How to make a big hole in metal. What and how to drill deep and large holes in metal parts

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 when repairing 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 tool is needed for each type of work so that the holes are obtained desired diameter and in a strictly designated place, and what safety measures will help to avoid injuries.

Tools, fixtures, drills

The main tools for drilling are hand 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.

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, large 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 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 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 feedback about Haisser products - powerful, as a rule, 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 various metals and drills, it is recommended various modes cutting, and the harder the metal being processed and the more drill diameter a, 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
		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 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:

1. 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.
2. 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 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 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 (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 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, 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 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 deep holes you can recommend the purchase 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. In this regard, we have collected some useful tips:

1. Before work, you need to check the fastening of all elements.
2. 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.
3. The drill, when approaching the surface of the metal, must already rotate, otherwise it will quickly become dull.
4. It is necessary to remove the drill from the hole without turning off the drill, reducing the speed if possible.
5. 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.
6. If a small diameter drill does not fit well in the chuck, wind a few turns of brass wire around its shank, increasing the diameter to grip.
7. 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.
8. 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.

Why do some people drill metal quickly and without much difficulty, while others resemble an epic, accompanied by broken and blunt drills?

Drill selection

Drilling of metal parts is usually performed using twist drills with two cutting edges in the working part and two helical grooves for chip removal.

The most common are drills made of R6M5 steel, drills with cobalt in the marking have the letter K (R6M5K5), such a tool blunts more slowly, but also costs more.

More high performance drills with titanium coating have strength. They differ from the rest of the tool with a yellow coating.

In addition, there are also stepped ones, which have the appearance of a Christmas tree in a longitudinal section. Made of high speed steel, they have a pitch of 2 mm, which allows them to make holes with a diameter of 4 to 36 mm in sheet metal.

Lubrication and cooling

In the process of drilling metal, the drill under the influence of friction forces can become very hot. Due to overheating, the hardness of the drill decreases and it loses its cutting properties.

This can be avoided both by cooling the drill and by reducing the friction force. For simultaneous lubrication and cooling of the drill, there are special cutting fluids and pasty formulations.

Before starting work, liquid lubricant is applied to the drill with a brush or injected with an oil can into the hole to be drilled, the paste is applied to the drill immediately before drilling.

At home in the absence special means machine oil can be used for lubrication and cooling; ordinary gray cast iron is drilled dry.

Drilling technology

Before starting, be sure to make a small indentation in the center of the future hole with a core and a hammer. This will avoid going to the side of the drill at the initial stage of its cutting into the metal.

Under the metal blank, place a piece of board of the appropriate size. The part will slip less and the exit hole edges will be much cleaner.

Hold the drill so that the drill is exactly perpendicular to the plane of the workpiece. Otherwise, the drill will deviate from the intended axis, and the thin one may even break. The use of a special drilling stand, spacer or guide greatly facilitates the work.

On the initial stage drilling, pressing the drill should be barely perceptible. As the drill cuts into the metal, the pressure can be slightly increased.

The indicator of the correctness of the choice of force for pressing is the chips issued by the drill. Small crumbs indicate that the pressure needs to be increased, thin chips indicate normal feed, while thick spiral chips indicate the need to reduce the force on the drill.

Beginning masters make the most mistakes when choosing the speed of drilling metal, setting the drill rotation speed too high. As a result, the drill overheats, quickly becomes dull and becomes unusable.

When drilling metal with a drill with a diameter of 3-4 mm, its rotation speed should not exceed 1000 rpm. With an increase in the diameter of the drill, the speed of the drill should decrease proportionally, reaching 400 rpm for drills with a thickness of 13 mm or more.

When making a through hole, pay special attention to the final phase of drilling. The drill can catch on the side cutters with a burr formed at the exit of the hole, which is fraught with a sudden blockage of the drill or even its fracture.

Always follow the completion of the drilling process by reducing the pressure on the tool.

If you need to make a hole with a large diameter, first pre-drill using a drill with a diameter of 3 to 5 mm. Then drill it with an 8 mm drill and only after that screw a drill of the desired diameter in the chuck of an electric drill.

This approach will provide more efficient and faster cutting of metal, reducing the likelihood of misalignment.

Good luck to you! May you succeed!

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 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 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 correct position, as well as provide 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. 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 metal products needs to be done with refrigeration. 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 metal is one of the most common plumbing operations. Collapsible and non-collapsible connections - rivet, screw, bolt, hairpin - require holes. To drill metal, it is enough to have a drill, a drill of the appropriate diameter and a center punch with a hammer for basting the hole.

Drill selection

If holes in the metal are drilled for threading, then according to GOST 24705-81, for the most commonly used thread sizes (for standard large pitches): M4, M5, M6, M8, M10 and M12 - the diameter of the drills will be 3.3, respectively; 4.2; 5; 6.7; 8.4; 10.2 mm. It is quite acceptable if drilling for threading will be carried out with a drill, the diameter of which differs slightly (by 0.1 mm) from the GOST dimensions in one direction or another.

When purchasing drills, you need to keep in mind that conventional drills made of high-speed tool steel (for example, R6M5) are designed for drilling metals that do not have high hardness. To drill through hard metal, carbide drills are required. These drills can be full carbide or have only a carbide tip.

