deformation under thermal and mechanical influence. Thanks to these characteristics, cobalt-type tools are successfully used for drilling holes in products made of high-strength and tough metals and alloys. Enough high price, which distinguishes cobalt drills, is fully justified by their characteristics.

Carbide

Carbide inserts are fixed on the cutting part of this type of drill. The main body of the tool is made of. For the production of plates, carbide alloys are used, which are characterized by exceptionally high hardness and wear resistance. By using such drills, the cutting plates of which are sharpened during the manufacturing process and are not subject to further regrinding, it is possible to successfully drill especially hard metals and alloys, as well as metal products of large thickness.

When choosing drills for metal, you must know exactly what technological tasks they will be used to solve, and also take into account the characteristics of the material in which you need to make a hole. To choose a tool that will meet your goals, you must also pay attention to the following parameters:

1. surface color;
2. quality of sharpening and symmetry structural elements;
3. working diameter;
4. shape matching typical parameters;
5. characteristics of the material of manufacture;
6. purpose and functionality;
7. manufacturer's reputation.

When deciding which drills to choose for metal processing, you should also take into account the characteristics of the equipment with which they will be used.

So, if you need to drill a large diameter hole in a metal product, for which powerful low-speed drills are used, you will need a tool that can be used in conjunction with them.

What does the color of the drill surface indicate?

The color of the surface of a metal drill is a parameter by which one can judge the quality of the presented tool. So, various colors metal drills mean the following.

Grey

This color has the surface of drills that are of the lowest quality and, accordingly, the lowest cost. Instruments with a surface of this color are not subject to any additional processing, which could increase their hardness, resistance to deformation and combustion. It should be borne in mind that when drilling hard metal, they may not be enough even for one hole.

Black

The surface of the drill acquires this color if it is treated with superheated steam. As a result of this treatment, the strength and wear resistance of the tool increase, and, as a result, the resource of its use increases. The cost of such products is slightly higher than gray ones, but is quite affordable for most consumers.

Light golden

This color means that the drill has undergone a tempering procedure after manufacturing. Such heat treatment allows not only to eliminate residual stresses in the internal structure of the tool, but also to improve its strength characteristics. Even in the photo, such a drill looks presentable and immediately inspires confidence in the quality of its workmanship.

Bright golden

This is the color of the best metal drills, the material of which contains titanium. Due to the content of this element in the steel from which the drills are made, when using them, the level of friction is reduced, which has a positive effect on the duration of their drills. efficient operation. Naturally, drills with a bright golden surface are quite expensive.

When choosing drills of a certain type, you should proceed from how often you will need to use them for metal work. It is also necessary to take into account the requirements for the accuracy and quality of the holes that need to be created in the metal product.

For frequent and intensive use in order to perform quality and precise holes It is better to choose more expensive, but also the highest quality bright golden drills.

Purchasing a cheaper tool will mean that you will have to change it quite often, and this will negate the initial savings. Choose more affordable ones drill types, the surface of which is painted black or light golden, is advisable in cases where it is necessary to perform one-time work related to drilling metal.

Classification by size

Modern manufacturers produce drills for metal work in a wide range of working sizes. To make it easier for the consumer to understand such diversity, the corresponding regulatory document (GOST) provides for the division of metal drills into Various types by size. Thus, the following categories of instruments are distinguished:

• short series, the length of which is in the range of 20–131 mm, and the diameter is 0.3–20 mm;
• elongated, the diameter of which, like the short ones, is in the range of 0.3–20 mm, and the length is 19–205 mm;
• long series, the length of which can be in the range of 56–254 mm, and the diameter – 1–20 mm.

The classification of drills depending on their length and diameter is regulated by the provisions of several regulatory documents– GOST 4010-77, 10902-77, 886-77.

How to understand the markings

Markings help you choose the right tool for drilling metal products. It's not difficult to figure it out. The marking of drills depending on their working diameter contains the following information about the presented tool.

• Miniature products, the diameter of which does not exceed 2 mm, are not marked at all.
• The markings of drills, the diameter of which is in the range of 2–3 mm, contain information about the grade of steel from which they are made, as well as the size of their cross-section.
• The marking of metal drills with a diameter of 3 mm or more contains the following data: working diameter, steel grade, and an imprint of the manufacturer’s logo.

By the alphanumeric designation of the grade of the manufacturing material, you can get an idea not only of the category of such an alloy, but also of the content of additional substances in its chemical composition.

