Circular saw (crown) for wood, concrete, metal: dimensions, sharpening. Hole Saw Hole Saw Teeth Types

Some people reasonably call a hole saw for wood as an end mill - the material is processed in almost the same way, and outwardly the tools are similar. The equipment under consideration, although it leaves a lot of shavings, allows, using a conventional power tool, to obtain clean through holes in the tree.

Hole saw device for wood

The saw blade of such a saw is a cutting crown, the number and profile of teeth of which depends on the strength and relative humidity of the wood. Most manufacturers of hole saws for wood produce bits in sets, which allows the tool to be used for processing drywall and even metal.

The saw blade itself consists of two sections: the cutting head and the shank. For the manufacture of bimetallic cutting heads, which are intended for work in wood, high-quality tool steel of the 11ХФ, ХГС or 9ХВГ type is used, while the cutting bit for metal works can also be made of carbide. The shank is made from hardened structural steel such as 45 or 40X steel, and is brazed to the cutting end with a high-strength brass alloy. On the opposite side, the shank is equipped with a seat for an electric drill chuck. For conventional clamping tools, the end part of the shank is hexagonal, and in newer models it is integrated under the keyless chuck.

Since a significant amount of chips is formed during the processing of wood with a hole saw, a spring is provided in the design of the tool, with the help of which the chips stuck between the teeth are removed outward.

The technological parameters of the hole saw for wood are:

The height of the working part of the crown, on which the depth of the volume of wood, removed by the saw in one pass, depends. It is standard by default and equals 40 mm. Depending on the hardness and graininess of the wood, this makes it possible to obtain cavities up to 35 ... 38 mm deep.
Outside diameter of the cutting part of the crown. The sets include crowns in sizes from 30 mm to 150 mm. The installation possibilities are determined by the engine power and the possibility of adjusting the speed: for hole saws for wood with a diameter of more than 110 mm, the speed of the drill must be reduced to a minimum, or a special stand must be used.
The profile of the teeth, which depends on the material being processed and the principle of operation of the bit. There are reversible saws that allow you to change the direction of their rotation. Such saws are more convenient for the master, since they make it possible to hold the drill while working with both the left and right hand. However, with prolonged operation, they heat up more, and as a result, they begin not to cut the tree, but to rip off the surface layer from it, deteriorating the quality of processing. The profile of the tooth in such saws has the shape of a triangle in plan, expanding towards the base.

Features of operation

Due to the high contact area between the saw and the wood, the tool gets very hot during operation. Therefore, long-term non-stop operation of a drill with a hole saw on wood is impossible (unless, of course, an air or water cooling system is adapted).

Hole saws are often called typesetting, which is explained by the integral design of the tool. For such a tooling, the method of connecting the shank to the cutting part is very important. Possible options:

Flat soldering. In this case, the hole saw for wood will withstand the minimum possible shear loads, and it should be used for a short time, removing the minimum amount of material per pass. The diameter of the nozzles usually does not exceed 30 mm.
Brazing with a shank fit into the seat of the bit. The fixing reliability increases, so these saws are produced with an increased diameter - up to 127 mm, and they can be used for longer.
Same as in the previous case, but the shank additionally rests on a shoulder in the upper part of the bit. This option is implemented in the designs of hole saws with a size of 150 mm and more (saws with a diameter of up to 210 mm are known), since the thermal expansion of the material during the operation of the saw will not cause deformation of the typesetting tool.

In the practice of their use, hole saws for wood are installed in special glasses of a revolving type, which, when turned in a chuck, put a crown of the required diameter on the processing line. A union nut is used to ensure fixation, and a drill, which is included in any kit, is used to center the hole to be drilled. The drill protrudes beyond the working surface of the teeth, and this ensures the required alignment of the blind hole. However, such a design requires a change in the number of revolutions of the drill shaft: at the initial stage, when working with a drill, the required torque is small, so it is more rational to increase the number of revolutions. Then, when the teeth of the circular saw for wood come into action, the load increases sharply, so the number of revolutions of the drill is reduced.

for preliminary drilling - 1750 ... 2000 min -1;
to obtain a blind hole - 750 ... 1000 min -1;
for finishing the generatrix of the resulting hole, its countersink and other similar operations - 1000 ... 1500 min -1.

