What are metal drills made of, and what does the manufacturer’s marking mean?

Metal drills

For drilling metals, screw or, as they are more often called, twist drills are used. Although almost identical in design, these tools may differ in material, type of additional processing, and sharpening features. There are many varieties of drill bits optimized for different metals, drilling depths and other working conditions.

What are drills made of?

High-speed steel is used to make metal drills. This is a group of highly alloyed alloys, which, in addition to iron and carbon, include tungsten, molybdenum, cobalt, vanadium and other elements.

High-speed steel differs from ordinary tool steel in that a drill made from it remains operational when heated. Tool steel at normal temperatures is not inferior in hardness to high-speed steel, but when heated above 200 o C, tempering occurs and it becomes soft. High-speed steel retains hardness up to 500-600 o C, and some grades – up to 1000 o C.

Tungsten is the main component that increases the “red resistance of steel” (the ability to maintain hardness when heated). However, due to limited reserves of tungsten, it was necessary to abandon steel with a high tungsten content and switch to molybdenum alloys. When the tungsten content is within 6%, the required qualities of drills are ensured by the addition of molybdenum, cobalt and other elements. Tools made from P18 steel are no longer produced, and even P9 is rare.

In foreign classifications, high-speed alloys are designated by the abbreviation HSS (High Speed ​​Steel). There are several varieties of them, and some of them are similar to the alloys specified in GOST. High-speed steel grades are designated by the letter “M” followed by a number. Let's compare several of the most commonly used brands.

Steel with low tungsten content and high molybdenum content (1.5 and 8%, respectively). It is not highly durable and is used for the manufacture of general purpose drills.

The alloy contains 6% tungsten and 5% molybdenum, which gives drills made from it high hardness. The Russian analogue is R6M5. Drills made from this steel have good wear resistance and red resistance.

Drills made of this steel are used for deep drilling and high-force work. Its composition has a reduced tungsten content (1.75%), but an increased amount of molybdenum (8.75%) and vanadium (2%). The Russian analogue is R2M9.

The Russian analogue of this alloy is R6M5K5. This steel differs from M2 (R6M5) in its higher “red resistance” due to the addition of 5% cobalt. The alloy also contains silicon, magnesium and nickel. Drills made of M35 steel can withstand high heat and provide high performance.

This alloy contains a little tungsten, but a high content of molybdenum and cobalt. Drills made from it have high red resistance and hold an edge well. Work well at high cutting speeds and on tough materials. The Russian analogue is R2M10K8 steel.

Features of drills and their markings

The foreign marking system for drills reflects some of the features of their manufacture and the most important components of steel.

Unground drills are produced by helical rolling. They use relatively soft, deformable steel. After rolling, the tool is hardened. The letter “R” may be missing from the marking.

Ground drills are made by grinding CBN (cubic boron nitride). This is the most common type of tool for a wide range of tasks. The drills have high wear resistance and minimal radial runout.

HSS-PM

Drills made using powder metallurgy technology. Used for processing hard metals.

HSS-E (HSS-Co)

Cobalt drills made from alloys with a high cobalt content. A number may be added to the marking indicating the percentage of cobalt rounded to the nearest whole number. For example, HSS-Co5 or HSS-Co8, which corresponds to M35 or M42 alloys.

HSS-TiN or HSS-TiAN

Titanium drills are coated with titanium nitride. The letter “A” in the second option means aluminum alloying. Titanium nitride coating gives the tool a golden color and increases its wear resistance several times.

HSS-E-VAP

Steam oxidized drills. Drills of this group are covered with a film of oxides, which is created by steam oxidation - treatment with superheated steam in a special environment. The coating is black in color, reduces the adhesion of chips to cutting edges, and increases surface wettability with coolant. HSS-E-VAP drills are effective for drilling stainless steel and other tough alloys.

The hardness of drills made of high-speed steels according to GOST 2034-80 should be in the range of 63-66 HRC.