Thus, the letter “P” in the marking of metal drills means that they are made of high speed steel. Steel alloys used in the manufacture of drills for metal work may contain additional substances that improve their performance characteristics. Such substances, in particular, can be molybdenum, which is designated by the letter “M,” and cobalt, designated in the labeling by the letter “K.”

Foreign manufacturers include more detailed information about the presented tool in the labeling. Having decided to purchase such drills, you will receive the following data from their markings:

• name of the country of origin;
• manufacturer's trademark;
• steel alloy grade;
• working diameter of the tool;
• accuracy class;
• short recommendations on materials that such a tool can drill.

Popular brands of instruments from foreign manufacturers

In order to know, when choosing foreign-made drills, which ones are better suited for solving certain technological problems, it is enough to have an idea of ​​the material that will be processed with their help. So, foreign manufacturers give the following recommendations for choosing a tool with a specific marking.

HSS-R and HSS-G

Using tools marked as follows, it is recommended to drill:

• steel parts manufactured by simple casting and injection molding; products made of carbon and, the strength of which does not exceed 900 N/mm 2;
• products made of metal alloys containing aluminum, graphite, copper, nickel, zinc (bronze, brass, cupronickel, etc.);
• blanks made of gray and malleable cast iron.

HSS-G Co 5

Drills with this marking can be used for processing metals whose strength reaches 1100 N/mm 2. Such metals, in particular, can be the following steels:

• carbon;
• stainless;
• thermally improved;
• acid-, heat- and heat-resistant;
• alloyed.

HSS-G TiAN/TiN

If such a designation is present on metal drills, this means that titanium-aluminum-nitride coating is applied to their working part. This coating significantly increases the resistance of drills not only to corrosion, but also to wear, which helps to increase their service life. Tools with this marking can also be used for processing metals and alloys with strength reaching up to 1100 N/mm 2. Manufacturers recommend using the following types of drills for processing:

• malleable and gray cast iron, in the structure of which graphite inclusions are spherical;
• copper-based alloys (brass, bronze, cupronickel);
• steel blanks produced by casting (including injection molding).

The best manufacturers

When choosing a tool for creating holes in metal, it is important not only to know what types of drills there are, but also to understand the brands presented on the domestic market. Both its durability and the results of the processing that will be performed with its help depend on who exactly made the drill.

• enterprises that produced drills in the territory of the former Soviet Union(their products, of which there are fewer on the market every year, are distinguished by high strength, reliability, wear resistance and, accordingly, durability);
• Ruko (drills produced under this brand can be manufactured with cross sharpening and various types of coating and are characterized by an excellent price-quality ratio);
• Bosch (the very brand under which such drills are produced already says a lot about their exceptionally high quality and reliability);
• Haisser (drills for this trademark due to the peculiarities of their design and the use of special alloys for their manufacture, they are able to successfully cope with their tasks even under extreme loads);
• “Bison” (under this domestic brand, affordable, but high-quality and reliable drills for metal work are produced).

How to sharpen

In order to efficiently sharpen a drill if its cutting part becomes dull, you must adhere to the following recommendations.

Drill set various holes In the hardest materials, a high-quality metal drill is capable of not becoming dull or breaking. High performance characteristics can be expected from a drill if it is correctly selected for the product being drilled and is made of quality material and sharpened as necessary.

Let us consider in detail the types of metal drills, their characteristics, features of use and criteria for choosing a cutting tool.

A metal drill is an indispensable tool for a modern builder

A metal drill is used for cutting holes in alloyed and unalloyed steel, its alloys, non-ferrous metals, cast iron and other types of metal. Often such drills are used when working with hard plastic materials. The scope of application of metal drills is limitless: the tool is used in the most different areas activities and in everyday life.

It is difficult for an ordinary buyer to navigate among the wide range of drills that are presented on the construction market today. Without competent consultation with a specialist, choose suitable model It's hard enough.

Structurally, a metal drill has a working part (cutting and calibrating part) and a shank.

Metal drills belong to the category of spiral drills, since they have spiral-shaped grooves along the entire length to remove chips

The place at the end of the drill is cutting part, where pointed edges are placed to allow the drill to penetrate the material. Behind the cutting part there is a calibrating part equipped with grooves for removing metal chips. The calibrating part is responsible for the smoothness of the edges of the hole and sets the desired diameter.

The material of manufacture and the structure of the working part determine the purpose of the cutting tool.

The drill is attached to a hand tool or machine through a shank, which can be conical, cylindrical or hexagonal.

Classification of drills for metal

Depending on the design features, metal drills can be divided into the following types:

Features of marking drills for metal

When choosing a drill for metal, you need to pay attention to its markings, which may indicate the diameter, steel grade, accuracy class and manufacturer.