How to choose the right hole saw for wood?

Since when working with the tool in question, significant shear forces constantly arise, preference should be given to circular saws, the design of which provides solutions that ensure the necessary accuracy of work. Thus, the presence of centering pins made of hardened steel on the bearing surface of the shank provides additional centering of the bit. In this case, the height of the pin must be at least two of its diameters.

It is desirable that the kit includes an ejection spring, which makes it easier to work when it is necessary to obtain blind holes in fibrous wood (ash, pear, hornbeam).

If, in practice, hole saws for wood are supposed to be used to obtain blind holes with a diameter of more than 70 ... 75 mm, additional threaded nozzles will be useful, which are fixed with screws to the bottom of the glass with a set of crowns. The number of screws should be at least three, while it should be noted that the attachments should be selected from the same manufacturer. The diameter of the nozzle should not be too large (more than 45 mm), since in this case the inertia of the set as a whole increases, and the power of the drill may not be enough.

By the way, about the power. Despite the fact that the processed material is wood, the presence of shavings and increased friction of the teeth against the walls of the hole create additional braking torque for the electric motor. This negatively affects the operating time and the longevity of the drive. Therefore, the minimum power of the drill for working with a hole saw on wood should not be less than 1000 W.

Circular saws

TO Category:

Woodworking machinery

Circular saws

Circular saws use circular saws with a diameter of up to 800 mm and a thickness of up to 2.5 mm. In addition to saws, cutters are installed on formatting machines.

Depending on the profile, circular saws are divided into flat (Fig. 1, a, b), in which the thickness of the disc is the same throughout the section, and into saws "with an undercut", that is, with a thickened peripheral part of the disc (Fig. 1, v). Undercut saws are called planing saws. Saws are also used, on the tips of the teeth of which hard alloy plates are soldered (Fig. 1, d).

Saws with carbide plates are widely used in the woodworking industry for processing furniture blanks, cutting and sawing boards, plywood, veneered panels, for sawing solid and glued wood. The durability of the teeth of such saws is 30 - 40 times higher than the durability of the teeth of alloy steel saws. The saw diameter decreases slightly due to regrinding. The kerf when sawing with tools with tungsten carbide blades is slightly larger than the kerf obtained when sawing with conventional saws, but this (especially when cutting sheet materials) does not matter much, in addition, the appropriate preparation of saws with tungsten carbide inserts (grinding of the side edges plates after soldering) allows you to get a high quality cut surface, which compensates for the loss of wood to sawdust.

Rice. 1. Circular saws: a - general view, b - flat saw profile, c - planer saw profile, d - saw tooth with a hard alloy plate

The outer diameter D of circular saws is called the diameter of the circle drawn along the tops of the teeth. Each circular saw has an internal hole for mounting it on the saw shaft. The diameter of this hole is the inner diameter d of the saw blade and must match the diameter of the saw shaft. A gap of no more than 0.1 - 0.2 mm is allowed between the saw shaft and the hole.

The machine operator chooses the saw according to the material to be cut. For example, when cutting chipboard and fiberboard, saws with hard alloy plates or with fine teeth are used. For longitudinal sawing, saws with a tooth profile I w II are used (Fig. 2, a), for transverse - with a profile III and IV (Fig. 2, b). The diameter of circular saws is selected depending on the thickness of the material, and the profile - on the required roughness of the cut. So, if the surface is intended for gluing (for example, on a smooth jointer), planing saws are used.

Rice. 2. Profiles of saw teeth a - for longitudinal sawing, b - for pepper sawing

Rice. 3. Checking the forging of circular saws: 1 - saw, 2 - ruler

Saws should be used with the smallest diameter for the cutting conditions, as this will reduce power consumption, kerf and set teeth. Saws of small diameters are more stable in work, give a better quality of the cutting surface, their teeth are easier to sharpen, and the dressing of the saws is also easier.

The requirements to be met by circular saws are as follows:

1. The saw blade must be forged, that is, its central part is somewhat weakened by hammer blows on both sides of the squeak laid on the anvil. You need to forge flat saws with a diameter of 250 mm and more. The correctness of forging is determined with a straight edge, laying it on the disk in the direction of the radii (Fig. 3). There should be a gap between the ruler and the saw blade in its central part, the same for any position of the ruler. In the case of poor forging, with one position of the ruler between it and the disk, a gap is obtained, with the other, there is no gap or a bulge appears.

