Today everyone home handyman available necessary tool for metal cutting, drilling, stripping. But what if you need to drill a hole? large diameter? After all, the maximum cross-section of a conventional drill for a hand-held electric drill is only 20 mm.
Tools for drilling large holes
There are several ways to drill a hole with a diameter greater than 20 mm. For this, special devices are used:
- Cone drill. A large number of openings same size drilling won't work. But for home use quite acceptable. Maximum cross section- up to 40 mm. The thickness of the processed metal is 5-6 mm.
- Conical step drill. It is more convenient to use, since each step is formed through a smooth spiral transition. When drilling, this makes it easy to track the actual diameter of the hole. With its help you can drill a circle up to 40 mm in diameter on metal up to 6 mm thick.
- Bimetallic crowns - suitable for preparing holes up to 109 mm in steel products up to 5 mm thick. When working, it is strongly recommended to use specialized lubricating and cooling compounds, which will ensure maximum service life cutting tool. An adapter is also required to install the device on an electric drill. On average, using a bimetallic crown, you can drill 5-20 openings - depending on its quality, which, accordingly, is reflected in the cost.
How can you drill a large hole without extra costs?
For this method, you will need a small cross-section drill (5-6 mm is enough), as well as a milling cutter or a used grinding wheel (corresponding to or slightly smaller than the diameter of the hole) for an angle grinder. The option is more labor-intensive, so it takes much more time.
On a metal blank, 2 circles are drawn with a pencil:
- 1 - for the future hole.
- 2 - depends on the cross-section of the drill, that is, when using a 6 mm tool, the diameter of the intended circle will be 6 mm smaller than the previous one.
Along the 2nd circle it is necessary to mark 2 places in opposite places and drill holes with a 6 mm drill. From the resulting openings along the intended line you need to retreat approximately 3 mm and again mark the places for drilling. Holes are drilled along the entire circumference. If necessary, the remaining sections can be cut with a chisel.
The hole will be jagged, so it needs to be bored out. This can be done with an electric drill with a cutter, but it is much more convenient with a grinder using grinding abrasive wheels of a suitable diameter. Using a grinder, you can quickly and evenly bore a hole to the required diameter.
Therefore, you should not throw away used abrasive wheels for an angle grinder with a diameter of even less than 45 mm - they can always be useful on the farm.
How to drill big hole in metal
Now drilling large diameter holes in metal is not a serious problem. The main thing is to prepare well. Let's say you need to make a hole in a corner, channel or mortgage to strengthen building structure or hang a shelf, light fixture or conduit. That is, to do this not in a workshop or workshop, but directly on site. The easiest way to drill in such conditions is to use an electric drill. But, imagine how much pressure needs to be applied to it to drill a hole with a diameter of 16 or 20 mm? The question is not rhetorical - the force will be about 40-50 kgf. This is not at all easy to achieve if the proposed hole is located above the level of the driller's shoulders. Even 10 years ago, when such a task arose, even professionals resorted to an autogen and, just imagine, to drilling small holes around the circumference of a large one. Today there is a completely professional solution for this - core drilling, which ensures the production of holes of 11 quality.
However, many are sure that core drilling is a rather expensive method, economically beneficial only for industrial volumes. Is this statement true? Partly. Today, you can choose several options for tools and equipment for drilling holes in large-diameter metal without drilling. In this case, the cost per hole will be justified even when drilling only a few holes.
Let's consider what are the tool options for drilling? through holes large diameter in metal offers the market. For comparison, we take a diameter of 51 mm.
Firstly, this bimetallic crowns. We have a choice of samples from the cheapest ones, which are immediately sold in sets and cannot be accepted by us in this review for the reason that their purpose is to drill out wood, and even if they can drill through a sheet of metal, it will not be thicker than 0.5 mm . At a price of 240 rubles, products with a wall thickness of 1-1.2 mm start, often marked HSS - Co 5% and even HSS - Co 8, but judging by the fact that drilling one hole in stainless steel takes more than one such crowns, there may be no cobalt there at all. Twice as expensive bits of more decent quality, which really allow you to drill stainless steel and ordinary steel a few millimeters thick. Bimetallic crowns of this level allow you to drill 5-20 holes in a steel sheet 5 mm thick. At the same time, the use of any lubricant-cooling composition ensures the achievement top bar this range. At the third stage there are bimetallic crowns worldwide famous brands, which are still twice as expensive, can be equipped with special devices for quick change in the drill, but their service life is not much or does not exceed the average price level.
