What and how to drill deep and large holes in metal parts. How to drill hardened steel at home How to make holes in metal

The work of drilling holes in metal, depending on the type of holes and the properties of the metal, can be performed with different tools and using different techniques. 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 when repairing engineering systems, household appliances, cars, 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 manual and electric drills, and, 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.

The production of drills of various designs is 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 a 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 of drills and processed metals (thickness, hardness, hole type) are quite extensive, and we will not consider them in this article.

Various types of drill sharpening. 1. For hard steel. 2. For 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 are still considered to be those produced 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 reviews about Haisser products are powerful, as a rule, 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. An indicator of the correct mode is a beautiful, long chip.

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
Thread diameter	Thread pitch, mm	min.	Max.	Thread diameter	Thread pitch, mm	min.	Max.	Thread diameter	Thread hole diameter
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 angled surfaces also begins with site preparation, after which a wooden spacer 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 is less energy-intensive, but may be more financially costly. 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 with a large number of 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 a hole whose length is five times the diameter. In practice, deep drilling is called, requiring forced periodic removal of chips and the use of coolants (coolants).

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 the 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, 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 with a twist drill, through 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 coolant supply 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. In this regard, we have collected some useful 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.

Drills for metal are selected based on the diameters of the holes and the properties of the material being processed. As a rule, they are made of 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. Power tool manufacturers indicate the relevant technical data 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 to each other by means of bolts, studs, pins and rivets. If the hole is drilled for the purpose of threading, you should pay special attention to the choice of drill diameter. Due to its beating in the cartridge, a breakdown of the hole occurs, which must be taken into account. Indicative data are presented in the table.

To reduce breakdown, drilling is performed in two stages: first with a smaller diameter drill, and then with the main one. The same method of sequential reaming is used when it is necessary to make a hole of a large diameter.

How to drill metal with a drill

The peculiarity of drilling metal with a drill is that it is necessary to manually hold the tool, give it the correct position, and also ensure the required cutting speed.

After marking the workpiece, the center of the future hole should be punched. This will prevent the drill from moving away from the set point. For the convenience of work, the workpiece should be clamped in a bench vise or placed on a stand so that it takes a stable position. The drill is set strictly perpendicular to the surface to be drilled. This is important to avoid damage.

When drilling metal, the drill does not need to exert much pressure. On the contrary, it should decrease as you go. This will prevent breakage of the drill and also reduce burr formation on the trailing edge of the through hole. Chip removal should be monitored. If the cutting tool jams, it is released by reverse rotation.

Cutting mode selection

When using a tool made of high speed steel, you can refer to the speed according to the data in the table. When working with carbide drills, the allowable values are 1.5 ... 2 times higher.

Drilling of metal products must be carried out 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 surface of the hole in this case will be quite low. An emulsion is usually used as a coolant for hard steels. At home, machine oil is suitable. Cast iron and non-ferrous metals can be drilled without coolant.

Features of deep hole drilling

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 helical grooves, through which chips are removed, and liquid is also supplied for cooling and lubrication.

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 that, 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.

Drilling through holes in metal blanks is carried out with various tools using special techniques. Many specialists in the performance of engineering work have to drill holes in metal structures quite 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 are electric 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, preliminary preparation for the process is extremely important. 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. They are carried out to the required depth, without penetrating the product 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 are equipped with automatic feed systems for a given depth of penetration, 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 forcefully provide cooling measures for the drill and the workpiece 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, cone, crown-shaped or stepped drills are used. 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 for internal threads. The technology has to be divided into two steps: preliminary site preparation 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.
The drill should exit the drilled hole gradually, reducing the 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 no roughness remains on the grade, a diamond-tipped drill or a harder material should be selected and drilled at low RPM.
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. Manufacturers of electric tools mark devices, indicating the technical characteristics 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 ourselves and select the appropriate tool, of which we have a large selection. As a result, you will get the perfect solution in a short time.

The work of drilling holes in metal, depending on the type of holes and the properties of the metal, can be performed with different tools and using different techniques.

We want to tell you about drilling methods, tools, as well as safety precautions when performing these works.

Tools, fixtures, drills

The main tools for drilling are manual and electric drills, and, if possible, drilling machines. The working body of these mechanisms - a drill - can have a different shape.

There are drills:

spiral (most common);
screw;
crowns;
conical;
feathers, etc.

Various types of drill sharpening. 1. For hard steel. 2. For 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

Advice! The best drills are still considered to be those produced 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 reviews about Haisser products - powerful, as a rule, 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.

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
Thread diameter	Thread pitch, mm	min.	Max.	Thread diameter	Thread pitch, mm	min.	Max.	Thread diameter	Thread hole diameter
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

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.

Holes of complex shape

A through hole in the corner (shaped rolled metal) is performed by fixing the workpiece in a vice and using a wooden gasket.

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 task. 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.

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

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 the D16T type;
a mixture of kerosene with castor oil - for duralumin;
soapy water - for aluminum;
turpentine diluted with alcohol - for silumin.

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

With regular drilling of deep holes, it can be recommended to purchase a special machine with automatic coolant supply 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.

When working with a power tool, it is important to remember human safety and prevent premature wear of the tool and possible marriage. In this regard, we have collected some useful 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 the building structure or hang a shelf, lamp or pipeline. 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 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 wood, and if they manage to drill a sheet of metal, then 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 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, 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 that the upper bar of this range is reached. At the third stage there are bimetallic crowns of world-famous brands, which are twice as expensive, can be equipped with special devices for quick change in a drill, but do not exceed the average price level by much or 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 do not have a more worthy tool in their assortment, 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 bimetallic crown is not quite cylindrical, which causes jamming in the metal of solid thickness.

Unlike bimetallic crowns, they provide more accurate drilling. The body of the carbide hole saw is chiselled, while the bi-metal hole saw is rolled from a band 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 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-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 is clearly required. 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.

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