The amount of clearance characterizes the concavity of the saw and depends on its diameter and thickness.

The need for forging saws is explained by the conditions of their work. During the sawing process, the saw teeth, in contact with the wood, heat up and, if the center of the saw is not weakened by hammering, the saw blade bends. If the curvature is significant (it crosses the boundaries of elastic deformations), then the shape of the disk is not restored even when it cools. With correct forging, the crown of the circular saw, when heated, somewhat increases its size due to the weakened middle. This saw is stable in operation.

2. The teeth of a flat saw must be set apart, that is, their tips must be bent alternately: one tooth to the right side, the adjacent one to the left. The amount of divorce on one side is 0.3 - 0.5 mm. Saw blades designed for longitudinal sawing of dry wood and hard deciduous wood have a smaller gap, a larger one - saws for sawing freshly sawn softwood and soft deciduous wood.

Tooth set can be replaced by crimping. When flattening, the width of the tines, which are given the shape of a spatula, increases. Crimped teeth are more stable and less blunt than set teeth; energy consumption when using them is reduced by 12-15%.

3. Saw teeth must be sharply sharpened. Large burrs and curls of the ends are not allowed. Saw teeth for cross-cutting should be sharpened at an angle of 40 ° for soft woods, 60 ° for hard ones, and their tops should be spaced from one another and from the center of the blade at the same distance.

4. Saws with at least one broken tooth or cracks on the peripheral part of the disc are considered defective, install them on. the machine is prohibited.

Before installing the saw blade, carefully clean the washers and the shaft journal with a rag or ends and check the bearing surfaces of the washers. If even slight protrusions are found on the bearing surface, the washers are replaced.

If the diameter of the inner hole of the saw exceeds the diameter of the saw shaft by more than 0.1 - 0.2 mm, insert sleeves should be used for precise positioning of the saws. The saw is fixed on the shaft with washers and nuts.

Circular flat saws for cross cutting with a set of teeth (Fig. 1, a, b) are used for preliminary facing of the part, since high quality sawing is not required here. For fastening to the spindle, the saw has a bore, the diameter d of which depends on the diameter of the blade D and the thickness of the saw b. The number of saw teeth must be 48, 60 or 72. The crosscut tooth profile is shown in fig. 1, b. The teeth should have lateral oblique sharpening along the front and back edges, as well as a negative front contour angle equal to minus 25 °.

Rice. 4. Circular saws: a - general view, b, c - for cross cutting

In this case, the angle of sharpening of the side cutting edges of the tooth, measured in the normal section to the edges, should be 45 ° when sawing softwood and 55 ° when sawing hardwood. Circular saws with carbide inserts are used for transverse processing. Saw teeth are made with an inclined back surface, as shown in fig. 4, e. Depending on the inclination, when looking at the tooth from the front, saws are distinguished, left, right, or with a symmetrical alternating inclination.

Solid steel rip saws are shown in fig. 4, d, and with carbide plates - in Fig. 4, e. Circular saws for mixed sawing should have teeth, the front contour angle of which is 0 ° (Fig. 4, e).

If high quality sawing is required, planing saws with a negative rake angle are used (Fig. 4, g), as well as carbide saws with an alternating symmetrical inclination of the flank surface of the teeth.

Preparation for work of circular flat saws includes dressing, sharpening and setting of teeth. Saws after preparation for work must meet the following requirements. The number of teeth and their profile must correspond to the type of sawing. The saw blade must be flat. The deviation from flatness (warpage, bulges, etc.) on each side of the disc with a diameter of up to 450 mm should be no more than 0.1 mm. The flatness of the saw is checked with a straight edge or on a special device.

The required angular parameters of the teeth and the sharpness of the cutting edges must be ensured by sharpening. Sharpened teeth should not have a gloss at the corners formed by the intersection of the cutting edges of the cutter. Gloss indicates that an insufficient metal layer has been removed from the tooth during sharpening. The difference in the size of the front angles and taper angles is allowed no more than ± 2 °.