Drills with a diameter of up to 2 mm are not marked; on products up to 3 mm, the diameter and grade of steel are indicated, and on drills of large sizes, more extensive information may be indicated.

Basic designations:

• marking starting with a letter R indicates high-speed steel products;
• numerical values ​​determine the content of a particular substance in the alloy, for example: K6- six parts of cobalt (increases the heat resistance of products); M4- molybdenum content;
• for comparison, a drill with markings R6M5K5 much stronger than a drill with markings R6M 5, due to the addition of cobalt (the price of reinforced cobalt drills is higher than conventional ones);
• imported analogues have designations H.S.S. or Din; an HSS drill for metal usually has additional markings of Latin letters indicating the working material ( HSS-G drill alloy and carbon steels, aluminum and copper alloys, cast iron; HSS-E in addition to the materials listed, they can cope with acid-resistant and stainless steel; HSS-G Tin- especially durable, suitable for drilling titanium alloy).

For drill manufacturing for metal, GOST regulates the use of tool high-speed steel grade P18

What can the color of a drill tell you?

The method of final processing of the drill will play out important role in ensuring the strength and reliability of the tool. The color of the drill indicates what materials were used to process the product.

Grey colour indicates that the drill could not be processed in any way. This is the cheapest and least stable product, which will not cope with all types of metal and will not last long.

Black color the drill acquires after treatment with superheated steam - this increases the service life of the product.

Dull golden hue- a sign of using tempering to relieve internal stress in hardened metal. This procedure reduces the fragility of the hardened drill, giving the material strength.

Rich golden color have drills coated with titanium nitrite - this ensures the highest wear resistance. These drills are the most convenient to use (reduced friction) and durable, the only drawback is their high cost.

Proper sharpening of a drill: the need for the process and the algorithm of actions

A high-quality drill is designed for long-term use, however, it can become dull over time. Of course, you can replace it with a new one, or you can avoid extra expenses, and sharpen the drill yourself.

In everyday life, for household needs, drills with a diameter of up to 16 mm are usually used, which can be sharpened on a regular sharpening wheel without resorting to “ high technology" If you don’t have a sharpener, you can use a grinder or electric drill, which must be secured before work.

Before you start sharpening a metal drill, you need to prepare:

• eyes must be protected with glasses, hands with gloves;
• prepare a small container for coolant (machine oil, water) - if the drill is not cooled periodically, the metal will overheat and will not be able to withstand high loads during drilling in the future.

The sequence of actions when sharpening a drill is as follows:

1. Pressing the drill firmly against grinding wheel, we process the back surface of the tool. The sharpening angle should not change.
2. After finishing processing the back surface, a regular cone should form (you can see it by looking at the tip of the drill from the side).
3. While maintaining the sharpening angle, the working part of the drill is processed.
4. Finishing of the rear part of the tool occurs after processing the working part of the drill.
5. The size of the bridge at the tip of the drill should not be more than 0.4 mm (for drill diameters up to 8 mm) and no more than 1-1.5 mm for larger drills.

You should not concentrate only on the tip; the entire working surface must be sharpened. side surface drill

When sharpening for the first time, it is advisable to practice on old, worn-out drills in order to feel how to hold and press the tool correctly. If you insert a “test piece” into a drill and drill a couple of holes, it will immediately become clear where the error was made during processing.

When choosing drills for working with metal, you should adhere to the following recommendations:

With the right choice of tool and good sharpening, metal drills can be used for a long time and without problems, both for their intended purpose and for drilling holes in other materials: wood, plastic, plexiglass and stone.

Metalworking does not cause difficulties only for those who know how and what to work with. Beginners in this business have to start with the basics, for example, finding out which metal drills are better or what shape of tip is needed for round holes.

There are not many special tools that can be used to work without the help of a machine. Therefore, it is important to understand what drills are, how they are classified and what they are intended for.

Metal drills: design differences and markings

The modern market offers big choice cutting tools for metal processing. You can purchase a ready-made universal kit or a set of metal drills.

For a one-time use, you should not pay for everything at once, but choose something specific for performing any operation that meets certain characteristics.

Tip: When looking at a tool, pay attention to the markings, where many parameters are coded. These are letters and numbers that all types of metal drills have.

From a short inscription, an experienced master immediately understands all the parameters:

• metal fabrication;
• what material to work on;
• drill working diameter;
• accuracy class;
• country of origin (logo).

Spiral gimlets minimum diameter are not marked. But the rest of the designations cannot be understood by a beginner. House master. For example, the marking P6M5K5 indicates a composition with a certain percentage of tungsten, molybdenum and cobalt - this is the highest quality drill.