Drilling large diameter holes in steel sheets thickness of more than 5-6 mm for bimetallic crowns is very difficult, although sometimes you can hear a different opinion. It is based on data on the full drilling depth of such crowns - 35-38 mm. As a rule, only sellers of bimetallic crowns, who do not have a more worthy tool in their assortment, risk advising drilling a 30 mm sheet or beam in this way. The fact is that the bimetallic crown does not have a chip removal groove, and as soon as the thickness of the metal being drilled becomes greater than the height of the crown tooth, problems with chip removal begin. In addition, the body of the bimetallic crown is not entirely cylindrical, this causes jamming in metal of considerable thickness.
Unlike bimetallic crowns, crowns with carbide teeth provide more precision drilling. Carbide body hole saw- turned, while the bimetallic crown is rolled from tape and welded into a ring. There are several types of carbide drill bit designs. Without delving into the types of shanks and types of fastening, we will only analyze cutting part. The most expensive part of the crown is the carbide teeth. The quality of the material greatly influences the drilling speed, impact resistance, bit life and the ability to drill alloy steels with a high chromium content.
The second feature that you need to pay attention to is the shape of the tooth and its size. For drilling thin sheet steel, thin stainless steel and non-ferrous metals, a narrow tooth with a flat profile, slightly beveled inward, is used. Such crowns also do not have a chip removal groove, and they will not be able to drill into metal thicker than the height of their tooth. The price of such bits is two to three times higher than that of bimetallic bits, depending on the design of their body; they can be designed for drilling flat materials or for drilling pipes and profiles. Since these are professional samples, at present their counterfeits are rare, and almost all samples found on the market are of acceptable quality, but excellent quality ones should be chosen from manufacturers specializing in these products.
Thicker metal can be drilled with crowns with teeth of variable sharpening profile. In such crowns, every second or, as a rule, one of three consecutive carbide teeth is sharpened in its own way. This ensures soft cutting, no vibration, reduced load on cutting edges and, as a result, an increase in the resource of the crown. Such crowns have a short or long chip removal groove that extends almost the entire height of the wall. The first version of the bits allows you to drill metal up to 12 mm thick, and more powerful bits with a developed chip removal groove - up to 25 mm. It is this version of the tool for drilling holes in large-diameter metal that is the most progressive, providing the best performance and quality. The price of such crowns is 20-30% higher than that of thin-walled ones and in absolute value is 1880 - 1910 rubles, as we agreed, for a crown with a diameter of 51 mm. As elsewhere in nature, there are deviations in one direction or another up to 2 times, but, as usual, consideration builds a golden mean.
An option in which the metal is quite thick, say 10 mm, and the hole diameter is 20-25 mm can be solved with a carbide crown with a pilot drill. A drilling machine with a magnetic sole is recommended as a drive. but you can also use an electric drill. With the mentioned machine, the investment will be 21,164 rubles excluding VAT, and with a drill - 5,000 - 5,500 thousand. 
For a hole with a diameter of 50-60 mm, with such a metal thickness, the use of a magnetic or stationary drilling machine. A large load determines the high cost of investing in equipment, and together with a crown will be about 56,000 rubles, or, the option with a magnetic stand of a drilling machine and a separately purchased drill, about 50,000. Drilling such holes with a drill by hand is not only difficult, but also dangerous .
Drilling large-diameter holes in metal up to 5 mm thick with a hand-held electric drill is not difficult when using both bimetallic and carbide bits. The choice of tool depends on the required accuracy. When drilling holes with a bimetallic crown, the ovality of the holes and the increase in diameter from the desired value can reach 4% or in absolute terms - 2 - 3 mm. When drilling with a carbide crown - only 0.6 - 1 mm. In addition, all of the carbide bits presented in the review, and almost all of the bits available on the market for metal, also drill stainless steel.
Drilling holes in metal - tools and accessories
Metal processing is carried out not only in industrial conditions. By doing repair work on a car, manufacturing structures for personal plot or carrying out home renovations, it is necessary to drill holes in the metal. Most often used at home hand drill.
This universal tool requires certain skills to work with solid products. You can purchase or make your own machine for drilling holes in metal, but this is not a cheap pleasure. 
The technology of drilling holes in metal is to remove a thin layer of material due to simultaneous translational and rotational movement drill.
