In this simple way, you can not only round hole in hardened steel, but also a hole of any other shape in extra effort. Chemical method will help you out and make things easier. The method does not require expensive chemicals, all ingredients can be found in any household.
It will take
I offer a simple method for making holes in high speed steel. For work you will need:- any product made of high speed steel;
- marker;
- nail polish;
- nail polish remover (can be replaced with white spirit or acetone. I chose the remover only because of the pleasant smell, and this is the same acetone);
- cotton wool;
- empty plastic container (bottle);
- salt;
- homemade device from a charger and two nails.
Making a hole in metal without a drill
We apply nail polish remover on cotton wool and degrease the surface of our workpiece.
We apply varnish to the desired area. Lacquer should be applied in a thick layer on both sides. Do not forget to carefully coat the ends. Leave the blank for 10-15 minutes for the varnish to dry.
On the dried surface, with a marker on both sides of the workpiece, I mark the place for the hole. I choose the place arbitrarily, now I need to show how a hole can be made in this way. For example, you need to put a regular factory rivet. The hole diameter should be slightly smaller than the rivet size.
Then, with a knife, remove the varnish inside the contour of the hole. Do this on both sides.
Pour water into a container and add 3 tablespoons of salt. The height of the water in the container should be 10 mm less than the height of the section of the workpiece covered with varnish.
I take a contraption made from a hair clipper charger and two nails. The nails will act as electrodes - I connected them to one contact. The other contact is just a bare, stripped wire. I use a 12V charger, but a regular mobile phone charger will do the job.
The stripped wire should be a plus, the electrodes should be a minus. We attach the positive wire with a clothespin to our workpiece. Then we lower the nails into the water.
You can make slots in the container to fix the position of the nails. Plugging the charger into an outlet. After switching on, the water around the electrode nails begins to bubble, and the cleaned mark under the hole turns black.
Note: to check the polarity of the wires, you need to connect the charger. If water begins to bubble around the nails, then this is a minus and you connected correctly. The appearance of bubbles in the water around the workpiece says that the minus is connected to it and it is necessary to throw the wires. The minus must always be connected to the electrodes and the plus to the workpiece to be etched!
We leave the container for one hour, 30 minutes after the start of the process, it is necessary to change the water. I turn off the charger and take out the workpiece.
A through hole was formed in the intended place. In order to make the hole diameter larger, the process can be continued. Or file uneven edges with a file.
This is how you can make the desired hole in the workpiece by etching high-speed steel with the help of the most common objects.
drilling through holes in metal blanks is produced with various tools using special techniques. Many professionals in the performance of engineering work have to drill holes in metal structures often. These items have high elasticity, which forces the use of special cutting devices when drilling.
Types of drills and devices for drilling in metal
Necessary devices for drilling metal products - electrical and hand drills as well as drilling machines. The working part of such devices is a drill of various shapes:
- spiral;
- screw;
- crown-shaped;
- conical;
- flat;
- cannon;
- rifle;
- centering;
- stepped.
Each drill has an individual marking, where the diameter of the section and the type of alloy from which it is made are indicated on the tip. To drill a hole of the required diameter, a drill bit a few tenths of a millimeter narrower is required.
Drills are also classified by length:
- short;
- elongated;
- long.
Some materials may require a specially ground diamond-tipped drill bit. Twist drills may not be able to cope with products made of thin sheet alloys. In some cases for drilling deep holes the product has to be fixed in a vice, stops, conductors, corners with fasteners. This is done for safety and high quality holes.
Hole drilling modes in metal products
For drilling through holes in metal products it is extremely important to prepare for the process. In the tool, it is necessary to correctly fix and direct the drill. It is necessary to adjust the frequency of rotation and other parameters. For products that are too strong, a low drill speed is recommended. An indicator of correct drilling should be a uniform long chip.
Hole types and drilling methods
In some work in production, the following types of holes in metal blanks are often needed:
- Through. Punches metal blanks completely. It is important to protect the surface of the machine from accidental exit of the drill outside the workpiece in order to avoid damage to the drill and the occurrence of burrs on the blank. Workbenches with holes are ideal for these types of work, where it is possible to put a wooden gasket under the workpiece. Holes in thin blanks are drilled with flat drills, because the twist drill can noticeably destroy the edges of the product.
- Deaf. Performed on required depth without penetrating the product through and through. In this case, an important point is measuring the depth, which is convenient to do by limiting the length of the drill with a sleeve stop or a drill chuck with a fixing stop. Professional machines equipped automatic systems feed to a given depth size, which allows you to fix the depth of the drill.