But also with 15% cobalt quality tool, in the designation P9K15 indicates that this is a high-speed steel drill.

Imported alloy steel products are marked with HSS:

• HSS-E VAP (for working with stainless steel);
• HSS-E with the addition of cobalt (for working on metals with high viscosity);
• HSS-Tin with titanium (for increased cutter hardness);
• HSS-4241 drills aluminum products;
• HSS-R tool for maximum durability.

Attention: Look for the markings on the shank of the metal drill, as shown in the photo.

Which brand of drill is better?

To this day, home craftsmen have preserved tools and equipment from Soviet times. This is not to say that these were bad drills, especially Pobedit ones, but how to sharpen a drill for metal without equipment?

It’s easier to buy a new cutting tool from foreign and domestic manufacturers:

• Bosch – any product of exceptional quality.
• Ruko – Look for the best Phillips carbide drill bits for reliability.
• Haisser - their drills with titanium-nitride coating can withstand extreme loads (processing steel, copper, bronze, cermets, etc.).
• “Zubr is a well-established domestic brand, the optimal price-quality ratio, offering reliable cutters for metal, in particular with cobalt.

Important: Any drill will take a hole in a thin product made of a malleable alloy. For “specialists” working in metal, it is not profitable to buy cheap gimlets of dubious quality and spend time sharpening them.

As a rule, drills are specialized for metal and wood, but they can also work with other materials, including concrete, ceramics and polymers.

Drills, their types and characteristics

Drills that structurally have much in common are used for metalworking:

• cutter;
• working surface (provides advancement while removing chips);
• shank (fixed in the chuck).

Main classification:

• step or cone (conical) drills;
• feather (flat);
• crowned;
• spiral.

You can find other types of metal drills in catalogs, but these are only discrepancies in the names. For example, annular cutters are the same core drills. On the end part you can see diamond-coated teeth. Standard core drills select the contour of the hole.

Step or conical drills – for holes required diameter in thin metal plates. The advantage is that there are several diameters in one tip, but they are practically not used in everyday life.

Classification by material

Cutting tools are most often made of steel, but when metalworking with hard alloys, the temperature rises. If the temperature threshold is violated, the drill becomes dull - you need cutters with plates of sufficient hardness, for example, alloyed with cobalt.

Titanium drills – good alternative cobalt for hardness and reliability. Technological use provides a guarantee long work with factory sharpening.

Carbide carbide tools demonstrate increased wear resistance. Although these drills do not require regrinding, this tool is used by professionals when working with thick metal. For these purposes they are used powerful drills operating at low speeds - drills are included.

From intensive use the tool loses its properties, but this does not apply to drills of a bright golden hue.

By the way, by the color of the drill you can judge its performance characteristics:

• Black surfaces - from hot steam to increase wear resistance to extend the life of use.
• Gray – drills for household use, after working with hard metal they become unusable.
• Golden – high speed drills who passed special procedure hardened, they inspire confidence even in experienced craftsmen.
• Bright gold surfaces are the best titanium metalworking tools, but they are quite expensive.

The dimensions of metal drills do not affect quality, but a wide range of drills makes it possible to choose the right tool for any metal work. The size scale is regulated by GOST standards. The working length of the cutters ranges from 20 mm to 131 mm, and their diameter ranges from 0.3 mm to 20 mm.

Photo of metal drills

The Hand Tools company offers to buy metal drills from RESOLUX. Products manufactured under this brand are designed for comfortable work and making the most accurate holes in metal.

Depending on the standard, materials, characteristics, cost and production method, there are different types of tools.

According to GOST 10902-77, in terms of quality and price, medium series drills with a cylindrical shank RESOLUX are divided into three groups:

1. Rolled drills R6M5 with the following characteristics:

• working part - polished;
• accuracy class B1;
• 1 - 20 mm;

Drills are mounted in three-jaw chucks of machine tools or hand drills. Manufactured in sizes starting from 13 mm. In this case, the shank is ground down to 13 mm, due to which a drill with a diameter of 16 mm can be fixed in a 13 mm chuck.

2. Drills for stainless steel P9 with the following characteristics:

• working part - polished;
• accuracy class B1;
• 1 - 13 mm.

Tools allow you to maximum efficiency process stainless steel, structural and other difficult-to-process steel grades. They are located in the middle price segment.

3. Drills R6M5 with accuracy class A1

This professional tools, widely in demand for production needs, at enterprises where increased demands are placed on the properties and characteristics of products, as well as on the precision of drilling.
In the production of tools in this series, high-quality steel grade R6M5 and the grinding method are used.
Suggested sizes: 1 - 13 mm.