The main condition for high-quality and safe (for the tool) processing is keeping the chuck axis in a fixed position. Using a machine is easy to maintain straightness, which is not the case when working with hand tools.
If you are not confident in the steadiness of your hands (this is a normal situation for ordinary person), for drilling at right angles, mechanical assistants (conductors) are required.
Let us immediately make a reservation that additional conductors are required only in the case when the thickness of the metal exceeds the diameter of the drill.
If you are making a hole in a thin steel plate, straightness does not matter.
Devices for drilling perpendicular holes
There are several types of guides for hand-held electric drills. Power-driven tools are not suitable for working with metal, especially when it comes to precision. 
- Drilling jig. It is made in the form of a housing that is easy to hold, inside which there are guide bushings for drills of various diameters.
The material of the bushings is harder than the tool, so the holes do not wear out. By installing the jig exactly above the center of the intended hole, you don’t have to worry that the drill will “lead” away from the given direction.
This device is especially useful when drilling perpendicular holes in pipes of small diameter, when the tip tends to slip off the cylindrical surface. 
The sole is placed on the workpiece, held by the handle with the second hand. The drill moves strictly vertically, preventing distortions and drifts of the drill.
The design can have a corner holder for small-diameter pipes, which makes the device more versatile.
In the presence of rotary mechanism, you also get a device for drilling holes at an angle. 
True, it will not be possible to drill metal in this way; lateral loads will quickly break the drill.
The carriage with the tool attached (at the same neck) moves along the rod using a lever. The workpiece is held firmly on the sole using a vice or clamp. The quality of drilling is very high, but the cost of the device is considerable. Although, compared to a drilling machine, it is inexpensive.
You can make a device for holding the drill at a right angle yourself. It is enough to drill holes of various diameters in a block of durable material, for example - textolite or ebonite.
Just don’t count on lateral support - it’s more of a “device” for visual control. If the drill deviates laterally, it will quickly break the guide hole in the jig.
The next problem is drilling deep holes
It would be technologically correct to use lathe. Moreover, when processing cylindrical parts(for example, a gun barrel), the workpiece rotates, but the drill remains stationary. Cooling and forced removal of chips from the hole are required.
For this purpose, deep hole drills have special grooves on the surface, or the drill is periodically removed from the workpiece to clear chips.
At home, be sure to use drill guides. Craftsmen recommend not drilling holes with a depth of more than 2/3 of the length of the drill. You can use ordinary water for cooling; the drill is periodically removed from the hole to clear chips and cool.
Important! When drilling in several approaches, it is unacceptable to change the angle of the drill. Otherwise, you can “screw up” the workpiece.
The use of special long drills requires special technology. 
As soon as the cutting part, together with the retracting edges, disappears into the hole, the chips will clog the grooves and block rotation. Therefore on last stage removal of the drill and cleaning of chips is performed more often.
Drilling large diameter holes in metal
Drilling large holes in metal with a bimetallic crown - video
This procedure is even more complicated than deep drilling. Drilling large holes is done either with a crown (for small thicknesses) or with a regular drill in several stages.
The technology is the same as in the phased passage. You push the drill bit into the hole until you get the size you want.
Review of conical step drills and tips for their use - video
A few more examples of using a step drill in everyday life
Drilling with a step drill in metal 10 mm thick
We have discussed how to choose a tool for drilling holes. Now let's talk about general principles metal processing:
- The center of the future hole is “pierced” with a center punch. The tip of the drill rests on the hole during the first revolutions. Of course, if you have guides or a conductor, this is not necessary
- To achieve high accuracy (in diameter), you should choose a drill 0.1-0.3 mm smaller. Due to slight vibration in the chuck, the diameter increases slightly
- Use lubricant to reduce friction and cool. A regular one will do. water or machine oil
- At the first sign of dullness of the drill, stop working and sharpen the edges. Otherwise, you can not only lose the tool, but also damage the workpiece
- When drilling hollow workpieces (pipes, boxes), it is advisable to place a wooden spacer inside the workpiece
- To drill blind holes, use a stop ruler with markings. If your drill is not equipped with a stop, wrap an indicator ring around the drill using light-colored tape.
Interesting video on the topic: How to drill square hole in metal
Alexander | 04/24/2017 11:09
Review of conical step drills and tips for their use.
Very poor review. No recommendations for use.