- Deep. This type of hole includes those drills whose length is five times the diameter. When drilling deep holes, it is necessary to periodically eliminate the resulting chips with the use of additional lubricants. It is often necessary to enforce cooling measures for the drill and the product itself, which rapidly rise to too high a temperature as a result of friction. This applies to workpieces made of high-strength alloys. For deep holes, twist drills are used.
- wide diameter. Drilling holes of large diameter in products of large proportions is a very responsible and time-consuming process. For such holes, conical, crown-shaped or step drills. Specialists carry out reaming at low tool speeds, trying to ensure the safety of the edges of the workpiece.
- Complex shape. Sometimes it is necessary to drill through or blind holes in workpieces of different densities under internal thread. Technology has to be divided into two steps: preliminary training platforms and drilling itself.
- Half. Half blanks are drilled, filling the cavities with wood. Stepped holes can be obtained by one of two techniques: reaming (passing a drill of a smaller diameter to the entire depth of the workpiece, followed by reaming with drills of a larger diameter) and reducing the diameter (drilling a hole of a larger diameter to the required depth, followed by replacing a drill of a smaller diameter). As a result, the hole is clearly centered.
Safety when drilling holes in metal workpieces
Start drilling holes in metal blanks with great care, avoiding the rapid destruction of the drill. Compliance with simple rules when drilling will ensure safety and guarantee the release of a quality product at the end of work:
- On the eve of drilling, it is necessary to carefully check the fixation of all fastening devices on the machine.
- You can start work in special clothes to prevent any elements from getting under the moving parts of the machine. Protect your eyes from metal shavings with special goggles.
- When the drill tip enters the metal workpiece, it should already rotate at low speed to avoid dulling.
- Come out with a drill drilled hole should be gradually, reducing speed, but not stopping completely.
- When the drill tip does not go deep into the workpiece, you will have to check the strength of the metal. When running over the surface with a file, it is possible to determine the degree of strength. If there is no roughness left on the grade, a diamond tipped drill or more solid material, and drill at low speeds.
- Drills of small diameter, which are difficult to fix in the chuck, are recommended to be wrapped around the tail with brass wire to increase the diameter of the girth.
- If the work is carried out with a polished workpiece, you can put a felt washer on the base of the drill to avoid damage when it comes into contact with the drill chuck.
- To fix metal blanks made of polished or chrome-plated steel, fabric or leather gaskets are used.
- When drilling deep holes, a small piece of compressed foam placed on the drill will blow off small metal chips. Also, the foam will make it possible to deepen the drill to the required mark in the production of blind holes.
The power of electric drills must be taken into account when drilling holes in metal workpieces of various hardness. Power tool manufacturers label their appliances with specifications on their body. For drills of different power, drills of the corresponding diameter are assumed.
You can entrust any, including drilling, to the specialists of Proflasermet. We will determine the required hole diameter and select suitable tool which we have a large selection of. As a result, you will receive perfect solution in short time.
Metalworking is carried out with a special cutting tool, with the help of machines and mechanisms. Drilling holes in metal is no easy task. This technological operation requires elementary knowledge about the material, machine tools and cutting technology. Sometimes it is difficult to choose a drill taking into account different degrees of metal hardness and choose cutting conditions.
Required Tools
Professional drills for metal(e.g. Bosch, Makita, Metabo or Hawera) are made exclusively from HSS. Some are covered with a protective layer, which increases their wear resistance when drilling.
Hand tools - a drill and drills should be chosen carefully. If there is no experience in this area, it is necessary to consult a store employee. Not always buying an expensive drill high class guarantees its long service life.
Compliance with the technology of obtaining holes in metal and a properly selected drill significantly increases its service life and protects against premature wear. Basic rules of operation cutting tool:
- Selection of a suitable type of gimlet for drilling metal of a certain hardness. Many manufacturers have developed entire programs by which you can choose the right tool.
- Selection of cutting conditions, setting the correct rotation speed.
- Properly selected feed, application of the appropriate pressure force on the cutting tool.
- Cooling application. An oil-based emulsion is recommended.
- Proper clamping of the material (e.g. in a vise).
- Fixing the drill to the stand, precisely and perpendicularly.
- The use of an extended set of gaskets when drilling through holes.
Technological process
Drilling is the process of removing small parts of the material being processed, chips, with the help of a drill. During drilling, the temperature of the workpiece rises. The cutting force leads to damage, the friction force causes a change in the geometry of the cutting edge, plus heat, as a result, the tool gradually blunts.