Cutting part

Cutting when drilling is carried out by two edges, which are formed by the intersection of the front surfaces of the helical grooves and the conical head of the drill. Strictly speaking, the cutting part is not completely conical: the back surface of the blade decreases, moving away from the theoretical cone at a slight angle.

The main sharpening parameter is the tip angle. For most applications it is around 118 o. For cast iron or hard bronze it can be reduced to 116 o. For brass, soft bronze, aluminum, angles of 120 o, 130 o, 140 o are used.

For drilling soft sheet metal, a special sharpening is used with curved cutting edges, a protruding pointed center and slightly protruding edge cutters. At the beginning of drilling, the drill is immediately clearly centered, then a contour is outlined, and after that the extraction of metal begins over the entire area of ​​the hole. As a result, beating at the inlet and biting of the edges at the outlet are eliminated.

For drilling steel and cast iron, double-sharpened drills are used. In addition to the apex angle of 116 - 118 o, the edges are ground off at the periphery, to a width of 0.2 diameters, at an angle of 70 - 75 o. There are other forms of sharpening for specific applications.

Drill steel grades - which ones are better?

Nowadays, buying a high-quality metal drill is a real problem; most drills are Chinese, their quality leaves much to be desired.
The quality of a drill depends, first of all, on the grade of steel from which the drill is made. Most modern metal drills are made from R6M5 steel, although the difference between modern drills and drills from the USSR (with a quality mark) is simply huge, Chinese drills instantly roll up and it is impossible to drill even an ordinary corner made of 3mm iron with them. One drill is enough for several holes. However, there are also high-quality drills that last a long time.

Let's look at the steel grades, because the quality and durability of the drill depends on this.

P18 is now a legendary steel. Containing 18 percent tungsten, this steel supports metal processing even at high speeds. Drills made of P18 steel do not overheat, endure for a long time and drill well. True, finding the real ones is a whole problem. In Soviet times, r18 steel was used very widely for the manufacture of metal-cutting tools, but after the 70s, tungsten reserves were depleted and it was replaced by steel with a lower tungsten content - r6m5.

R6M5 - 6 percent tungsten, 5 percent molybdenum. Standard steel for metal-cutting tools. If the drill for metal is a Soviet one made from R6M5, then it is perfect for everyday use at home; such drills last for a long time, although they cannot drill through more hardened iron. The following drills with the addition of cobalt are suitable for this.

R6M5K5 is the same as R6M5, only 5 percent cobalt is added, which makes these drills even stronger and more durable. Cobalt drills are suitable for drilling where high temperatures are generated during drilling. Photo:

Excellent for drilling stainless steel and other hardened steels. In general, if ordinary drills do not take iron, then buy one with cobalt, you will feel the difference.

HSS is a foreign analogue of high-speed steel, translated as High Speed ​​Steel, that is, steel for working at high speeds. HSS drills are similar in composition to the standard P6M5 high-speed cutter.

By the way, hss also comes with the addition of cobalt; drills are marked HSS-Co. Drills with this marking will be identical to our R6M5K5. Drills with cobalt - for drilling stainless steel and other durable steels.

It is also worth mentioning specialized drills for porcelain tiles, they are soldered and also come with crowns, if you are looking for information, follow the link, I prepared an article at the request of workers.

In general, if you decide to buy high-quality drills for your home, then I would recommend first asking around for drills from the USSR era; if they have a quality mark on them, then this is generally better than that. Soviet ones are inexpensive, you can even look at flea markets, you can probably find something there too.

Sovdepov drills are an excellent tool. If you take imported ones, then they cost a lot, for example, 6 mm HSS-Co drills cost around 70-80 rubles, while a similar Soviet one can be bought for 20-30 rubles.