These drills should be operated at low speeds. About 200.
At high speeds (from 400 and above), they “lick” and become unusable.
These drills are designed more for sheet cold-rolled metal up to 3 mm.
sposport | 04/24/2017 14:50
Hello, Alexander. I understand that you are talking about a video review of conical step drills? Because the topic itself is much broader. Thanks for your comment. Let's choose a more interesting review.
How to make a large hole in metal
Large hole in metal
If you need to drill large diameter holes, do not rush to spend money on a tool. Consider all options. It is possible that a tool that is suitable in one case is completely useless in another.
Cone drill
The drill is more suitable for home use. Because drilling a large number of holes of the exact diameter will be very difficult.
In this case, it is better to use a tapered step drill.
Cone step drill
The most popular are drills with a diameter of 0t 6 to 30 mm. (less often up to 40 mm.) in increments of 2 mm. That is, 6, 8, 10, 12 mm. etc.
Typically used for drilling sheet metal up to 2 mm thick. and plastic up to 5 mm thick. The undeniable advantage of this drill is that for 1500 ─ 3000 rubles. you buy about 10 ─ 15 diameters.
If when drilling plastic, the drill behaves very well, then drilling holes of large diameters in metal is associated with some difficulties:
with large volumes of work, the 6 mm drill quickly becomes dull;
Drilling large diameter holes requires significant physical effort.
Metal crown
Large holes in metal, plastic, wood, etc. with a diameter of 19 to 102 mm. Conveniently done using a bimetallic crown from Hilti.
The bits performed very well when drilling a large number of holes for fittings in metal cable boxes (metal thickness 2 mm).
A clear advantage is that the crown is collapsible. If the centering drill becomes dull or breaks, the cost of replacement is about 250 rubles.
But for each diameter you will have to use a separate crown, the price of which (depending on the diameter) is from 400 to 1200 rubles. Add 1000 rubles here. to the adapter.
Hole press
The tools discussed above for drilling large holes in metal have one significant drawback: a very sharp edge. When laying cables or wires without fittings, this can become a serious problem.
To get a perfectly smooth edge, it is better to use a hole press. It costs a little more than 11,000 rubles. But in the set you get 8 nozzles with a diameter from 16.2 to 47 mm.
Without special effort a large number of holes are punched in metal up to 3 mm thick.
One clarification: the instructions for the PGRO-60 KVT press say that after punching a hole, you need to stop pumping. As practice has shown, it is better to do another compression with the handles of the press. This makes it easier to remove the cut metal from the matrix.
How to drill metal with a drill - detailed step-by-step instructions
Drilling metal with a drill is somewhat more difficult than wood, brick or concrete. There are also some peculiarities.
For convenience, we have combined practical advice on this type of work into step-by-step instructions.
- You will need the following tools: drill, drill, coolant (preferably machine oil, but water can also be used), punch, hammer, safety glasses.
- When drilling metal on a horizontal surface, place it under the product wooden block and fix it as best we can. When working in a vertical position, rigid fixation is extremely important, since drilling must be strictly perpendicular.
- We make markings, then use a center punch and a hammer to mark the center of the future hole.
- Pour coolant into a small container.
- We put on safety glasses.
- Let's start drilling. Do not put strong pressure on the drill, because it works better at low speeds. If the drill is powerful, then the method of short-term activation is suitable until the tool has time to reach maximum speed.
- Don't forget to cool the drill as often as possible .
- When drilling occurs not strictly perpendicularly, but at an angle, there is a high probability that the drill will jam. If this happens, put the switch in the reverse position. This way you will avoid injury and will not break the drill.
- If everything was done correctly, then even in living conditions Using a low-power drill, you can drill a hole in metal up to 5 mm thick inclusive and with a diameter of up to 10-12 mm. Oh more complex tasks we'll tell you below.
Metal drilling work
Is it possible to drill into metal with a concrete drill?
It is possible, but this is in case of extreme necessity for shallow holes with a small diameter. Unprofitable.
It is better to use either standard metal drills with steel grade R6M5 or improved ones - R6M5K5.
The letter K in the marking indicates that this is an alloy with the addition of cobalt. On the market you can find a drill called “Cobalt”. We will not vouch for all manufacturers, we will only note that reviews on practical application in the overwhelming majority of cases - positive.
How to drill with a step drill in metal?
