Hi all! You can write a very long article about how to drill metal with a drill if you wish. But I see two main problems here:
- inability to drill accurately in the place where the hole is required
- rapid dulling of drills
Typically, inexperienced users encounter such problems. Experienced men know what to do in such cases. Well, considering myself an experienced person, I will take the liberty of telling you how to cope with these problems. Well, I’ll also give you some tips that will also come in handy.
How to drill in the right place?
If you think about this question a little, the answer should come to your mind even without a hint. Well, at least it seems so to me. But if you don’t want to think, then read.
For this case you will need a core. This is a tool made of durable steel, having cylindrical shape and a point at the end. 
We place the tip at the desired drilling location and hit the roll on the other side with a hammer several times.
Now that you have finished drilling, place a drill on the surface of the roughness and start drilling - the tip will not run away anywhere.
How to avoid dulling drills?
Metal drills become dull if they get too hot during operation, causing them to lose their strength. Heating occurs due to friction. Moreover, the faster it spins, the more it heats up.
Hence the obvious rule - you need to drill at low drill speeds. They should be no more than 1000 per minute. But who will measure this during work? So just don't press the start button all the way. The correct speed can be assessed as follows: the eye should see the rotation of the drill. That is, the grooves on it should not merge into one for vision.
When working with thick workpieces, additional cooling is necessary. It is provided by special lubricants or pastes that are added to the drilling site, or the drill is dipped into them. In addition, they not only cool, but also lubricate the tip, resulting in less friction.
IN living conditions There is no need to have special lubricants and pastes. You can get by with regular machine oil.
So, use a core, drill low and add some lube or oil and this job will be a cakewalk.
Well, a few more tips on this topic.
Drill types
For drilling, use only metal drills (not wood, for example). They have their own sharpening and are made from certain types become. The most common ones are marked P6M5 - these are high speed steel, which foreign manufacturers label as HSS.
To provide additional strength, the above drill bits are coated with titanium nitride. That's why they are yellow.
There are also stronger P18, which are used respectively for hard steels.
Also, to increase strength, cobalt can be added, and then the marking P6M5K5 is obtained.
Well, the most durable ones are drills with carbide tips. They are used for drilling alloy steels. It will also take ordinary steel, but buying it just for this will be somewhat savvy, since the price for them is quite high, and although it is hard, it still dulls. But it will be difficult to sharpen it later, since this requires diamond blade, which is also not very cheap, and you can’t buy it everywhere.
Drilling thick workpieces
If the workpiece has a thickness of more than 5 mm, and you need a hole larger than 8 mm, then it is better to make a hole first thin drill, and only then work fat.
Working with some types of metal
- When drilling into thick aluminum pieces, chips often clog the drill channels, making it more difficult to rotate. Therefore, when working with such material, remove the drill from the recess more often and remove the chips. Well, don’t forget to pour plenty of oil on it.
- If you need to drill black cast iron, then you do not need to add any lubricating and cooling substances, since it drills very well even dry
- Unlike black cast iron, white cast iron has increased strength, which means its processing will require durable drills and lubrication
These are the basic rules for drilling metal with a drill. I hope I was able to bridge this gap in your knowledge. Good luck with your homework and see you soon!
The work of drilling holes in metal, depending on the type of holes and the properties of the metal, can be performed different instruments and using various techniques. We want to tell you about drilling methods, tools, as well as safety precautions when performing this work.
Drilling holes in metal may be necessary for 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 tool is needed for each type of work so that the holes are made required diameter and in a strictly designated place, and what safety measures will help avoid injuries.
Tools, fixtures, drills
The main tools for drilling are hand and electric drills, and also, if possible, drilling machines. The working part of these mechanisms - the drill - can have different shapes.
Drills are distinguished:
- 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 also the ultimate hardness of the metal being processed. The drill shank can be cylindrical or conical, which should be kept in mind when selecting a drill chuck or adapter sleeve.
1. Drill with a cylindrical shank. 2. Drill with tapered shank. 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
Some jobs and materials require special sharpening. The harder the metal being processed, the sharper the edge should be sharpened. For thin sheet metal, a regular 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, type of hole) are quite extensive, and we will not consider them in this article.