Most drills are made from high speed steel. with different content of cobalt. It is very important that it be sharpened correctly: the cutting edges are of equal length, the jumper between them is along the axis of the cutting tool.
This ensures that both edges will perform identical work during the drilling process. The drill will not have runout, the diameter of the hole will correspond to the size, the heating of the part and tool will be minimized.
Drill bits with chamfer correction have a smaller bridge, due to which the cutting edges are lengthened. Such drills can drill a hole without preliminary marking with a core.
The choice of drills depends on the type of work being done.. NWKa HSS Baildon drills are optimal for drilling:
- structural steel;
- cast iron;
- brass;
- bronze;
- aluminum;
- plastics;
- tree.
Metal drilling
A feature of the drills is the presence of a sharp edge that allows you to perform mechanical processing of the material. They have an equal diameter along the entire length, and the blade is sharpened at an angle of 118 °. The sharpening angle varies depending on the hardness of the material, for example, for alloy steel, it is 135 °. Drills of this type are made of HSS steel with a 5% cobalt impurity. They require cooling during operation. special drilling oil.
In order to drill a nozzle in metal evenly and accurately, it is necessary to use a guide device - a jig.
When drilling, it is best to apply as little force as possible. When drilling a through hole, when the moment of exit of the cutting tool is approaching, it is necessary to reduce the feed so that the part is not pulled out, the drill is not broken, and burrs are not formed.
To obtain a conical hole in the metal, a conical drill is used. It is used as independent tool. They can drill a cylindrical hole, turning it into a conical one. A conical hole in the metal is made on lathe to drill, bore the resulting nozzle with a cutter.
Cutting conditions
The most common mistake is too high drilling speed. The harder the material is processed, the lower the drilling speed should be applied. For example, in the case of drilling an 8mm hole in brass, the drilling speed should be 2500 rpm, for harder alloy steel, 800 rpm. best sign choosing the right drilling speed is a beautiful and long chip.
Depending on which tool to choose, cutting parameters are important. It is necessary to choose the right rotation speed and feed. The best parameters are provided by desktop drilling machines, but they can not be used everywhere. It is necessary to follow the principle that the lower the speed and the lower the feed, the longer the tool will last.
For example, take stainless steel, hole 8 mm, thickness 4 mm, lotion or oil for cooling, HSS drill, drill or drilling machine: The revolutions must not exceed 400 rpm, and the feed cannot be more than 0.10 mm / turnover. In other words, you can drill at up to 400 rpm. But this speed is not optimal. Therefore, it will be optimal, for example: 170 rpm, and the feed for every 30 revolutions is 1 mm (three times less than recommended).
Cooling of the drill during the drilling process is very important. Use emulsions, oils, drilling sprays. Water should be avoided, as it does not have the properties of lubricating fluids, but only cools.
Large diameter holes
To the question of how to drill a large diameter hole in metal, there is only one answer: V technological process reaming necks. For example, you need to increase the neck and get a size of thirty millimeters in diameter. First, it is drilled with a tool of a smaller diameter, for example, four millimeters, then under the size of 8 millimeters, then - 12 millimeters, and so each size expands to the result.
The neck of a large diameter in the product can be made on a lathe. The operation is as follows: drilling a hole, boring a neck right size. As pre-drilling is necessary, the process can be divided into stages: drilling of small diameter, reaming with a gradual increase in the diameter of the drill.
Drilling thin sheet
A feature of obtaining armholes in thin sheet metal is his reliable fastening. After the drill exits to the other side, there is a danger that the sheet may suddenly jam and break out if it was held in hands. the best way reliable fastening of the sheet is a clamp. In this case, the risk that the tin will be torn out is much less. The amount of burrs formed is reduced, which will greatly facilitate the finishing processing of the element.
If the metal is 0.1 mm thick, you can make a hole without a drill using a metal punch tool. Its design is very simple, like pliers. A punch is attached to one lever, a matrix to the other. The principle is the same as for cold firmware using a stamp.
To cut a through groove in sheet steel, it is necessary, according to size, to drill a successive row of holes, connecting them into a single slot with a chisel and a hammer. To do this, it is necessary to cut off the jumpers between the holes and clean the irregularities with a file.
metal pipes
In case of drilling metal pipe make sure that the workpiece is securely fixed in the vise. It is advisable to fix the drill on a vertical stand. Insert a piece of wood, identical in shape and size, into the pipe, which will save the pipe from deformation. In this case, apply a small feed.