Types of drills for metal

Metal drills differ from each other in several ways: manufacturing method, shank shape, scope of application, and, of course, diameter. First, let's look at what types of metal drills there are based on their design features. Here are their main types:

• Spiral or screw. Such metal drills are distinguished by the fact that they have the same diameter along their entire length and are used to produce both through and blind holes. The drill consists of a cylindrical working part with a pair of helical cutting edges and grooves along which the chips flow away.
• Stepped. Unlike the first type on our list, these drills are not cylindrical, but conical, so they can be used to drill holes of different diameters without changing the cutting tool. The main advantage of step drills is their versatility, however, they are designed to work mainly only with sheets of metal, since they cannot drill a hole in a metal workpiece thicker than 2 mm.
• Crowned. Designed for making large-diameter holes or when drilling several sheets of metal at the same time, the so-called multi-layer hole making. Such drills differ in the frequency of cutting edges and are made of high-speed steel.
• Countersink. Also made in the shape of a cone. These are metal drills that are intended for countersinking, that is, this type of mechanical cutting in which both cylindrical and conical holes are machined to increase their diameter.

It should be noted that these are only the main groups of drills, each of which has its own subtypes. So, before choosing a drill for metal, you should decide which shank, or in other words, the part of the drill that is fixed in the chuck, will suit you best. Based on this feature, metal drills are divided into three types: with a cylindrical shank, hexagonal and conical. The first of them is the most popular and widespread, suitable for almost all drilling tools. Tapered shank drills are mounted without a chuck at all on some types of drills or drilling machines.

In addition, according to the characteristic features of their manufacture, metal drills are:

• Solid. As is clear from the name, such metal drills are made from the same material. This type includes screw drills.
• Welded. They differ from the previous type in that they are made of two different types of steel. This manufacturing method is used for large diameter drills.
• Carbide. The tip of such metal drills is made of a carbide plate made of a special VK8 alloy and has a special one-sided sharpening angle. Such features allow the drill to cope with the strongest metals. Carbide body drills even allow you to change used inserts without replacing the drill itself.

As a rule, all the necessary information about metal drills is applied to the drill itself. By understanding the markings, you can easily choose metal drills that are best suited for a particular type of work. In addition, the marking of the drill will tell you what material it can handle.

Characteristics of HSS steels

HSS steels are divided into three groups:

• Tungsten (T);
• Molybdenum (M);
• High-alloy high-speed steels.

Tungsten steels are practically not used today due to the high cost of tungsten and its shortage. The most common are T1 general purpose steel and T15 vanadium cobalt steel. T15 is used for tools operating under conditions of high temperatures and wear.

Molybdenum group steels have molybdenum as their main alloying element, although some contain equal or greater amounts of tungsten and cobalt. Steels with a high content of vanadium and carbon are resistant to abrasive wear. A series of steels starting from M41 is characterized by high hardness when operating at high temperatures (red resistance). Molybdenum steels are also used in the manufacture of tools operating in “cold” conditions - rolling dies, cutting dies. In such cases, HSS steels are hardened to lower temperatures to improve toughness.

Table of common chemical compositions of HSS steels. Domestic analogues.

Not all analogues may be indicated in the table, since at present there may be a large number of borrowed, non-governed brands.

A cutting tool made with tungsten content (W) will have a very useful quality for the tool - red resistance. It allows tools to maintain a sharp cutting edge and hardness at red-hot temperatures (up to 530°C). Cobalt further increases the red hardness and wear resistance of HSS steels.

M1. Used for the production of drills for a wide range of applications. M1 steels have lower red resistance than M2 steels, but are less susceptible to impact and are more flexible, making them suitable for general work.

M2. Standard material for making tools from HSS steels. M2 has good red hardness and retains its cutting edge longer than other HSS steels with lower tungsten content. Typically used for the manufacture of tools for high-performance machine work.

M7. Used for heavy-duty drills for drilling hard sheet metal. Typically used where flexibility and extended service life are equally important.

M50. Used to make drill bits that are used for drilling on portable equipment where breakage due to bending is a problem. Does not have the same red resistance as other HSS tungsten steels.

M35. M35 steels have increased red resistance compared to M2. At the same time, cobalt slightly reduces impact resistance.