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 secure parts before drilling, vices, stops, jigs, angles, 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, a cylindrical or conical countersink is used, and to mark the point for drilling and so that the drill does not “jump off,” a hammer and a center punch are used.
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, usually large diameter. The Zubr drills, especially the Cobalt series, performed well.
Drilling modes
It is very important to correctly secure 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, ensuring the depth of the drill with one revolution (mm/rev). When working with various metals and drills are recommended various modes cutting, 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 beautiful, long chips.
Use the tables to choose the right mode and avoid dulling 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 feed for different drill diameters and drilling carbon steel
Types of holes in metal and methods of drilling them
Types of holes:
- deaf;
- end-to-end;
- half (incomplete);
- deep;
- large diameter;
- for internal thread.
Threaded holes require diameters to be determined with the 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 hole size for drilling
| Metric thread | Inch thread | Pipe thread | |||||||
| Thread diameter | Thread pitch, mm | Threaded hole diameter | Thread diameter | Thread pitch, mm | Threaded hole diameter | Thread diameter | Threaded 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 through it. A special feature of the process is to protect the surface of the workbench or tabletop from the drill going beyond the workpiece, which can damage the drill itself, as well as provide the workpiece with a “burr” - a burr. To avoid this, use the following methods:
- use a workbench with a hole;
- put a wooden gasket or a “sandwich” under the part - wood + metal + wood;
- put under the part metal bar with a hole for free passage of the drill;
- reduce the feed rate at the last stage.
The latter method is required when drilling holes “in situ” so as not to damage nearby surfaces or parts.
Holes in thin sheet metal are cut with feather drills, since a twist drill will damage the edges of the workpiece.
Blind holes
Such holes are made to a certain depth and do not penetrate through the workpiece. There are two ways to measure depth:
- limiting the length of the drill with a sleeve stop;
- limiting the length of the drill with a chuck with an adjustable stop;
- using a ruler attached to the machine;
- a combination of methods.
Some machines are equipped with an automatic feeding system to a given depth, after which the mechanism stops. During the drilling process, you may need to stop work several times to remove chips.
Holes of complex shape
Holes located on the edge of the workpiece (half holes) can be made by connecting the edges and clamping two workpieces or a workpiece and a spacer with a vice and drilling a full hole. The spacer must be made of the same material as the workpiece being processed, otherwise the drill will “go” in the direction of least resistance.
A through hole in a corner (profiled metal) is made by fixing the workpiece in a vice and using wooden spacer.
It is more difficult to drill a cylindrical workpiece tangentially. The process is divided into two operations: preparing a platform perpendicular to the hole (milling, countersinking) and the actual drilling. Drilling holes in surfaces located at an angle also begins with preparing the site, 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 wood plug.
Shouldered 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 of 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 deepening of the hole. With this method it is easier to control the depth of each step.
1. Drilling a hole. 2. Diameter reduction
Large diameter holes, ring drilling
Producing large-diameter holes in massive workpieces up to 5-6 mm thick is labor-intensive and costly. Relatively small diameters - up to 30 mm (maximum 40 mm) can be obtained using conical, or better yet, stepped conical drills. For larger diameter holes (up to 100 mm), you will need hollow bimetallic bits or bits with carbide teeth with a center drill. Moreover, craftsmen traditionally recommend Bosch in this case, especially for hard metal, for example, steel.
This annular drilling less energy-consuming, 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 will want to make a hole on the machine, and with a large number of holes in a sheet more than 12 mm thick, it is better to immediately look for such an opportunity.
In a thin-sheet workpiece, 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 it is necessary to make a deep hole. In theory, this is a hole whose length is five times its diameter. In practice, deep drilling is called drilling that requires forced periodic removal of chips and the use of coolants (cutting fluids).
In drilling, coolant is needed primarily to reduce the temperature of the drill and workpiece, which heat up from friction. Therefore, when making holes in copper, which has high thermal conductivity and is itself capable of removing heat, coolant may not be used. Cast iron can be drilled relatively easily and without lubrication (except high-strength).