Getting narrow nozzles
Drilling deep holes of small diameter can only be done on a special machine or a lathe using a fixture. The part is clamped in a 3-jaw chuck and checked for runout with a runout indicator. The device is attached to the tool holder. A drill chuck with a drill is installed in the fixture. First, the hole is centered, then the nozzle is drilled to a predetermined depth. Apply tailstock problematic, since the overthrown must be constantly withdrawn for the release of chips and lubrication.
To obtain vertical holes, a right-angle drilling fixture is used. For an electric drill, this vertical post at a 90 degree angle to the base. The easiest way is to use a vertical drilling machine.
The work of drilling holes in metal, depending on the type of holes and the properties of the metal, can be performed different instrument and using various methods. We want to tell you about drilling methods, tools, as well as safety precautions when performing these works.
Drilling holes in metal may be needed during repairs engineering systems, household appliances, car, creating structures from sheet and profile steel, designing crafts from aluminum and copper, in the manufacture of circuit boards for radio equipment, and in many other cases. It is important to understand what kind of tool is needed for each type of work so that the holes are the right diameter and in a strictly intended place, and what safety measures will help to avoid injury.
Tools, fixtures, drills
The main tools for drilling are hand and electric drills, as well as, if possible, drilling machines. The working body of these mechanisms - the drill - can have a different shape.
There are drills:
- spiral (most common);
- screw;
- crowns;
- conical;
- feathers, etc.
Drill production various designs standardized by numerous GOSTs. Drills up to Ø 2 mm are not marked, up to Ø 3 mm - the section and steel grade are indicated on the shank, larger diameters may contain additional information. To obtain a hole of a certain diameter, you need to take a drill a few tenths of a millimeter smaller. The better the drill is sharpened, the smaller the difference between these diameters.
Drills differ not only in diameter, but also in length - short, elongated and long are produced. important information is the ultimate hardness of the metal being processed. The shank of the drills can be cylindrical and conical, which should be borne in mind when selecting a drill chuck or adapter sleeve.
1. Drill with cylindrical shank. 2. Tapered shank drill. 3. Drill with a sword for carving. 4. Center drill. 5. Drill with two diameters. 6. Center drill. 7. Conical drill. 8. Conical multi-stage drill
For some work and materials, special sharpening is required. The harder the metal being processed, the sharper the edge must be sharpened. For thin sheet metal, a conventional twist drill may not be suitable, you will need a tool with a special sharpening. Detailed recommendations For various types drills and processed metals (thickness, hardness, hole type) are quite extensive, and in this article we will not consider them.
Various types of drill sharpening. 1. For hard steel. 2. For of stainless steel. 3. For copper and copper alloys. 4. For aluminum and aluminum alloys. 5. For cast iron. 6. Bakelite
1. Standard sharpening. 2. Free sharpening. 3. Diluted sharpening. 4. Heavy sharpening. 5. Separate sharpening
To fix parts before drilling, a vice, stops, conductors, corners, clamps with bolts and other devices are used. This is not only a safety requirement, it is actually more convenient, and the holes are of better quality.
To chamfer and process the surface of the channel, they use a countersink of a cylindrical or conical shape, and to mark a point for drilling and so that the drill does not “jump off” - a hammer and a center punch.
Advice! The best drills until now, they are considered to be issued in the USSR - exact adherence to GOST in geometry and metal composition. German Ruko with titanium coating are also good, as well as drills from Bosch - proven quality. Good feedback about Haisser products - powerful, usually with a large diameter. The Zubr drills, especially the Cobalt series, proved to be worthy.
Drilling modes
It is very important to correctly fix and guide the drill, as well as select the cutting mode.
When making holes in metal by drilling important factors are the number of revolutions of the drill and the feed force applied to the drill, directed along its axis, providing the penetration of the drill at one revolution (mm / rev). When working with different metals and drills, different cutting conditions are recommended, and the harder the metal being processed and the larger the diameter of the drill, the lower the recommended cutting speed. Index correct mode— beautiful, long shavings.