M42. M42 “Super Cobalt” steels have excellent abrasion resistance and good red-hardness. Used for work on viscous and complex materials.

What steel are metal drills made from?

The vast majority of metal cutting tools are made of high-speed steel, which may have various impurities, such as tungsten, cobalt, chromium, vanadium or molybdenum. The presence of one or another additional metal in the composition of high-speed steel can be understood from the markings of the drill. So, the letter M indicates the presence of molybdenum in the alloy, the letter F indicates that the alloy contains at least 3% vanadium, and if the letter P is present in the marking, then this is a sign that the alloy contains tungsten. It should be noted that chromium and carbon are not marked.

What is high speed steel? This is a type of steel that has ultra-high hardness, resistance to fracture and outstanding red-hardness. Thus, conventional carbon tool steels are not capable of providing high drilling or cutting speeds, but high-speed steels, thanks to alloying with the above-mentioned impurities, successfully cope with such extreme conditions.

In addition, not only the markings, but also their color can tell something about the materials from which drills are made. So, bright golden indicates that the drill is coated with titanium nitrite. Such drills have a long service life due to their increased wear resistance. And the black color of a drill, for example, indicates that it has been treated with steam, which also improves the quality of the cutting tool.

Sharpening a drill for metal

Not everyone can afford to buy new drills every time they become dull. Moreover, a high-quality metal drill, and not a cheap Chinese knockoff, is quite expensive. The good news is that with basic skills and a sharpening machine, you can sharpen a drill at home, thus avoiding unwanted financial expenses. Even if you don't have a sharpening machine at home, a regular drill and sharpening wheel will do the job. When sharpening a drill, you need to keep in mind that not only the drill head should be processed, but also the entire side cutting edge.

The density of the metal is so high that special tools and mechanisms must be used to process it. In order to make a hole in this material, drills and drilling machines are used, in which drills are the main cutting element.

Which metal drills are better? It is not easy to determine, because there are no universal products that would be suitable for processing all types of metal products. An experienced craftsman will be able to “by eye” determine the type of metal and quickly select the appropriate cutting tool for processing.

A beginner in this business needs to start with the basics. First, study the classification of drills and their scope of application, because the best models are products that are ideal for processing a specific type of metal.

What kind of drills there are, how to choose a suitable product for the job based on markings and appearance, find out in the article.

What is a shank and what are they?

The shank is the part of the drill that is clamped by the drill or hammer chuck. At first they were of the same type - tetrahedral, placed in the hole of the drill chuck and secured with a screw. Later, improved types of shanks appeared, used for various types of tools.

1. Cylindrical - found most often. As a rule, such products have the same base size and drill diameter. Sometimes there are models in which the shank is thicker or thinner than the drill. The disadvantage is that the shank slips, which makes it impossible to transmit a large torque to the drill. Advantage - if the drill jams in the working surface, the drill will be protected from damage;
2. Hexagonal (aka hexagonal and hex) shanks - suitable for various types of drills. Disadvantage: insignificant accuracy when using a ¼-inch holder;

This shank shape fits almost any drill model

Shanks designed specifically for rotary hammers

These shanks provide the greatest torque

Types of drills for metal

To choose the best models, you need to understand the types of drills.

Spiral

Classic, cylindrical drills that are most often used for drilling metals. Typically, spiral products are made of HSS steel.

The material is a high-quality cutting type of steel, so the gimlets made from it are highly durable and durable.

Conical (stepped)

The cutting surface has the shape of a cone, which is why this type of drill got its name. Conical drills are used to make holes in thin metal, as well as to correct defects from other cutting tools.

What are the best step drills to choose? Depends on the type of metal being processed. If the density of the workpiece is too high, then it is better to purchase more expensive, golden-colored products.

In everyday life, this type of drill is rarely used. If you need to frequently drill thin metal sheets or process soft materials, then despite the relatively high cost, it should be purchased for your home workshop.