In production, industrial oils, synthetic emulsions, emulsols and some hydrocarbons are used as coolants. In home workshops you can use:
- technical petroleum jelly, castor oil - for soft steels;
- laundry soap - for aluminum alloys of type D16T;
- a mixture of kerosene and castor oil - for duralumin;
- soapy water - for aluminum;
- turpentine diluted with alcohol - for silumin.
Universal refrigerated liquid 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, or used, and boil the solution until a homogeneous soap emulsion is obtained. Some craftsmen use lard to reduce friction.
| Processed material | Cutting fluid |
| Steel: | |
| carbon | Emulsion. Sulfurized oil |
| structural | Sulfurized oil with kerosene |
| instrumental | Mixed oils |
| alloyed | Mixed oils |
| Malleable cast iron | 3-5% emulsion |
| Iron casting | No cooling. 3-5% emulsion. Kerosene |
| Bronze | No cooling. Mixed oils |
| Zinc | Emulsion |
| Brass | No cooling. 3-5% emulsion |
| Copper | Emulsion. Mixed oils |
| Nickel | Emulsion |
| Aluminum and its alloys | No cooling. Emulsion. Blended oils. Kerosene |
| Stainless, heat-resistant alloys | A mixture of 50% sulfur oil, 30% kerosene, 20% oleic acid (or 80% sulforesol and 20% oleic acid) |
| Fiberglass, vinyl plastic, plexiglass and so on | 3-5% emulsion |
| Textolite, getinaks | Blowing with compressed air |
Deep holes can be made by continuous or circular drilling, and in the latter case, the central rod formed by the rotation of the crown is not broken out entirely, but in parts, weakening it additional holes small diameter.
Solid drilling is performed in a well-fixed workpiece with a twist drill, into the channels of which coolant is supplied. Periodically, without stopping the rotation of the drill, you need to remove it and clear the cavity of chips. Working with a twist drill is carried out in stages: first, take a short hole and drill a hole, which is then deepened with a drill of the appropriate size. For significant hole depths, it is advisable to use guide bushings.
For regular drilling of deep holes, we can recommend purchasing special machine With automatic feeding Coolant to the drill and precise alignment.
Drilling according to markings, templates and jigs
You can drill holes according to the markings made or without it - using a template or jig.
The marking is done with a center punch. With a hammer blow, a place is marked for the tip of the drill. You can also mark the place with a felt-tip pen, but the hole is also needed so that the point does not move from the intended point. The work is carried out in two stages: preliminary drilling, hole control, final drilling. If the drill has “moved away” from the intended center, notches (grooves) are made with a narrow chisel, directing the tip to the specified location.
To determine the center of a cylindrical workpiece, use a square piece of sheet metal, bent at 90° so that the height of one arm 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 using the theorem - by the intersection of perpendiculars from two chords.
A template is needed when making a series of similar parts with several holes. It is convenient to use for a pack of thin-sheet workpieces connected with a clamp. This way you can get several drilled workpieces 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 jig is used when precision in maintaining the distances between holes and strict perpendicularity of the channel is very important. When drilling deep holes or when working with thin-walled tubes, in addition to the jig, guides can be used to fix the position of the drill relative to the metal surface.
When working with power tools, it is important to remember human safety and prevent premature wear of the tool and possible defects. In this regard, we have collected some useful tips:
- Before work, you need to check the fastenings of all elements.
- When working on a machine or with an electric drill, clothing should not contain elements that could be affected by rotating parts. Protect your eyes from chips with glasses.
- When approaching the metal surface, the drill must already be rotating, otherwise it will quickly become dull.
- You need to remove the drill from the hole without turning off the drill, reducing the speed if possible.
- If the drill does not penetrate deep into the metal, it means that its hardness is lower than that of the workpiece. Increased hardness of 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 carbide with additives and operated at low speeds with low feed.
- If a small-diameter drill does not fit well in the chuck, wrap a few turns of brass wire around its shank, increasing the grip diameter.
- If the surface of the workpiece is polished, put a felt washer on the drill to ensure that it does not cause scratches even when it comes into contact with the drill chuck. When fastening workpieces made of polished or chrome-plated steel, use fabric or leather spacers.