Use the tables to choose the right mode and not dull the drill prematurely.
| Feed S 0 , mm/rev | Drill diameter D, mm | |||||||||
| 2,5 | 4 | 6 | 8 | 10 | 12 | 146 | 20 | 25 | 32 | |
| Cutting speed v, m/min | ||||||||||
| When drilling steel | ||||||||||
| 0,06 | 17 | 22 | 26 | 30 | 33 | 42 | — | — | — | — |
| 0,10 | — | 17 | 20 | 23 | 26 | 28 | 32 | 38 | 40 | 44 |
| 0,15 | — | — | 18 | 20 | 22 | 24 | 27 | 30 | 33 | 35 |
| 0,20 | — | — | 15 | 17 | 18 | 20 | 23 | 25 | 27 | 30 |
| 0,30 | — | — | — | 14 | 16 | 17 | 19 | 21 | 23 | 25 |
| 0,40 | — | — | — | — | — | 14 | 16 | 18 | 19 | 21 |
| 0,60 | — | — | — | — | — | — | — | 14 | 15 | 11 |
| When drilling cast iron | ||||||||||
| 0,06 | 18 | 22 | 25 | 27 | 29 | 30 | 32 | 33 | 34 | 35 |
| 0,10 | — | 18 | 20 | 22 | 23 | 24 | 26 | 27 | 28 | 30 |
| 0,15 | — | 15 | 17 | 18 | 19 | 20 | 22 | 23 | 25 | 26 |
| 0,20 | — | — | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 |
| 0,30 | — | — | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 19 |
| 0,40 | — | — | — | — | 14 | 14 | 15 | 16 | 16 | 17 |
| 0,60 | — | — | — | — | — | — | 13 | 14 | 15 | 15 |
| 0,80 | — | — | — | — | — | — | — | — | — | 13 |
| When drilling aluminum alloys | ||||||||||
| 0,06 | 75 | — | — | — | — | — | — | — | — | — |
| 0,10 | 53 | 70 | 81 | 92 | 100 | — | — | — | — | — |
| 0,15 | 39 | 53 | 62 | 69 | 75 | 81 | 90 | — | — | — |
| 0,20 | — | 43 | 50 | 56 | 62 | 67 | 74 | 82 | - | - |
| 0,30 | — | — | 42 | 48 | 52 | 56 | 62 | 68 | 75 | — |
| 0,40 | — | — | — | 40 | 45 | 48 | 53 | 59 | 64 | 69 |
| 0,60 | — | — | — | — | 37 | 39 | 44 | 48 | 52 | 56 |
| 0,80 | — | — | — | — | — | — | 38 | 42 | 46 | 54 |
| 1,00 | — | — | — | — | — | — | — | — | — | 42 |
Table 2. Correction factors
Table 3. Revolutions and feeds for various drill diameters and drilling in carbon steel
Types of holes in metal and methods for drilling them
Types of holes:
- deaf;
- through;
- half (incomplete);
- deep;
- large diameter;
- for internal thread.
Threaded holes require the determination of diameters with tolerances established in GOST 16093-2004. For common hardware, the calculation is given in table 5.
Table 5. The ratio of metric and inch threads, as well as the selection of the hole size for drilling
| Metric thread | Inch thread | Pipe thread | |||||||
| Thread diameter | Thread pitch, mm | Thread hole diameter | Thread diameter | Thread pitch, mm | Thread hole diameter | Thread diameter | Thread hole diameter | ||
| min. | Max. | min. | Max. | ||||||
| M1 | 0,25 | 0,75 | 0,8 | 3/16 | 1,058 | 3,6 | 3,7 | 1/8 | 8,8 |
| M1.4 | 0,3 | 1,1 | 1,15 | 1/4 | 1,270 | 5,0 | 5,1 | 1/4 | 11,7 |
| M1.7 | 0,35 | 1,3 | 1,4 | 5/16 | 1,411 | 6,4 | 6,5 | 3/8 | 15,2 |
| M2 | 0,4 | 1,5 | 1,6 | 3/8 | 1,588 | 7,7 | 7,9 | 1/2 | 18,6 |
| M2.6 | 0,4 | 2,1 | 2,2 | 7/16 | 1,814 | 9,1 | 9,25 | 3/4 | 24,3 |
| M3 | 0,5 | 2,4 | 2,5 | 1/2 | 2,117 | 10,25 | 10,5 | 1 | 30,5 |
| M3.5 | 0,6 | 2,8 | 2,9 | 9/16 | 2,117 | 11,75 | 12,0 | — | — |
| M4 | 0,7 | 3,2 | 3,4 | 5/8 | 2,309 | 13,25 | 13,5 | 11/4 | 39,2 |
| M5 | 0,8 | 4,1 | 4,2 | 3/4 | 2,540 | 16,25 | 16,5 | 13/8 | 41,6 |
| M6 | 1,0 | 4,8 | 5,0 | 7/8 | 2,822 | 19,00 | 19,25 | 11/2 | 45,1 |
| M8 | 1,25 | 6,5 | 6,7 | 1 | 3,175 | 21,75 | 22,0 | — | — |
| M10 | 1,5 | 8,2 | 8,4 | 11/8 | 3,629 | 24,5 | 24,75 | — | — |
| M12 | 1,75 | 9,9 | 10,0 | 11/4 | 3,629 | 27,5 | 27,75 | — | — |
| M14 | 2,0 | 11,5 | 11,75 | 13/8 | 4,233 | 30,5 | 30,5 | — | — |
| M16 | 2,0 | 13,5 | 13,75 | — | — | — | — | — | — |
| M18 | 2,5 | 15,0 | 15,25 | 11/2 | 4,333 | 33,0 | 33,5 | — | — |
| M20 | 2,5 | 17,0 | 17,25 | 15/8 | 6,080 | 35,0 | 35,5 | — | — |
| M22 | 2,6 | 19,0 | 19,25 | 13/4 | 5,080 | 33,5 | 39,0 | — | — |
| M24 | 3,0 | 20,5 | 20,75 | 17/8 | 5,644 | 41,0 | 41,5 | — | — |
through holes