Step drills are universal - just one can make holes of different diameters (from 2 to 40 mm). They are most effective when working with thin metal, when you need to get a neat edge. They are better fixed in the cartridge, they are easier to sharpen, and therefore when correct operation They last longer, but also cost more than usual. The principles of working with them are the same, but it is easier to drill large-diameter holes than with conventional twist drills.
Is it possible to drill metal with a Pobedit drill?
The principle of operation of drills for metal is to cut, and with pobedite soldering, crush materials. Brick, concrete, and stone are better suited for this. Therefore, as mentioned above, use a concrete drill. Of course, you can drill metal, but it will quickly become unusable and pobedit soldering will collapse.
What is the larger hole diameter? the lower the speed should be. The greater the depth? Therefore, you gradually need to reduce the pressure on the drill. With a drill diameter of up to 5 mm, the torque should not be higher than 1200-1500 rpm. Accordingly, 10 mm in diameter - no more than 700 rpm, 15 mm - 400 rpm.
How to drill holes in large diameter metal?
As a rule, most drills for household use have a power from 500 to 800 W, which allows you to drill holes with a diameter of up to 10-12 mm. In metal up to 2 mm thick, using step drills you can make holes up to 40 mm. With a thickness of 3 mm, bimetallic crowns are better suited.
When drilling deep holes with any tool, you may sometimes need a magnet to remove the chips.
Metal drilling process
Particular attention should be paid to safety precautions, be sure to protect your eyes from chips, and if there is distortion and jamming, immediately turn off the drill and change the torque to reverse movement.
In situations where there is no power or where the noise of the tool operating may disturb others ( read. When can you make repairs so as not to quarrel with your neighbors?)– ideal solution when drilling metal it will be manual mechanical drill, the so-called rotation. Low speed and pressure, no overheating, just what you need. Of course, there are also disadvantages - time-consuming and easy fatigue. In this simple “old-fashioned” way, you can drill holes with a diameter of up to 10 mm.
We hope our tips will be useful to you.
More information in this video.
Today, every home craftsman has the necessary tools for cutting metal, drilling, and stripping. But what if you need to drill a large diameter hole? After all, the maximum cross-section of a conventional drill for a hand-held electric drill is only 20 mm.
Tools for drilling large holes
There are several ways to drill a hole with a diameter greater than 20 mm. For this, special devices are used:
- Cone drill. It will not be possible to drill a large number of openings of the same size. But for home use it is quite acceptable. The maximum cross-section is up to 40 mm. The thickness of the processed metal is 5-6 mm.
- Tapered step drill. It is more convenient to use, since each step is formed through a smooth spiral transition. When drilling, this makes it easy to track the actual diameter of the hole. With its help you can drill a circle up to 40 mm in diameter on metal up to 6 mm thick.
- Bimetallic crowns - suitable for preparing holes up to 109 mm in steel products up to 5 mm thick. When working, it is strongly recommended to use specialized lubricating and cooling compounds, which will ensure maximum service life of the cutting tool. An adapter is also required to install the device on an electric drill. On average, using a bimetallic crown, you can drill 5-20 openings - depending on its quality, which, accordingly, is reflected in the cost.
How can you drill a large hole without extra costs?
For this method, you will need a small cross-section drill (5-6 mm is enough), as well as a milling cutter or a used grinding wheel (corresponding to or slightly smaller than the diameter of the hole) for an angle grinder. The option is more labor-intensive, so it takes much more time.
On a metal blank, 2 circles are drawn with a pencil:
- 1 - for the future hole.
- 2 - depends on the cross-section of the drill, that is, when using a 6 mm tool, the diameter of the intended circle will be 6 mm smaller than the previous one.
Along the 2nd circle it is necessary to mark 2 places in opposite places and drill holes with a 6 mm drill. From the resulting openings along the intended line you need to retreat approximately 3 mm and again mark the places for drilling. Holes are drilled along the entire circumference. If necessary, the remaining sections can be cut with a chisel.
The hole will be jagged, so it needs to be bored out. This can be done with an electric drill with a cutter, but it is much more convenient with a grinder using grinding abrasive wheels of a suitable diameter. Using a grinder, you can quickly and evenly bore a hole to the required diameter.
Therefore, you should not throw away used abrasive wheels for grinders with a diameter of even less than 45 mm - they can always be useful on the farm.