Core cutters (annular cutters)

The cutting tool is a cylinder with a cutting edge, which is used to cut metal.

The energy consumption for making a hole in this way is several times lower, due to the small contact area of ​​the tool with the surface being processed.

The advantage of using this type of drill over others is the production of large diameter holes. In this case, it is possible to obtain better quality edges than when working with spiral models.

Feathers

A special type of flat gimlet with replaceable working edges is used for drilling metal. Such products allow you to make high-quality, perfectly straight holes.

The absence of distortion during the drilling process and the ability to make a large-diameter hole in various metal structures allows many craftsmen to abandon the use of spiral products.

The low cost of feather drills allows in many cases of metal processing to call them the best for drilling holes.

These are the main types of drills used for making holes in metal structures.

Features of heat treatment

The result of high-temperature processing of high-speed steels is a change in the structure of the material to obtain certain physical and mechanical properties required when working with this tool.

Annealing

HSS steel after the rolling and forging process acquires increased hardness and internal stress. In this regard, the workpieces are preliminarily annealed. Annealing relieves the internal stress of the material, improves machinability and prepares it for hardening.

The annealing process occurs at a temperature of about 850-900°C. However, one should be wary of excessively increasing the temperature and duration of exposure, because this may cause the steel to become more hard. Due to the reduced thermal conductivity of the alloy, heating is carried out slowly and evenly.

The products are loaded into the oven at a temperature of 200-300oC, while subsequent heating is increased at a rate of 150-200o/hour. The process ends with slow cooling: first in an oven to 650 ° C, and then to room temperature in the open air.

Machine-building plants subject a small number of workpieces to isothermal annealing. They are heated to 880-900oC for a short time, and then transferred to an oven with a temperature not higher than 720-730oC for 2-3 hours. To protect against the appearance of excessive internal stresses, the workpieces are cooled in an oven to 400-450°C and then left in the open air.

Conventional annealing takes longer than the isothermal process. Subsequently, the workpieces undergo mechanical processing, and then the tool undergoes the final heat treatment process - hardening and tempering.

Hardening

Tools made of high-speed steel are hardened at temperatures above 1300°C. After the hardening process, repeated tempering occurs at 550-560°C. This temperature is necessary to dissolve a large number of carbides in the austenite to obtain highly alloyed austenite.

With further cooling, highly alloyed martensite is obtained, which contains large amounts of tungsten, vanadium and chromium. Martensite does not disintegrate when heated to 600°C, which gives high-speed steel red-hardness.

To obtain high red-hardness values, the temperature during hardening must be very high. However, there is a limit, when exceeded, rapid grain growth begins in high-speed steel and melting occurs.

Vacation

Hardened high-speed steel must undergo a tempering process. At a temperature of 550-560°C, a multiple process is carried out at intervals of 1 hour. The purpose of tempering is to transform austenite into martensite. High speed steel goes through two internal processes:

1. When heated and subsequently tempered, ground carbide is released from the retained austenite. As a result, the alloying of austenite is reduced, which facilitates easy transformation into martensite.
2. During cooling at 100-200°C, martensite is obtained. This also relieves the internal stress that arose during hardening.

Nowadays, factories most often use the process of accelerated tempering of steel, which takes place at elevated temperatures.

Classification of drills by material of manufacture

Which metal drills are the best for drilling particularly strong alloys is quite simple to answer:

1. To process such material, you should choose products that have a plate of increased hardness on the cutting edge. Such gimlets are the best for processing hard alloys.
2. The price of such products is low due to the fact that the main body of the cutting tool is made of ordinary tool steel.

Drills made of metal alloyed with cobalt have good characteristics.

They can withstand increased mechanical loads and excessive heating of the working surface during operation. The cost of the products is high, but if it is necessary to make holes in a hard alloy, then cobalt analogues are the best for performing such work.

Titanium drills are not inferior in strength to cobalt drills, and when drilling alloy steels and non-ferrous alloys they show even better results.