Through holes penetrate the workpiece completely, forming a passage in it. A feature of the process is the protection of the surface of the workbench or tabletop from the exit of the drill beyond the workpiece, which can damage the drill itself, as well as provide the workpiece with a “burr” - a hart. To avoid this, use the following methods:
- use a workbench with a hole;
- put a gasket made of wood or a “sandwich” under the part - wood + metal + wood;
- put a metal bar under the part with a hole for the free passage of the drill;
- reduce the feed rate at the last stage.
The latter method is mandatory when drilling holes "in place" so as not to damage closely spaced surfaces or parts.
Holes in thin sheet metal are cut with spatula drills, because the twist drill will damage the edges of the workpiece.
blind holes
Such holes are made to a certain depth and do not penetrate the workpiece through and through. There are two ways to measure depth:
- limiting the length of the drill with a sleeve stop;
- limiting the length of the drill with an adjustable stop chuck;
- using a ruler fixed on the machine;
- a combination of methods.
Some machines are equipped with an automatic feed to a given depth, after which the mechanism stops. During the drilling process, it may be necessary to stop the work several times to remove the chips.
Holes of complex shape
Holes located on the edge of the workpiece (half) can be made by connecting two workpieces or a workpiece and a gasket with faces and clamping with a vise and drilling a full hole. The gasket must be made of the same material as the workpiece being processed, otherwise the drill will “leave” in the direction of least resistance.
A through hole in the corner (shaped rolled metal) is performed by fixing the workpiece in a vice and using a wooden gasket.
It is more difficult to drill a cylindrical workpiece tangentially. The process is divided into two operations: preparation of a platform perpendicular to the hole (milling, countersinking) and drilling itself. Drilling holes in surfaces located at an angle also begins with the preparation of the site, after which a wooden gasket is inserted between the planes, forming a triangle, and a hole is drilled through the corner.
Hollow parts are drilled, filling the cavity with a cork made of wood.
Stepped holes are produced using two techniques:
- Reaming. The hole is drilled to the full depth with a drill of the smallest diameter, after which it is drilled to a given depth with drills with diameters from smaller to larger. The advantage of the method is a well-centered hole.
- Reducing the diameter. A hole of maximum diameter is drilled to a given depth, then the drills are changed with a successive decrease in diameter and a hole deepening. With this method, it is easier to control the depth of each step.
1. Drilling a hole. 2. Diameter reduction
Large diameter holes, annular drilling
Obtaining holes of large diameter in massive workpieces, up to 5-6 mm thick, is a laborious and costly business. Relatively small diameters - up to 30 mm (maximum 40 mm) can be obtained using cone, and preferably step-cone drills. For holes with a larger diameter (up to 100 mm), hollow bi-metal hole saws or hole saws with carbide teeth with a center drill will be required. Moreover, the craftsmen traditionally recommend Bosch in this case, especially on hard metal, such as steel.
Such annular drilling less energy-intensive, but may be more costly financially. In addition to drills, the power of the drill and the ability to work at the lowest speeds are important. Moreover, the thicker the metal, the more you want to make a hole on the machine, and when in large numbers holes in a sheet with a thickness of more than 12 mm, it is better to immediately look for such an opportunity.
In a thin-sheet blank, a large-diameter hole is obtained using narrow-toothed crowns or a milling cutter mounted on a grinder, but the edges in the latter case leave much to be desired.