Often when working with wood and wood-based materials, it becomes necessary to drill an even round hole. You can use a jigsaw or a router, but such a tool is not always at hand or it is simply inconvenient to do the work with them. A woodworking ballerina can make the task easier.
What is a wood ballerina
Circular adjustable drill"ballerina" - a device that is designed for drilling round holes large diameter. The tool has simple design. It consists of a shank with a transverse rod on which movable carriages with cutters are attached. The rod has markings according to which you can set the required spread of the cutters relative to the center of the intended hole. A core drill is fixed in the middle of the shank. It serves as a centering element and support when drilling.
In addition to designs with two cutting elements located symmetrically, there are ballerinas with one cutter or even three. In the latter case, they are located on the base in the form of a disk with grooves.
Tool functionality
A high-quality ballerina is made of high-strength steel, which makes it possible to use the device in working with soft and hard wood.
This tool has an adjustable drilling diameter. This allows you to make holes of almost any diameter. The limitation of the drilling range depends on the size of the ballerina. Manufacturers produce devices with the following limits spread of incisors:
- from 30 to 120 mm;
- from 40 to 200 mm;
- from 40 to 300 mm;
- from 40 to 400 mm.
The maximum drilling diameter is limited by the rod on which the cutters are mounted. The minimum is the thickness of the shank.
The ballerina drill can be used in any places where the use of a jigsaw or hand router will be inconvenient. For example, this may be assembled and installed furniture, in the part of which it is necessary to drill a neat hole, given the limited space. Another example is an uneven (curved or concave) surface. It’s unlikely that you’ll be able to do everything smoothly and neatly with a jigsaw or milling cutter. It will be difficult to control the inclination of the tool relative to the surface. A ballerina can easily cope with this task.
Features of working with the tool
The principle of working with a circular drill is simple. A hole is drilled using a centering drill, and then the cutters are put to work. They gradually make a narrow groove, gradually cutting through the material in a circle to the full depth.
The materials used in working with the ballerina are varied: wood, fiberboard, chipboard, MDF, plasterboard, plastic. One common point is that the thickness of the part should be no more than 15-20 millimeters. This parameter is limited by the length of the incisors. Usually the manufacturer indicates the maximum drilling depth on the packaging. If you try to drill into thicker material, you may experience problems with ragged edges.
The use of a tool with one cutter is characterized by runout. This is caused by a lack of balancing relative to the longitudinal axis of the drill. The beating will be especially noticeable when cutting large diameter holes. Cut holes using a drill at low or medium speed. When working on a drilling machine, such problems do not arise.
Also, a laminated or veneered surface can cause inconvenience when working. After passing through the decorative layer, drilling proceeds without problems.
A feature of the circular drill can be considered the ability to adjust the diameter. The distance between the cutters can be set using a scale on a rod or more accurately using a caliper. This is convenient if you need to make a hole without gaps for a pipe or round part.
The spacing of the cutters relative to the center is adjusted individually. It is necessary to align the cutting parts as accurately as possible. This will eliminate unnecessary effort during operation and extend the life of the tool.
How to choose and what to pay attention to
Choosing a high-quality circular drill is quite easy. The main thing is to know the main points that you should pay attention to first, but also not to lose sight of the little things.
The design is very important point: a woodworking dancer comes with one chisel or two or more. For frequent use, it is better to purchase an option with two or three cutting elements. It is easier to work with such devices and the quality of the processing performed will be at an acceptable level.
It wouldn't hurt to replace it individual parts. Inexpensive circle drills can have a solid shank with a permanent center drill and rod.
Metal, its quality determines its strength and ability to withstand workloads. Quality tool made of high-strength steel or alloys. The shank and cutter holders are shaped using a machine tool. The rod is usually stamped and made of the same metal.
Cheap options often use soft metal or alloys, which can be brittle. Under load, parts may become deformed or break. Such a tool will not last long and it will also be difficult to achieve accuracy from it.
The quality of workmanship, the main feature is the absence of backlashes and distortions. All parts must fit together and be securely fastened with fixing screws.
The markings of a high-quality ballerina's barbell are stamped. Sometimes the divisions are highlighted with bright paint for better visibility.
Cutters, high quality cutting elements made from hardened tool steel. They are secured to the holders with rivets or soldering. Solid cutters with holders (made of the same metal) quickly become dull and are not durable.
Manufacturer, when choosing any tool and consumables, preference should be given to well-known and long-proven brands and brands. The most common are Topfix, Stayer, Irwin, Strum.