Rolled drills are the most attractive in price, as they are made in the simplest and most accessible method. The low cost of the rolling method is explained by the high speed and automation of production:

• at the first stage, special blanks are made from rods;

• then they are heated and pulled through, due to which the working part, similar to a spiral, is formed;

• the workpieces are carefully ground and sharpened.

Grinding a working spiral from a solid workpiece is the most expensive production method. The reasons for this: low production speeds, the most careful processing and, as a consequence, highest quality products.

Drills with a conical shank are produced by milling. Since complete automation of the process is impossible due to big size blanks, it requires a lot of time.

You can buy long and elongated drills with a conical or cylindrical shank from the company " Hand tool" in Moscow. For more information about prices for metal drills, please call.

Choosing a tool for apartment renovation. Choosing the right drills.

Drill – universal tool, which is simply indispensable when carrying out repairs of all kinds of complexity. Today there are many types of drills, and therefore it is very important not to make a mistake and make the right choice, so that later you do not have to replace, or even simply throw away such a tool if it fails prematurely. The site will tell you how to make the right choice.

Essentially all drills differ only in their appearance (diameter and length), as well as the material for which they are designed to work and, as a result, sharpened. Accordingly, it is necessary to initially select the size of the drill (it is necessary that such a tool matches the thickness of the material that will be drilled, or self-tapping screws, anchors, etc.). Next, you should select drills depending on the work that will be carried out.

Selecting a drill for metal

Metal drills differ from conventional drills (meaning those used for wood processing) in their versatility. Such a tool is indispensable when working with metals and can be used to create holes in alloyed and unalloyed steels, cermets, cast iron and non-ferrous metals.

The most common today are twist drills for metal. As a rule, such metal drills are a cylindrical rod in which two helical grooves are made, forming cutting edges. These grooves are made at an angle of 10-45° to the axis of the cutting tool.

You should also pay attention to the material from which the drill is made. Today, the highest quality tools for metal processing are made from high-speed steel (for example, R6M5) or alloy steel (9ХС). Such drills have increased durability and strength, and also make it possible to achieve maximum results in progress.

Choosing a drill for concrete

Concrete is a strong and powerful material, which is very difficult to process, especially to drill a hole. As a rule, special drills tipped with tungsten and cobalt hard alloy (“win”) are used for drilling concrete. Moreover, thanks to the use modern technologies In the manufacture of cutting tools, drills made from modified tungsten-cobalt alloys have appeared on the market.

For processing brick or concrete, drills with soft or medium soft tips are used. In the same case, if you need to process granite or other hard materials (for example, the same tile), then you simply cannot do without the use of Pobedit drills with plates of medium and high hardness (in addition, a series of teeth and reverse sharpening are performed on them).

Wood drill bits: how to choose?

For wood processing modern market offers widest choice highly specialized cutting tool. In particular, it is simply impossible to imagine working with wood without the use of three main types of drills:

• Twist drills are a sharply sharpened metal spiral that is used to create holes in wood of small diameter (8-28 mm) but quite significant depth (300-600 mm). Thanks to its spiral shape, such a tool is very easy to remove from working area after completion of work.
• Feather drills, as a rule, are used in cases where it is necessary to create any blind hole in wood with a diameter of 10 mm or more. It should be noted that such a drill can only be used to create holes, since due to the absence of cutting edges on the side surface, it is simply impossible to drill out what is already there.
• Cylindrical (ring, core) drills are widely used to create large diameter holes (from 26 mm). The main advantage of using such drills is the ability to obtain a neat hole without scoring or other defects, as well as high processing efficiency.

When choosing drills for work, you need to pay attention to their appearance. If we are talking about a truly high-quality tool, it should not have chips, dents, scratches or other defects. Cutting edges must be sharpened with high quality along the entire length and have a uniform color.

When choosing drills, regardless of the material for which they are intended for processing, you need to pay attention to their color - it is easy to determine from it the finishing hardening treatment that was carried out:

1. Steel gray – no treatment carried out.
2. Black – the drill has been treated with superheated steam to harden it.
3. Golden – the drill has undergone tempering treatment to relieve internal stresses in the metal.
4. Bright gold – a layer of titanium nitride is applied to the surface of the instrument, designed to strengthen it and extend its service life.

It would not be amiss to note the fact that when choosing a drill, you also need to pay attention to the manufacturer. It is best to give preference to famous companies that have been on the market for more than one year. Only in this case can you avoid counterfeits and unnecessary waste of money.

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