- When making deep holes, a rectangular piece of foam placed on a drill can serve as a meter and at the same time, while rotating, blow away small chips.
Drilling metal is one of the most common metalworking operations. Separable and non-separable connections - rivets, screws, bolts, studs - 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 to mark the hole.
Selection of drills
If holes in metal are drilled for threads, then according to GOST 24705-81, for the most commonly used thread sizes (for standard large steps): M4, M5, M6, M8, M10 and M12 - the diameter of the drills will be equal to 3.3, respectively; 4.2; 5; 6.7; 8.4; 10.2 mm. It is quite acceptable if drilling for threads is carried out with a drill whose diameter 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, P6M5) are designed for drilling metals that do not have high hardness. To drill through metal of increased hardness, you will need carbide drills. Such drills can be made entirely of carbide or have only a carbide tip.
Sometimes before starting drilling it is not known what hardness of the metal is to be drilled. Therefore, if you see at the first moment of drilling that the drill does not penetrate the metal, you must immediately stop drilling, otherwise the drill will be irretrievably damaged by overheating and losing hardness. Evidence of this will be the appearance of a dark blue color on it. Before drilling into metal whose hardness is unknown, you can run a file through it. If the latter does not leave marks on the metal, then the material has increased hardness.
How to drill metal
Low and medium speeds are optimal for drilling most metals - 500-1000 rpm. High speeds quickly heat up the drill, which can result in annealing and softening. 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, and the drill becomes dull very quickly. The rate of dulling of the drill depends, in particular, on the speed, feed force, cooling and other factors, but no matter how hard you try, if it doesn’t drill Aluminium alloy, the time it takes a drill to operate unsatisfactorily is measured in minutes.
Before drilling, you need to mark the hole by tapping it. To do this, you need to place the tip of the center punch (or dowel) in the expected center of the hole and hit it with a hammer. Punching is necessary to prevent the drill from slipping 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 When drilling, it is advisable to dip the tip of the drill in machine oil or drop it into the core site. Oil in the drilling area helps to better cool the drill and makes cutting metal easier. A drill used for drilling using oil becomes less dull, requires less sharpening and lasts longer. A special emulsion, soapy water, and kerosene are also used as a coolant. According to some craftsmen, lard is a good lubricant and cooling agent. Before drilling, a rotating drill is immersed in a piece of lard, which melts during drilling and has a lubricating and cooling effect. But still the simplest and most convenient remedy is soapy water. It doesn't get dirty, and every home has soap. It is enough to drop it once at the beginning of drilling and during the process. You can periodically dip the drill in a soapy solution.
When through drilling with a large feed, a burr (burr) is formed at the exit of the hole, to which the drill clings with its side cutters. As a result, a sharp blocking of the drill and its fracture or chipping of the incisor can occur, and even at this moment the drill dulls especially intensely. Such stops also have a negative impact on the condition of the drill. To avoid burr formation, you need to finish drilling holes in the metal with low feed. It is also advisable to place a wooden block, which prevents the formation of a burr. The block and the workpiece must be pressed tightly against each other. For greater effect, you can place not a wooden block, but a plate of the same or less hard metal, which should be pressed tightly to the point where the drill exits.
Most often it is necessary to drill steel, but often it is necessary to drill other metals that have their own drilling characteristics. Aluminum, for example, envelops the drill, making it difficult for it to penetrate deeper and widening the resulting hole. If you need to drill in aluminum precise hole(for example, for threads), it is necessary to use coolant and remove the drill from the hole more often to clean it. Regular gray cast iron drills relatively easily and does not require coolant or lubricant. But drilling in cast iron can bring surprises. There are high-strength gray cast irons that must be drilled with a drill made of carbide material. White cast iron, whose main structural constituent is cementite, is very hard and 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, it is better to drill a hole with a diameter of 12 mm in two or three steps - sequentially with drills of 5, 10 and 12 mm.