Purchasing an adjustable circular drill for use at home, or if you need to drill several holes, is completely worth it. This eliminates the need to purchase an expensive tool that may only be needed a few times.
Metal drills are selected based on the diameters of the holes and the properties of the material being processed. As a rule, they are made from high-speed steels, such as R6M5K5, R6M5, R4M2. Carbide drills are used to work with cast iron, carbon and alloy hardened steels, stainless steel, and other difficult-to-cut materials.
The power of the electric drill must be designed to drill a hole of the required diameter. Manufacturers of power tools indicate the corresponding specifications on the product. For example, for drills with a power of 500...700 W, the maximum drilling diameter for metal is 10...13 mm.
There are blind, incomplete, and through holes. They can be used to connect parts together using bolts, studs, pins and rivets. If the hole is drilled for the purpose of threading, it is worth turning Special attention to choose the drill diameter. Due to its beating, a hole in the chuck occurs, which must be taken into account. Approximate data are presented in the table.
To reduce the breakdown, drilling is performed in two stages: first with a smaller diameter drill, and then with the main one. The same method of sequential drilling is used when it is necessary to make a hole of large diameter.
How to drill metal correctly with a drill
The peculiarity of drilling metal with a drill is that it is necessary to manually hold the tool and give it correct position, as well as provide the required cutting speed.
After marking the workpiece, you should mark the center of the future hole. This will prevent the drill from moving away from given point. For ease of work, the workpiece should be clamped in a bench vice or placed on a stand so that it takes a stable position. The drill is installed strictly perpendicular to the surface to be drilled. This is important to avoid it breaking.
When drilling metal, you do not need to apply much pressure to the drill. On the contrary, it should decrease as you progress. This will prevent the drill from breaking and will also reduce the formation of burrs on the exit edge of the through hole. Care must be taken to remove chips. If the cutting tool is jammed, it is released by returning it to reverse rotation.
Selecting cutting mode
When using a tool from high speed steel, you can focus on the rotation speed according to the data in the table. When working with carbide drills valid values 1.5...2 times higher.
Drilling metal products must be done with cooling. If it is not used, there is a high probability that the tool will lose its cutting properties due to overheating. The cleanliness of the hole surface will be quite low. An emulsion is usually used as a coolant for hard steels. At home suitable conditions machine oil. Cast iron and non-ferrous metals can be drilled without coolant.
Features of drilling deep holes
Holes are considered deep if their size is greater than five drill diameters. The peculiarity of the work here lies in the difficulties associated with cooling and chip removal. The length of the cutting part of the tool must be greater than the depth of the hole. Otherwise, the body of the part will block the screw grooves through which chips are removed and liquid for cooling and lubrication is supplied.
First, the hole is drilled with a rigid short drill to a shallow depth. This operation is necessary to set the direction and centering of the main tool. After this, a hole of the required length is made. As you progress, you need to remove metal shavings from time to time. For this purpose, use coolant, hooks, magnets, or turn the part over.
Now drilling large diameter holes in metal is not a serious problem. The main thing is to prepare well. Let's say you need to make a hole in a corner, channel or mortgage to strengthen a building structure or to hang a shelf, lamp or pipeline. That is, to do this not in a workshop or workshop, but directly on site. The easiest way to drill in such conditions is to use an electric drill. But, imagine how much pressure needs to be applied to it to drill a hole with a diameter of 16 or 20 mm? The question is not rhetorical - the force will be about 40-50 kgf. This is not at all easy to achieve if the proposed hole is located above the level of the driller's shoulders. Even 10 years ago, when such a task arose, even professionals resorted to an autogen and, just imagine, to drilling small holes around the circumference of a large one. Today there is a completely professional solution for this - core drilling, which ensures the production of holes of 11 quality.
However, many are sure that core drilling is a rather expensive method, economically beneficial only for industrial volumes. Is this statement true? Partly. Today, you can choose several options for tools and equipment for drilling holes in large-diameter metal without drilling. In this case, the cost per hole will be justified even when drilling only a few holes.
Let's consider What tool options for drilling large-diameter through holes in metal does the market offer?. For comparison, we take a diameter of 51 mm.