The roughness of the end surfaces of the saws and the surfaces of the bore should be microns. The cutting teeth of a sharpened saw must be free of burrs, breaks and twists. Burrs from the lateral edges of the teeth are removed with a fine-grained abrasive bar. The quality of sharpening of saws is checked with a universal goniometer or a template for checking the angular elements of the teeth. The tops of the teeth should be located on the same circle with a deviation of no more than 0.15 mm. To align the gear rim in height and width, the saw teeth are planed, i.e. grind the material off the tips of the most protruding teeth when the saw rotates at the operating frequency.

After sharpening, the teeth of the steel saws are bred. At the same time, the tips of the adjacent teeth are bent in different directions by 1/3 of their height (counting from the top). The amount of bend of each tooth (spread on the side) is set depending on the cutting mode and wood species. For cross-cutting with saws with a diameter of 500 mm, the spread per side should be 0.3 mm for dry wood and 0.4 mm for wood with a moisture content of more than 30%. The accuracy of the setting of the teeth is controlled by an indicator water meter or a template. Permissible deviation ± 0.05 mm.

Preparation for work of circular saws with carbide plates consists in soldering the plates, sharpening and finishing the teeth. Moreover, they must be balanced. Imbalance of the blades due to their uneven thickness can cause a loss of stability of the saw blade during operation, strong runout of the spindle and unsatisfactory cutting quality.

The strength of the soldering is checked by testing the saws with rotation at a peripheral speed of the teeth of at least 100 m / s. Sharpening and debugging of saws equipped with carbide plates is performed on semi-automatic machines of increased accuracy and rigidity. Pre-sharpening is carried out with abrasive (carborundum), and final sharpening and lapping - with diamond wheels.

The static balancing of the saws is carried out on a special device. The imbalance of the disk is characterized by a residual imbalance, which is equal to the product of the unbalanced mass by the value of its displacement relative to the axis of rotation (eccentricity). The amount of residual unbalance depends on the diameter of the saw blade.

Types and sizes of saws.

The shape of the teeth of circular saws depends on the cutting direction and the hardness of the wood being cut. For longitudinal sawing, oblique teeth with a straight, broken (wolf tooth) and a convex back are used; for cross cutting - isosceles (symmetrical), asymmetrical and rectangular.

Teeth with a broken and convex back are more stable than those with a straight back, so saws with such teeth are used for sawing hardwood. Softwood and softwood can be cut with saws with straight-back teeth. In fig. 31 shows a method for determining the angles of a circular saw tooth.

Rice. 5. Profiles of teeth of circular saws: a - for longitudinal sawing; b - for cross cutting

When spreading, the tops of the teeth are bent by 0.3-e-0.5 of their height. A fracture of the back of a wolf's tooth is made from the apex at a distance equal to 0.4 of the step size. Sharpening teeth for longitudinal saws

sawing - straight continuous, with saws for cross-cutting - oblique through the tooth at an angle of 65 - 80 ° to the plane of the saw.

A special type of circular saws are planing saws. They are used to obtain a clean cut that does not require planing.

The thickness of the planer circular saw gradually decreases from the ring gear to the center over 2/3 of the radius at an angle of 8 - 15 °. Therefore, the saw teeth are not set apart; cutting edges at the teeth are the front short and side. The teeth of planing saws are group, or, as they say, are notched with "combs". Each group (comb) has a large "working" tooth with an angle of sharpening of 45 °. This tooth cuts wood. Behind the working tooth, there are 3 to 10 fine teeth with a taper angle of 40 °. The shape of the teeth of planing saws for rip and cross sawing is different.

Rice. 6. Determination of the angles of the circular saw tooth

The industry produces planing saws with a diameter of 100 to 650 mm, and a thickness of a ring gear from 1.7 to 3.8 mm. Planer saws have been used more and more in recent years.

Rice. 7. Planing saws

Installation and fastening of circular saws. The circular saw is attached to the working shaft using two clamping washers (flanges), of which one is usually milled together with the shaft; its clamping plane is strictly perpendicular to the shaft. The second washer is tightened with a nut in the direction opposite to the rotation of the saw, to prevent it from unscrewing during operation.