Deep holes, coolant
Sometimes a deep hole is required. In theory, this is such a hole, the length of which is five times larger diameter. In practice, deep drilling is called, requiring forced periodic removal of chips and the use of coolants (cutting fluids).
In drilling, coolants are needed primarily to reduce the temperature of the drill and workpiece, which are heated by friction. Therefore, when making holes in copper, which has a high thermal conductivity and is itself capable of removing heat, coolant can be omitted. Cast iron is drilled relatively easily and without lubrication (except for high-strength ones).
In production, industrial oils, synthetic emulsions, emulsols and some hydrocarbons are used as coolants. In home workshops you can use:
- technical vaseline, castor oil - for mild steels;
- laundry soap— for aluminum alloys of D16T type;
- a mixture of kerosene with castor oil - for duralumin;
- soapy water - for aluminum;
- turpentine diluted with alcohol - for silumin.
The universal coolant can be prepared independently. To do this, you need to dissolve 200 g of soap in a bucket of water, add 5 tablespoons of machine oil, you can use it, and boil the solution until a soapy homogeneous emulsion is obtained. Some masters use lard to reduce friction.
| Processed material | Coolant |
| Steel: | |
| carbonaceous | Emulsion. Sulfurized oil |
| structural | Sulfurized oil with kerosene |
| instrumental | Blended oils |
| alloyed | Blended oils |
| Ductile iron | 3-5% emulsion |
| Cast iron | Without cooling. 3-5% emulsion. Kerosene |
| Bronze | Without cooling. Blended oils |
| Zinc | Emulsion |
| Brass | Without cooling. 3-5% emulsion |
| Copper | Emulsion. Blended oils |
| Nickel | Emulsion |
| Aluminum and its alloys | Without cooling. Emulsion. Mixed oils. Kerosene |
| Stainless, high temperature alloys | Mixture of 50% sulfurated oil, 30% kerosene, 20% oleic acid (or 80% sulfofresol and 20% oleic acid) |
| Fiber, vinyl plastic, plexiglass and so on | 3-5% emulsion |
| Textolite, getinaks | Compressed air blowing |
Deep holes can be made by solid and annular drilling, and in the latter case, the central rod formed by the rotation of the crown is broken out not entirely, but in parts, weakening it with additional holes of small diameter.
Solid drilling is performed in a well-fixed workpiece twist drill, into the channels of which coolant is supplied. Periodically, without stopping the rotation of the drill, it is necessary to remove it and clean the cavity from chips. The work with a twist drill is carried out in stages: first, a short hole is taken and a hole is drilled, which is then deepened with a drill of the appropriate size. With a significant depth of the hole, it is advisable to use guide bushings.
With regular drilling of deep holes, it can be recommended to purchase a special machine with automatic feeding Coolant to the drill and precise centering.
Drilling by marking, template and jig
You can drill holes according to the markings made or without it - using a template or a jig.
Marking is done with a punch. A hammer blow marks a place for the tip of the drill. A felt-tip pen can also mark a place, but a hole is also needed so that the tip does not move from the intended point. The work is carried out in two stages: preliminary drilling, hole control, final drilling. If the drill "left" from the intended center, notches (grooves) are made with a narrow chisel that guide the tip to a given place.
To determine the center of a cylindrical workpiece, a square piece of tin is used, bent at 90 ° so that the height of one shoulder is approximately one radius. Applying a corner from different sides of the workpiece, draw a pencil along the edge. As a result, you have an area around the center. You can find the center by the theorem - the intersection of perpendiculars from two chords.
A template is needed when making a series of parts of the same type with several holes. It is convenient to use it for a pack of thin-sheet blanks connected with a clamp. This way you can get several drilled blanks at the same time. Instead of a template, a drawing or diagram is sometimes used, for example, in the manufacture of parts for radio equipment.
The conductor is used when the accuracy of maintaining the distances between the holes and the strict perpendicularity of the channel are very important. When drilling deep holes or when working with thin-walled tubes, in addition to the conductor, guides can be used to fix the position of the drill relative to the metal surface.
When working with a power tool, it is important to remember human safety and prevent premature wear of the tool and possible marriage. For this reason, we have collected some helpful tips:
- Before work, you need to check the fastening of all elements.
- Clothing when working on a machine or with an electric drill should not be with elements that can fall under the action of rotating parts. Protect your eyes from chips with goggles.
- The drill, when approaching the surface of the metal, must already rotate, otherwise it will quickly become dull.
- It is necessary to remove the drill from the hole without turning off the drill, reducing the speed if possible.