Dull drills need to be sharpened promptly. It is better to do this with a sharpening device, but you can do without it. In this case, you need to pay attention to the symmetry of the drill tip. If the sharpened edges do not meet exactly 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 (angle between cutting edges) is 118°. For drilling aluminum, the optimal angle is 130-140°, 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, you need to maintain the verticality of the drill relative to the metal surface (if you do not need to drill 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 displaced relative to each other - the larger the diameter of the pipe, the more so. It is quite difficult to maintain the perpendicularity of the drill by eye, so you can use homemade 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 the holes match is by drilling them together. When drilling holes for rivets, drilling the assembly is a must. Once you've drilled the first hole, you can use it to bolt the pieces together so you can drill the remaining holes without worrying about the pieces moving relative to each other. If drilling the mating parts in the assembly is impossible or inconvenient, then a jig or guide must be used. You should know that no matter how accurately the mating holes are marked and cored, they will still not coincide absolutely exactly, since when drilling even a cored hole, the drill will move slightly to the side.
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Today everyone home handyman available necessary tool for metal cutting, drilling, stripping. But what if you need to drill a large diameter hole? After all, the maximum cross-section of a conventional drill for a hand-held electric drill is only 20 mm.
Tools for drilling large holes
There are several ways to drill a hole with a diameter greater than 20 mm. For this, special devices are used:
- Cone drill. A large number of openings same size drilling won't work. But for home use quite acceptable. Maximum cross section- up to 40 mm. The thickness of the processed metal is 5-6 mm.
- Tapered step drill. It is more convenient to use, since each step is formed through a smooth spiral transition. When drilling, this makes it easy to track the actual diameter of the hole. With its help you can drill a circle up to 40 mm in diameter on metal up to 6 mm thick.
- Bimetallic crowns - suitable for preparing holes up to 109 mm in steel products up to 5 mm thick. When working, it is strongly recommended to use specialized lubricating and cooling compounds, which will ensure maximum service life cutting tool. An adapter is also required to install the device on an electric drill. On average, using a bimetallic crown, you can drill 5-20 openings - depending on its quality, which, accordingly, is reflected in the cost.
How can you drill a large hole without extra costs?
For this method, you will need a small cross-section drill (5-6 mm is enough), as well as a milling cutter or a used grinding wheel (corresponding to or slightly smaller than the diameter of the hole) for an angle grinder. The option is more labor-intensive, so it takes much more time.
On a metal blank, 2 circles are drawn with a pencil:
- 1 - for the future hole.
- 2 - depends on the cross-section of the drill, that is, when using a 6 mm tool, the diameter of the intended circle will be 6 mm smaller than the previous one.
Along the 2nd circle it is necessary to mark 2 places in opposite places and drill holes with a 6 mm drill. From the resulting openings along the intended line you need to retreat approximately 3 mm and again mark the places for drilling. Holes are drilled along the entire circumference. If necessary, the remaining sections can be cut with a chisel.
The hole will be jagged, so it needs to be bored out. This can be done with an electric drill with a cutter, but it is much more convenient with a grinder using grinding abrasive wheels of a suitable diameter. Using a grinder, you can quickly and evenly bore a hole to the required diameter.
Therefore, you should not throw away used abrasive wheels for an angle grinder with a diameter of even less than 45 mm - they can always be useful on the farm.
To improve the basic characteristics of the metal, it is often hardened. This technology involves increasing the hardness of the product due to strong heating of the metal and its rapid cooling. In some cases, after heat treatment you have to do some drilling. By increasing this characteristic, drilling hardened metal becomes more difficult. Let's take a closer look at all the features of drilling hardened steel.
Drilling a hole in hardened steel
Spreading the question of how to drill hardened steel can be associated with the fact that when using conventional technology the tool quickly becomes dull and becomes unusable. That is why you need to pay attention to the features of drilling hardened alloy. Among the features of the technology, we note the following points:
- It is necessary to properly prepare the hardened workpiece.
- In some cases, a special tool is required.
- Coolant is being used.
If necessary, you can make a drill for hardened steel with your own hands, which requires certain equipment and skills. However, in most cases, a purchased version is used, since it will cope better with the task when cutting hardened steel.
Nuances when drilling
The technology in question has a fairly large number of features that need to be taken into account. Drilling of hardened metal is carried out taking into account the following points:
- Before carrying out work, pay attention to the hardness of the surface. This parameter is used to select the most suitable drill. Hardness can be determined using a variety of technologies.