Washers should not protrude above the plane of the work table.

The nut must be tightened firmly until it stops. A saw installed in the machine, when lightly tapped on it, should emit a clear, clear sound.

The cutting height when using a circular saw is approximately equal to 1/3 of the saw diameter.

When choosing a saw, depending on the thickness of the material intended for sawing, you can be guided by the following ratios (dimensions in mm):

material thickness: 60 80 100 120 140 160 200 220 240 260 saw diameter: 200 250 300 350 400 450 500 600 650 700

Such ratios of the thickness of the material to be cut and the diameter of the saw are correct when the material is pushed straight onto the saw or saws onto the material. If the saw is pushed onto the material in an arc, as, for example, in a pendulum saw, the diameter of the saw should be larger.

Requirements for circular saws and their care.

The saw blade must be well ground, free from cracks, bulges and burns. The teeth must be sharply sharpened and evenly spaced; burrs, burns are not allowed on them. The teeth of machine saws for longitudinal cutting are often riveted or flattened instead of being divorced, that is, their ends (tops) are broadened by blows or pressure. For this, special riveters and conditioners are used. Riveting and flattening of teeth in most cases is done with large circular and wide band saws.

When working with a well-sanded disc, friction between the disc and sawdust falling into the cut is reduced, so the disc heats up less.

If it gets too hot, the disc may warp. Bulges will form on it, which will quickly heat up, as a result of which local steel tempering occurs, so-called burns occur. Such burns can be identified by their darker color, by placing a ruler on the saw, or by touch.

A saw with burns is not suitable for work; it must be straightened with hammering.

The circular saw is forged on both sides on the anvil with a hand-held hammer. The parts of the disc surrounding the burn (bulge) are forged, and not the burn itself. The forging begins from the areas most distant from the burn, gradually approaching it and gradually reducing the force of the blows. The straightened disc must be perfectly flat.

Circular saws often have ring gear stretching, causing the stretched portions to loosen. Such a saw does not give a straight cut; it, as they say, "cuts".

Stretching is eliminated by straightening, i.e. by forging the saw in the middle annular part in the direction from the washers to the ring gear. This achieves some elongation of the middle circular part of the saw. The straightening is repeated from time to time. Straightening is done on a planed cast-iron plate with a handbrake, selected by weight at the rate of 1 kg per 300 saw diameter.

If the saw has only one small crack, then in cases where it is impossible to replace it with a completely serviceable saw, a small hole is drilled at the end of the crack; this prevents an increase in the length of the crack - such a saw can continue to work. However, such a measure is always forced, temporary, it is impossible to resort to it constantly.

The industry produces circular saws with balanced rotating parts. The saws are also balanced. However, in the future, the balance may be disturbed due to the grinding of the saws, due to the replacement of some parts of the machine (working shaft, washers, nuts).

The balance of the saws is checked on parallel horizontal balancing blades. The working shaft laid on the knives with the saw blade mounted on it is turned by hand around the axis of rotation, stopping it in various positions around the circumference. If the shaft with the disc at all such stops remains stationary in the position given to it, then it is considered balanced. If the shaft makes some additional rotational movement, then this indicates its insufficient balance.

Cutting a round hole in any material has never been a problem - especially today, when craftsmen have such a device as a hole saw in service. In almost all cases, this is a drill or rotary hammer attachment that can handle almost any type of material. It is with this tool that we will get acquainted in this article, we will study the varieties of this type of tool, understand its purpose and features, and also conduct a short excursion into the field of its practical application.

Hole saw: wood and drywall are no problem

Yes, yes, for drywall and wood, a hole saw of the same type is used - outwardly it resembles a thin-walled tube, at the end of which there are standard teeth for a hacksaw. The hole saw for wood or drywall is produced in two versions - in either case, these are sets that allow you to cut holes with a diameter of 20 to 60 mm.

Both types of these saws have some operational differences. The first version is usually made of relatively thick steel and lasts much longer than the second version of the drywall hole saw, which has a slot along its entire length. The second option is disposable devices that are designed to work at one facility.

