To make the drills sharp - how to make a sharpening machine with your own hands. Homemade tools for sharpening drills Sharpening for drills with your own hands

If only wood has to be drilled, then you don’t have to think about the sharpness of the drill, since the drill can regularly serve for months and years without sharpening. But when it comes to drilling metal, the sharpness of the drill becomes very important, in other words, you can only drill through metal with a sharp drill. It's easy to feel the difference with a brand new drill. Having started to crash into the metal quite quickly, every minute the drill will plunge into the metal more and more slowly, and you will have to put pressure on it more and more. The rate of drill blunting depends in particular on revolutions, feed rate, cooling and other factors, however, no matter how hard you try, the time it takes for a drill to work to unsatisfactory performance is measured in minutes. If the amount of work is significant, it will be expensive to constantly buy new drills, so it is better to learn how to sharpen them. Although it is still worth having several drills of the same diameter (3-10, depending on the diameter and, accordingly, the price) in order to return to sharpening only when all the drills have become dull.

At the periphery of the drill, the cutting speed is maximum, and, consequently, the heating of the cutting edges is maximum. At the same time, heat dissipation from the corner cutting edge very difficult. Therefore, blunting starts from the corner, then spreads to the entire cutting edge. Its rounding is clearly visible. Then the back edge is abraded. Strokes appear on it, risks coming from the cutting edge. With wear, the risks merge into a continuous strip along the cutting edge, wider at the periphery and tapering towards the center of the drill. The transverse cutting edge collapses when worn.

At the beginning of blunting, the drill makes a sharp creaking sound. If the drill is not sharpened in time, the amount of heat generated will increase and the wear process will go faster.

To make it easier to control the geometry of the drill, the main thing to do is the template described below. With its help, even if sharpening is performed without tools, you can always check where else you need to remove the metal, and, in the end, get what you should get (it cannot be that it doesn’t work out, even if you have to grind off half the length of the drill) . To maintain symmetry, try to keep the sharpening time of each section and the pressing force constant.

Sharpening twist drills

The drill is sharpened along its back edges. It is very important that both feathers (teeth) of the drill are sharpened exactly the same. Doing this manually is very difficult. It is also not easy to manually create the required shape of the back face and the specified clearance angle (see below for which angle).

For sharpening there are special machines or fixtures. If possible, it is better to sharpen drills on specialized equipment. But in a home workshop, such an opportunity, as a rule, does not happen. Drills have to be sharpened by hand on an ordinary sharpener.

Depending on what shape the back surface is given, there are different types sharpening: single-plane, two-plane, conical, cylindrical, screw.

With single-plane sharpening, the back surface of the pen is made in the form of a plane. The back angle with such sharpening should be 28-30 °. With single-plane sharpening, there is a high risk of chipping of the cutting edges. This method, the easiest to do with manual sharpening, is recommended for drills up to 3 mm in diameter.

Universal drills with a diameter greater than 3 mm are usually subjected to conical sharpening. In order to understand the features of such sharpening, consider the scheme of conical sharpening on a drill machine with an angle of 2φ of 118 °. The figure below shows a grinding wheel and a drill pressed against its end with a cutting edge and a back surface.

Imagine a cone, the generatrix of which is directed along the cutting edge and the end of the grinding wheel, and the top is 1.9 times its size from the diameter of the drill. The vertex angle is 26°. The axis of the drill intersects with the axis of an imaginary cone at an angle of 45°. If you rotate the drill around the axis of an imaginary cone (as if rolling the cone along the end of the grinding wheel), then a conical surface is formed on the back face of the drill. If the axis of the drill and the axis of the imaginary cone are in the same plane, then the relief angle will be zero. To form a back angle, you need to shift the axis of the drill relative to the axis of an imaginary cone. In practice, this offset will be equal to 1/15 of the drill diameter. Swinging the drill along the axis of an imaginary cone with such a mixture will provide a conical back face and a clearance angle of 12-14 °. The larger the offset value, the larger the relief angle will be. It should be recalled that the relief angle along the cutting edge changes and increases towards the center of the drill.