Firstly, this bimetallic crowns. We have a choice of samples from the cheapest ones, which are immediately sold in sets and cannot be accepted by us in this review for the reason that their purpose is to drill out wood, and even if they can drill through a sheet of metal, it will not be thicker than 0.5 mm . At a price of 240 rubles, products with a wall thickness of 1-1.2 mm start, often marked HSS -Co 5% and even HSS -Co 8, but judging by the fact that drilling one hole in stainless steel takes more than one such crowns, there may be no cobalt there at all. Twice as expensive bits of more decent quality, which really allow you to drill stainless steel and ordinary steel a few millimeters thick. Bimetallic crowns This level allows you to drill 5-20 holes in a steel sheet 5 mm thick. At the same time, the use of any lubricant-cooling composition ensures that the upper limit of this range is achieved. At the third stage there are bimetallic bits from world-famous brands, which are still twice as expensive, can be equipped with special devices for quick change in a drill, but the service life is not much or does not exceed the average price level.
Drilling large diameter holes in steel sheets more than 5-6 mm thick for bimetallic crowns is very difficult, although sometimes you can hear a different opinion. It is based on data on the full drilling depth of such crowns - 35-38 mm. As a rule, only sellers of bimetallic crowns, who do not have a more worthy tool in their assortment, risk advising drilling a 30 mm sheet or beam in this way. The fact is that the bimetallic crown does not have a chip removal groove, and as soon as the thickness of the metal being drilled becomes greater than the height of the crown tooth, problems with chip removal begin. In addition, the body of the bimetallic crown is not entirely cylindrical in shape, which causes jamming in metal of considerable thickness.
Unlike bimetallic crowns, they provide more accurate drilling. The body of the carbide hole saw is machined, while the bimetallic bit is rolled from tape and welded into a ring. There are several types of carbide drill bit designs. Without delving into the types of shanks and types of fastening, we will only analyze the cutting part. The most expensive part of the crown is the carbide teeth. The quality of the material greatly influences the drilling speed, impact resistance, bit life and the ability to drill alloy steels with a high chromium content.
The second feature that you need to pay attention to is the shape of the tooth and its size. For drilling thin sheet steel, thin stainless steel and non-ferrous metals, a narrow tooth with a flat profile, slightly beveled inward, is used. Such crowns also do not have a chip removal groove, and they will not be able to drill into metal thicker than the height of their tooth. The price of such crowns is two to three times higher than that of bimetallic crowns, depending on the design of their body, they can be designed or. Since these are professional samples, at present their counterfeits are rare, and almost all samples found on the market are of acceptable quality, but excellent quality ones should be chosen from manufacturers specializing in these products.
Thicker metal can be drilled. In such crowns, every second or, as a rule, one of three consecutive carbide teeth is sharpened in its own way. This ensures soft cutting, no vibration, reduced load on the cutting edges and, as a result, increased bit life. Such crowns have a short or long chip removal groove that extends almost the entire height of the wall. The first version of the crowns allows you to drill metal up to 12 mm thick, and up to 25 mm thick. It is this version of the tool for drilling holes in large-diameter metal that is the most progressive, providing the best performance and quality. The price of such crowns is 20-30% higher than that of thin-walled ones and in absolute value is 1880 - 1910 rubles, as we agreed, for a crown with a diameter of 51 mm. As elsewhere in nature, there are deviations in one direction or another up to 2 times, but, as usual, consideration builds a golden mean.
An option in which the metal is quite thick, say 10 mm, and the hole diameter is 20-25 mm can be solved. It is recommended as a drive, but you can also use an electric drill. With the mentioned machine, the investment will be 21,164 rubles excluding VAT, and with a drill - 5,000 - 5,500 thousand.
For a hole with a diameter of 50-60 mm, with such a metal thickness, the use of a magnetic or stationary drilling machine is clearly required. A large load determines the high cost of investing in equipment, and together with a crown it will be about 56,000 rubles, or, option with magnetic drill stand and a separately purchased drill about 50,000. Drilling such holes with a drill by hand is not only difficult, but also dangerous.
Drilling large-diameter holes in metal up to 5 mm thick with a hand-held electric drill is not difficult when using both bimetallic and carbide bits. The choice of tool depends on the required accuracy. When drilling holes with a bimetallic crown, the ovality of the holes and the increase in diameter from the desired value can reach 4% or in absolute terms - 2 - 3 mm. When drilling with a carbide crown - only 0.6 - 1 mm. In addition, all of the carbide bits presented in the review, and almost all of the bits available on the market for metal, also drill stainless steel.