It is quite simple to use both the one and the other crown on drywall or wood. They are mounted on a drill or screwdriver and, in essence, work like a conventional drill. There is one small nuance in their design - the diameters of the saws are deliberately made less than, for example, the landing diameter of the socket for drywall. This is done so that the socket fits snugly into the hole and does not wobble in it. On the other hand, if such a socket has to be mounted in a wooden wall (lining or OSB), then the hole obtained by means of a hole saw must be additionally refined with an electric jigsaw. This point should be taken into account - perhaps cutting a hole in a tree with a jigsaw will look much more attractive.

Hole Saw Set: Cut a Round Hole in Metal

By and large, a metal hole saw is not much different from a similar tool for wood or drywall - the main difference between them lies in the steel from which it is made and the shape of the tooth. You yourself understand that metal is a solid thing, and in order to cut through it, the steel of the saw must not be inferior to it in strength. This is usually high speed steel. As for the tooth, it is small and has a special sharpening. In all other respects (in the sense of externally and constructively) it is still the same crown, or rather a set of crowns installed on a special device, which, in turn, is installed in the chuck of a drill or screwdriver.

Almost all metal crowns have several specific points in their work. Firstly, they are not designed for drilling thick metal - as a rule, they are designed to work with thin sheet materials such as galvanized steel or products from it such as metal tiles, metal siding or profiled decking. Secondly, cutting holes with such crowns should not be carried out at high speeds - a high rotational speed of a drill or screwdriver simply burns the saw, and it goes to waste. In turn, a low rotation speed is also not good - no one needs a long drilling process. This means that you need to choose medium drilling modes - including the feed, or rather the effort that the master will apply to the tool in the process.

Crown for a perforator for concrete: features of the tool

In a way, it is difficult to call a drill bit for concrete for a perforator a hole saw, since there is very little in common between them - except perhaps a tubular structure with a drill in the center. Instead of the standard saw cutting teeth, this bit is equipped with a carbide tipped, which is able to withstand both the friction and impact of the hammer drill. There is no need to talk about sets here, since a separate tool of this type has to be purchased for different hole diameters.

The bit for drilling holes in concrete, despite its power and ability to crush concrete walls, is not able to withstand reinforcement. When it hits the reinforcement, which happens almost every time during the drilling process, the solders fly off and, by and large, the expensive tool becomes hopelessly damaged. I don’t want to say that this is a completely useless tool - you just need to understand that in the process of working, getting on the reinforcement, the crown should be removed and instead of it, a usual lance should be installed on the perforator, which is used to complete the job. Subsequently, the reinforcement can either be bent with a hammer or cut with a grinder.

Articulating hole saw: diamond version

A diamond hole saw could be called versatile if it really handled all kinds of materials. But this is not the case - it is designed exclusively for cutting steel and concrete. Wood, drywall and many other soft materials clog the edges of diamonds, as a result of which they lose their ability to cut even metal with concrete - a paradox, but the same thing happens when using diamond core bits to cut holes in asbestos, slate and aerated concrete. Diamond core bits are sold in stores in sets - exactly the same as hole saws for wood and drywall. That is, a large washer with a drill in the middle (the drill in such crowns has a victorious soldering) and about seven or eight interchangeable hole saws.

In the work, the diamond hole saw also has some features.

First of all, these are all the same average revolutions - a high rotational speed of the hole saw leads to rapid wear of the diamond edge. To be more precise, it is better to cut with such crowns at low speeds.

The second point concerns working with concrete. A diamond does its job better if the surface to be cut is moistened with water. For metal, this moment is not relevant.

Often times, diamond-cut crowns are used to drill holes in ceramic tiles - by and large, this is the only normal tool with which you can arrange neat round holes in tiles. When working with this material, it is necessary to take into account its fragility - so that the tile is not split, it must be drilled from both sides. First, from the front side, and then, when the enamel is cut through, it is necessary to go to the wrong side.

By and large, when cutting each material with a diamond hole saw, there are subtleties and nuances. For example, if we talk about concrete, or rather about reinforced concrete, then here we can note such a moment that, with proper cutting, the reinforcement of such structures for the saw is not a problem. It easily passes through if you increase the speed slightly and stop using water during the drilling process. As soon as the valve is passed, it will be possible to add water again to the work process.