- If the drill does not go deep into the metal, then its hardness is lower than that of the workpiece. Increased hardness in steel can be detected by running a file over the sample - the absence of traces indicates increased hardness. In this case, the drill must be selected from a carbide with additives and work at low speeds with a small feed.
- If a small diameter drill does not fit well in the chuck, wind a few turns of brass wire around its shank, increasing the gripping diameter.
- If the surface of the workpiece is polished, put a felt washer on the drill to ensure that it does not scratch even when it comes into contact with the drill chuck. When fastening workpieces made of polished or chrome-plated steel, use spacers made of fabric or leather.
- When making deep holes, a rectangular piece of foam placed on a drill can serve as a measuring instrument and at the same time blow off small chips while rotating.
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, lamp or piping. That is, to carry out this not in the conditions of a workshop or workshop, but directly on the spot. The easiest way to drill in such conditions is to use an electric drill. But, imagine how much pressure you need to apply to it in order to drill a hole with a diameter of 16 or 20 mm? The question is not rhetorical - the effort will be about 40-50 kgf. This is not at all easy to ensure if the intended hole is located above the shoulder level of the driller. Even 10 years ago, when such a task arose, even professionals resorted to 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 according to 11 grades.
However, many are sure that core drilling is a rather expensive method, economically viable only with industrial volumes. Is such a statement true? Partly. To date, you can choose from several options for tools and equipment for drilling holes in metal of large diameter without reaming. At the same time, the cost per hole will be justified even when drilling only a few holes.
Consider, what tool options for drilling through holes of large diameter in metal does the market offer. For comparison, we take a diameter of 51 mm.
First, this bimetallic crowns. The choice includes samples from the cheapest, which are immediately sold in sets and cannot be accepted by us in this review for the reason that their purpose is to drill wood, and if they manage to drill a sheet of metal, it will be no thicker than 0.5 mm . At a price of 240 rubles, products with a wall thickness of 1-1.2 mm start, often it is labeled 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, cobalt is probably not there at all. twice as expensive crowns of more decent quality, really allowing you to drill stainless steel and ordinary steel a few millimeters thick. Bimetal crowns this level allows you to drill 5-20 holes in a steel sheet with a thickness of 5 mm. At the same time, the use of any lubricating-cooling composition ensures the achievement top bar this range. At the third stage there are bimetallic crowns of world famous brands, which are twice as expensive, can be equipped with special devices for a quick change in a drill, but the resource is not much or does not exceed the average price level at all.
Drilling holes of large diameter in steel sheets with a thickness of more than 5-6 mm for bi-metal crowns is a great difficulty, although sometimes you can hear a different opinion. It is based on data on the total drilling depth of such crowns - 35-38 mm. As a rule, only sellers of bimetallic crowns, who have no more worthy tool, risk advising to drill a 30 mm sheet or beam in this way. The fact is that the bimetallic crown is devoid of a chip removal groove, and as soon as the thickness of the drilled metal becomes greater than the height of the tooth of the crown, problems with chip removal begin. In addition, the body of the bimetal bit is not quite cylindrical shape, this causes jamming in the metal of solid thickness.
Unlike bimetallic crowns, they provide more accurate drilling. Carbide body hole saw- turned, while the bimetallic crown is rolled from a 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 attachment, we will analyze only the cutting part. The most expensive part of the crown is the carbide teeth. The quality of the material greatly affects the drilling speed, impact resistance, bit life and the ability to drill alloyed steels with high content chrome.
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-removing groove, and they will not be able to drill 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, fakes are not common at present, and almost all samples found on the market are of acceptable quality, but excellent quality 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 provides soft cutting, no vibration, reduced load on the cutting edges and, as a result, an increase in the resource of the crown. In such crowns, there is a short or long chip removal groove, 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. 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 terms 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, to consider 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, investments will amount to 21,164 rubles without 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 causes a high cost of investing in equipment, and together with a crown it will be about 56,000 rubles, or, alternatively, with magnetic drill stand and a separately purchased drill about 50,000. Drilling such holes with a drill from your hands 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 bi-metal and carbide drill bits. The choice of tool is made depending on the required accuracy. When drilling holes with a bimetallic crown, the ovality of the holes and the increase in diameter from the desired one can reach 4% or in absolute terms - 2 - 3 mm. When drilling with a carbide crown - only 0.6 - 1 mm. In addition, all the carbide drill bits presented in the review, and almost all drill bits for metal available on the market, also drill stainless steel.