- During drilling, a large amount of heat is generated. This is why rapid wear of the cutting edge occurs. In this regard, in many cases, cooling liquid is supplied to the cutting zone.
- When cutting difficult-to-cut material, it is necessary to sharpen the cutting edge from time to time. For this purpose the usual sharpening machine or a special tool. Only diamond-coated wheels are suitable as an abrasive.
There are the most various methods cutting hardened steel. Some of them significantly simplify the processing. Only by taking into account all the nuances can the quality of the resulting hole be improved.
Useful drilling techniques
For working with hardened steel, the most various technologies. The most common technologies are characterized by the following features:
- Surface treatment with acid. This technology is characterized by long-term use, since it takes quite a lot of time to reduce the surface hardness. Sulfuric, perchloric or other acid can be used for etching. The procedure involves creating a lip that will contain the substance used in the cutting zone. After prolonged exposure, the metal becomes softer, it will be possible to drill when using the usual version execution.
- Can be used welding machine to achieve the set goal. When exposed high temperature the metal becomes softer, which greatly simplifies the procedure.
- Most often, a special drill is used. There are versions on sale that can be used for processing hardened steel. In their manufacture, metal with increased resistance to wear and high temperatures is used. However, the complexity of manufacturing and some other points determine that the cost of a special tool is quite high.
In addition, to achieve this goal, a punch is often purchased. It can be used to make a small hole, which will simplify further drilling.
Use of lubricants
When drilling through hardened steel, serious friction occurs. That is why it is recommended to purchase and use various lubricants. Among the features similar method processing, we note the following points:
- First, the drilling area is processed. A small amount of lubricant is applied to the surface where the hole will be located.
- Oil is added to the cutting edge. To process hardened steel, a small amount of the substance is required, but it must be added from time to time, since it scatters when the tool rotates.
- During work, it is recommended to take breaks to cool the cutting surface and the surface being processed.
Special oil not only simplifies drilling, but also increases the service life of the tool used.
This is because oil can reduce the temperature of the cutting edge.
Drill selection
Twist drills, which are represented by a vertical rod with two grooves, have become quite widespread. Due to the specific arrangement of the grooves, a cutting edge is formed. Among the features of the choice, we note the following points:
- The pobedite drill bit has become quite widespread. It can be used to work with various hardened alloys. However, a surface with too high hardness cannot be processed with such a tool.
- The choice is also made based on diameter. It is worth considering that it is quite difficult to obtain a large diameter hole. The larger diameter option is much more expensive due to the application large quantity material during its manufacture.
- Attention is also paid to the sharpening angle, the purpose of the product and the type of material used in manufacturing. For example, cobalt versions are characterized by more high stability to exposure to high temperatures.
- It is recommended to pay attention exclusively to products famous manufacturers. This is due to the fact that Chinese options designs are manufactured using low-quality materials. However, such an offer is much cheaper and can be used for short-term or one-time work.
- When choosing a drill, you can be guided by the markings. It can be used to determine which materials were used in production. The diameter of the hole that can be obtained when using the tool is also indicated.
In a specialized store you can find almost everything you need to carry out the work. However, enough high price products and some other points determine that some decide to make a drill themselves from scrap materials. Similar work can be done if you have the required tools.
Making a homemade drill
If necessary, a drill can be made from hardened steel. Among the main recommendations for conducting similar work note:
- Rods are selected that are made from tungsten and cobalt alloys. People call this metal victorious. Compared to a conventional drill, this version is characterized by increased wear resistance.
- To process the workpiece, you need to secure it in a small vice. Otherwise, the work will be quite difficult.
- To sharpen such a surface, a diamond stone is required. The usual one will not withstand long-term work.
- The end surface is sharpened in such a way as to obtain a surface resembling flat screwdriver. After that cutting edges sharpened to obtain a sharp tip.
In order to reduce the degree of surface machinability, oil is added. This ensures long-term processing due to reduced friction and lower temperature.
In conclusion, we note that processing of hardened steel should be carried out exclusively when using special tools. The work requires a drilling machine, since a manual one will not allow you to get the required hole.