And to conclude the topic of what a hole saw is, there is only one thing to add - an infinitely deep hole cannot be drilled with this tool. As a rule, the drilling depth is limited by the length of the bit, which is the disadvantage of this tool - it is not intended for equipment through holes in walls. If you need to punch through a thick wall, then it is better to turn your attention towards the tubular drill.

You can get a high-quality large round hole in the wood in a fast way. To do this, the master will need a wood crown, with the help of which circular drilling will be provided. In addition to a crown on a tree of large diameter, you will need an ordinary drill and a little time.

The depth of the hole can be from a few millimeters to several centimeters. To compare the effectiveness, it is customary to compare the result from circular drills with crowns, while the latter are 4-5 times more productive, all other things being equal. Wood drill bits are sometimes referred to as hole saws, which reflects the essence of their work.

Scope of the tool

The main task for which a core drill is used for wood is to cut a through hole. In most cases, you will need it for a socket outlet. Also, in addition to a solid wooden surface, you can drill with this or a similar tool in other materials with similar characteristics or hardness:

plywood;
Chipboard or OSB;
plastic bars;
non-ferrous metals;
drywall, etc.

For workpieces that are harder than wood, it is preferable to choose core drills made from high carbon steels (HCS) coated with hard metal spray grains. If you choose high-speed grades (HSS), then it is recommended to give preference to stronger alloys, similar to P12 or P18. They have higher durability than P6M5.

According to the current standards, the crown for socket boxes is chosen with a circumference of 6.8 cm. However, it is often necessary to make larger holes, for example, 150 or 160 mm. Also, for technological or decorative purposes, craftsmen make 200 mm for wood.

To make holes less than 65 mm in diameter, you will need a 19 mm shank holder. If a large wood bit is used, for example 90-110 mm or even 125 mm, then a reinforced holder of at least 3.2 cm in circumference must be used.

The number of teeth on the working part directly depends on the size and dimensions of the tool used. The larger the dimensions, the more teeth.

A positive factor is a clean, smooth cylindrical surface inside, simultaneously with the formation of a large circular hole in a short time interval. The inner surface after the work of the tool does not require additional processing, deburring, since the high cutting speed removes all possible flaws.

An important quality is that the selected area does not need to be pre-centered or reamed around the perimeter to facilitate cutting and reduce stress. Accordingly, the final quality increases, and the processing speed increases.

Distinctive features

Regardless of what material the crown purchased in Leroy Merlin will be used for, it has a typical design like all the others. It consists of the following elements:

cutting head;
elongated cylindrical or ribbed shank;
guide drill.

The kit can be supplemented with a hex key for high quality core drill clamping.

Manufacturers offer two options for the design of wood core bits for deep drilling:

non-separable construction made of solid metal for making holes of the same size, for example, diameter for wood 120 mm

a collapsible design, which consists of a holder with a shank, to which a cutting ring of the required diameter is attached, for all mounted crowns there is a table in the instructions for use.

In the first version, a one-piece ring is used, and in the second, an open ring in the form of a split cylinder. Rapid ring change speeds up any machining process. Each cutting element has special technological holes for the removal of chips. They are made in the form of circles or slots on the lateral surfaces of the cylinders for small tools in diameter and additionally at the ends for large ones.

Some craftsmen make their own wood crown in their workshops, using a thick-walled metal pipe of the selected diameter.

Preparatory operations for work

It should be borne in mind that to prevent rotation, manufacturers form an irregularly shaped socket for seating the tool. More experienced specialists remind that for high-quality fixation it is necessary to tighten the thrust nut or bolt well. This will allow the cutting tool to be securely held in the grooves and not to loosen, deforming and bending the hole.

Install the tool in the drill chuck only after all threads have been tightened. Then you can start drilling at the selected point. The process practically does not differ from working with a classic drill. It is important during the operation to maintain the maximum perpendicularity to the axis of rotation of the processed plane. This factor is maintained at the first millimeters, then everything goes along the initially formed cylinder.

The number of revolutions for crown rotation is also set in advance. It should be borne in mind that an increase in the diameter of the tool is combined with an increase in its vibration. This forces the use of more powerful drills, if you take wood drills for large holes and large diameters. If possible, an additional handle is fastened to support and maintain perpendicularity.