Marking of cutting products

Marking drills for metal is necessary to determine the type of steel from which the cutting tool is made. The product also indicates its diameter, accuracy class and manufacturer (country). Only spiral gimlets with a diameter of less than 2 mm are not marked.

In other cases, drill markings may have the following meanings:

• P9 - made of high-speed steel with a tungsten percentage of 9%.
• P9K15 - indicates the presence of cobalt in the high-speed steel in an amount of 15%.
• Р6М5К5 - indicates the presence of a complex composition of cutting steel containing tungsten, cobalt and molybdenum.

Imported products have the HSS designation, which can be used to determine the composition of the material from which the drill was made. The HSS drill, which will be explained below, is used with an additional letter, which determines the presence of alloying metal.

• HSS-E - contains cobalt. Used in processing metals of high viscosity.
• HSS-Tin - has titanium coating, which significantly increases the hardness of the working surface, and the temperature resistance of the material increases to +600 degrees.
• HSS-E VAP is a cutting tool used for processing stainless materials.
• HSS-4241 - designed for drilling aluminum.
• HSS-R - have maximum strength.

By marking the cutting tool, you can determine for what metal and in what mode the drill can be used. If the marking is not visible, then the purpose of the drill can be determined by the color of the product.

Visual identification of drill type

By the appearance of the cutting gimlet, you can determine the type of material from which the products are made and thereby find out the mechanical strength of the sample. By color you can determine the composition and quality of workmanship.

Grey

Gray drills are made of metal that has not been subjected to any additional processing.

The quality of the tool, in this case, leaves much to be desired, but for one-time use such products are quite suitable.

Black

This color indicates that the tool was treated with superheated steam. During processing, the product acquires greater strength.

It perfectly tolerates numerous cycles of heating and cooling of the metal, and also maintains the sharpening of the working surface for a long time.

The price of black metal drills is not much higher than gray products, so if you have a choice, you should give preference to tools of this type when purchasing.

Dark golden

This color indicates that the cutting tool has been tempered. This type of processing significantly increases the mechanical strength of the product as a result of reducing internal stresses.

With a tempered drill, you can successfully process high-strength metals, so if you are drilling too hard alloys, it is recommended to purchase a similar model.

Bright golden

The bright golden color indicates that metal made with the addition of titanium was used in production.

Despite the high cost of such models, it is much more practical to purchase a high-quality drill than to use cheap cutting tools, which will need to be used in large quantities for complex work.

Thus, it is easy to determine the quality of products by appearance and decide which metal drills are best to buy.

Classification by size

To choose the best drill and not overpay, it is enough to know what length sizes these products are usually divided into. If drilling metal does not require making deep holes, then purchasing models that are too long will lead to cost overruns.

It is customary to classify drills by length as follows:

1. Short, 20-131 mm long. Tool diameters are in the range of 0.3-20 mm.
2. Elongated, length is 19-205 mm, and diameter is 0.3-20 mm.
3. Long series with a diameter of 1-20 mm and a length of 56-254 mm.

When performing drilling work of various depths, you should select the tool that is most suitable for the specific task.

Tips for choosing

To choose the right drill, you need to pay attention to important points

• Study the characteristics of the material and the capabilities of the drill so that the tool meets the requirements of the work being performed.
• Look at the color of the product. It can talk about how the metal was processed.
  steel color indicates that no heat treatment was performed;
• yellow – the metal has been processed, internal stress in the material has been eliminated;
• a bright golden hue indicates the presence of titanium nitride, which increases wear resistance;
• black – the metal is processed with hot steam.
• Study the markings to find out the type of steel, diameter, hardness.
• Find out about the manufacturer, consult with specialists.
• Study the issue of tool sharpening.

Often drills are sold in sets, for example, with different diameters. The question of purchasing such a tool requires an understanding of what purposes the drill is required for and how many options can be used.

To learn how to make a device for sharpening a drill on a grinder, see the video below.