Sometimes, before starting drilling, it is not known what hardness the metal is to be drilled. Therefore, when you see at the first moment of drilling that the drill does not penetrate into the metal, you must immediately stop drilling, otherwise the drill will be irrevocably disabled, overheating and losing hardness. Evidence of this will be the appearance of a dark blue color on it. Before drilling metal, the hardness of which is not known, you can run a file through it. If the latter does not leave traces on the metal, then the material has increased hardness.

How to drill metal

Optimal for drilling most metals are low and medium speeds - 500-1000 rpm. High speeds quickly heat up the drill, as a result of which its annealing and softening can occur. When drilling, do not press too hard on the drill, the feed should be slow and smooth.

When drilling metal, the sharpness of the drill is very important, while the drill becomes dull very quickly. The rate of blunting of the drill depends in particular on revolutions, feed force, cooling and other factors, however, no matter how hard you try, if a non-aluminum alloy is being drilled, the drill's operating time to unsatisfactory performance is measured in minutes.

Before drilling, it is necessary to mark the hole by punching it. To do this, you need to install the tip of the center punch (or dowel) in the intended center of the hole and hit it with a hammer. Piercing is necessary to prevent slipping of the drill at the first moment of drilling. If the core mark is not large enough to hold a large diameter drill, then first widen the hole with a small diameter drill.

For creating better conditions drilling, it is advisable to dip the tip of the drill into machine oil or drop it into the place of punching. The oil in the drilling zone contributes to better cooling of the drill and facilitates metal cutting. A drill drilled with oil is less blunt, requires less sharpening, and lasts longer. A special emulsion, soapy water, kerosene are also used as a coolant. According to some craftsmen, lard is a good lubricant and coolant. Before drilling, a rotating drill is immersed in a piece of fat, which melts during drilling and has a lubricating and cooling effect. But still the simplest and most convenient remedy is soapy water. It does not stain, and there is soap in every home. It is enough to drop it once at the beginning of drilling and in the process. You can periodically dip the drill in a soapy solution.

When through drilling with a high feed, a burr (burr) is formed at the exit of the hole, for which the drill clings to its side cutters. As a result, a sharp blocking of the drill and its fracture or chipping off of the cutter can occur, and even at this moment the drill becomes especially intensely blunt. Such stops also have a negative effect on the state of the drill. To avoid the formation of burrs, you need to finish drilling holes in metal with a low feed. It is also advisable to place a wooden block under the drilled part, which prevents the formation of a burr. The bar and the workpiece must be tightly pressed against each other. For greater effect, you can put not a wooden block, but a plate of the same or less solid metal, which should be firmly pressed against the exit point of the drill.

Most often, it is necessary to drill steel, but it is often necessary to drill other metals, which have their own drilling characteristics. Aluminum, for example, envelops the drill, making it difficult for it to penetrate deep and widening the resulting hole. If you want to drill a precise hole in aluminum (for example, for a thread), you must always apply coolant and remove the drill from the hole more often to clean it. Ordinary gray cast iron is relatively easy to drill and does not require coolant or lubrication. But drilling in cast iron can bring surprises. There are ductile gray cast irons that need to be drilled with a carbide drill bit. White cast iron, the main structural component of which is cementite, is very hard, it requires a high-strength drill.

Large diameter holes should be drilled in stages. First you need to drill the part with a thin drill, then drill the hole to a larger diameter. For example, a hole with a diameter of 12 mm is best drilled in two or three steps - sequentially with 5, 10 and 12 mm drills.

Blunt drills need to be sharpened in a timely manner. It is better to do this with a sharpening tool, but you can do without it. In this case, you need to pay attention to the symmetry of the tip of the drill. If the sharpened edges do not meet strictly in the center, the hole drilled with such a drill will have a larger diameter, since one cutting edge will be longer than the other. The standard point angle (the angle between the cutting edges) is 118°. For drilling aluminum, an angle of 130-140 ° is considered optimal, soft bronze and red copper 125-130 °. However, all these metals can be drilled with a standard angle drill. Read more about drill sharpening.

When drilling, it is necessary to maintain the verticality of the drill relative to the metal surface (if it is not required to drill an inclined hole). When making holes in thin sheets this requirement is not as relevant as for thick-walled or hollow parts. Drilling pipes, for example, often leads to the fact that the inlet and outlet holes are offset relative to each other - the more, the larger the diameter of the pipe. It is quite difficult to maintain the perpendicularity of the drill by eye, so you can use home-made or purchased drilling jigs or guides that ensure the perpendicularity of the drill.

Conductors are also needed for drilling two or more holes in mating parts. The best way ensuring that the holes match is drilling them as an assembly. When drilling rivet holes, complete drilling is a must. Having drilled the first hole, you can use it to connect the parts with a bolt so that you can drill the remaining holes without fear that the parts will move relative to each other. If it is impossible or inconvenient to drill mating assembly parts, then a jig or guide must be used. You should know that no matter how accurately the mating holes are marked and punched, they will still not match absolutely exactly, since when drilling even a punched hole, the drill will go a little to the side.

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