When setting the rotational speed on a drill, you need to be guided by the following rules:

softwood can be processed at speeds from 1000 (diameter 3.0-5.0 cm) to 2400 rpm (diameter 10-55 mm);
for hard wood, it is desirable to increase the speed to 250 rpm (3.0-5.0 cm) to 600 rpm (1.0-1.5 cm);
using bits with carbide tipped, it is impossible to lower the speed below 400-500 rpm, as the cutting edge will crumble.

VIDEO: How to drill a large hole

Popular brands of wood crowns

Ready-made kits are easier and safer to use. Below are 4 of the most popular sets in the segment at a very reasonable price.

Bison 29554-H15_z01

Consists of 15 items, the price is 950 rubles. The set contains tools for machining diameters from 1.9 to 12.7 cm. There is a centering drill made of HSS steel. Provides good rigidity when working with all types of wood. Also suitable for plastic, drywall, chipboard, etc.

MATRIX 70472

Hole saw set for wood

The set contains 12 items with diameters of 19-127 mm. Price per set - 540 rubles. The material used is carbon steel. Everything is folded into a convenient plastic case for storage and transportation. There is a centering drill and a pair of toolholders. The total weight is 1 kg. The maximum drilling is possible at 2.8 cm.

Bosch 2609255634

The crown crown costs 1230 rubles. Fits perfectly with any drill model. Drills wood, plastic and drywall. The set contains 6 items from 46 to 81 mm in diameter. The holder is included with the centering tool. The permissible drilling depth is 3.1 cm. The weight of the set is 0.5 kg.

For 500 rubles. the buyer of the online store receives 16 items in a convenient case in the basket. The plastic wrap hides two tool holders, a center drill, 19 to 127 mm crowns and a wrench. The total weight of the package is 1 kg. Perfect for homework as there are many positive user reviews.

VIDEO: Forstner's drill or how to make blind holes

The carbide tipped hole saw is used to cut round holes in tiles, stone, cement slabs, etc., and is essential for tiling around water faucets and pipes, and for trimming tiles around the corners of sinks. This tool cuts both soft and hard tiles, although cutting glazed tiles is quite slow.

The hole saw is fastened to the electric drill using a chuck, where also a center drill with a diameter of 6 mm with a carbide tip is inserted. You can saw dry, but if you drill a hole in a separate, not fixed tile, it breaks easily... This is because the hole saw cuts rather slowly and causes the chip and dust to heat up around the hole to be cut. (Thermal shock is not a problem for other saws. Electric tile saws cut the blade with water, and the dry diamond blade is free of teeth and cuts fast enough to avoid dust build-up so that the tile does not get too hot.)

To prevent the tile from overheating during drilling, it is dipped in a container of water... Water washes away heated dust and debris and cools the tiles, protecting them from damage; the use of water also prolongs the life of the cutting tools.

Unfortunately, the immediate the proximity of water and electricity can be dangerous... Battery-powered tools do not pose the same hazard as mains-powered electrical tools, but in most cases they do not have the power and speed required to produce even, smooth cuts on tiles or stones. (If you choose to use a battery-powered drill, then be sure that the power source, consisting of batteries, will run out quickly, since drilling holes requires a lot of electricity).

The solution to the problem is what is needed connect your power tools that you constantly use to protective shutdown device (RCD), which automatically disconnects the tools from the mains in the event of a leak. You can plug into an existing grounded outlet or buy or rent a portable version of the RCD.

To hold the tiles in place while cutting, make a plywood box a bit larger than the tiles and insulate the corners. It is better to fill the box with water so that the tiles are covered with a layer of water of about 5-6 mm. Before submerging the tile, tap the center of the tile lightly with a center punch to create a puncture in the enamel and prevent the center drill from slipping. Then sink the tile by centering the drill bit and turn on the drill at normal speed. As soon as the drill passes through the tile, the hole saw is lowered to the surface of the tile and the rotational speed of the drill must then be reduced.

Be careful not to apply too much pressure to the saw when cutting, as this may shatter the tiles. .Let the hole saw go into the tile itself. Since it is best to cut with a hole saw between 100 and 200 rpm, it is a relatively safe tool. However, it can cut through skin and bone and should be handled with care.