It is clear that it is very difficult to fulfill all these conditions for sharpening manually. The drill intended for sharpening is taken with the left hand by the working part, possibly closer to the intake cone, and with the right hand by the tail.

With the cutting edge and back surface, the drill is pressed against the end of the grinding wheel and, starting from the cutting edge, with smooth movements right hand, without lifting the drill from the stone, shake it, creating a conical surface on the back face of the pen. Then repeat the same procedure for the second pen.

When sharpening, it is desirable to repeat as accurately as possible the shape of the back surface that was after the factory sharpening, so as not to lose the required back angles.

Another sharpening method, widely used by home craftsmen, is as follows. As in the previous case, the drill is taken with the left hand by the working part as close as possible to the intake cone, and with the right hand by the tail. With a cutting edge, the drill is pressed against the end of the grinding wheel and with a smooth movement of the right hand, without taking the drill off the stone, turn it around its axis, sharpening the back surface. It is very important to maintain the desired angle of inclination to the end face of the grinding wheel when rotating the drill. For this, special bushings are often used when sharpening.

As a result of such sharpening, a tapered surface will be obtained on the back surfaces of both feathers, but a relief angle will not be formed. During operation, the friction of the rear surface against the walls of the hole and, consequently, the heating will be greater.

Due to friction on the grinding wheel, the tool heats up during sharpening. This causes tempering of the hardened part of the tool. The metal softens, loses its hardness. Inept sharpening causes the blade of the tool to become unusable. Therefore, sharpening should be carried out with repeated cooling of the drill in water or in a water-soda solution. This requirement does not apply to carbide drills. Do not use oil for cooling when sharpening. If, for whatever reason, the tool is sharpened dry, then:

a small layer of metal is removed in one pass;
the speed of rotation of the abrasive wheel should be as low as possible;
the drill should never be heated to such an extent that it cannot be tolerated by the hand.

Practice shows that tool sharpening should be carried out against the movement of the grinding wheel. Then the cutting edge is more durable, less likely to crush and break off.

For sharpening, grinding wheels made of electrocorundum (grades 24A, 25A, 91A, 92A) with a grain size of 25-40, a hardness of M3-CM2, on ceramic bonds are used.

In production, sharpening is usually followed by finishing. Finishing makes the surface smoother, removes small notches. A drill that has been honed is more resistant to wear than a drill that has been sharpened. If you have the opportunity to refine, use it.

For finishing, grinding wheels made of green silicon carbide grade 63C with a grain size of 5-6, hardness M3-CM1 on a bakelite bond or ELBOR LO wheels, a grain size of 6-8 on a bakelite bond are used.

One of the basic conditions for a correct sharpening drills a - preservation of its axisymmetry. Both cutting edges must be straight and have an identical length, identical angles at the top (and taper angles) with respect to the axis of the drill.

The correctness of sharpening is checked with a special template.

a - template; b - checking the angle at the top and the lengths of the cutting edges; in - pointing angle; d - the angle between the jumper and the cutting edge.

It is made independently from a sheet of copper, aluminum or steel approximately 1 mm thick. The most durable template, of course, is made of steel. The template checks the angle at the top, the length of the cutting edges, the angle between the jumper and the cutting edge. Instead of the back angle, which is very difficult to measure, the taper angle is measured with a template. It is advisable to make a template before starting to use a new drill in order to transfer the desired angles from the latter.

The uneven length of the cutting edges and their inclination to the axis of the drill also lead to an unequal load. The drill will fail faster due to the intense wear of the overloaded cutting edge.

a - the wedges of the cutting edges are not the same, the middle of the jumper does not coincide with the axis of the drill; b - the cutting edges are sharpened at different angles to the drill axis, the middle of the jumper coincides with the drill axis.

An uneven load on the parts of the drill will cause it to beat during the cutting process and, as a result, an increase in the diameter of the resulting hole.

The easiest way to check the correctness of sharpening is test drilling. If the drill bits are not sharpened equally, then the less loaded one will have less chips from the corresponding groove. Sometimes chips protrude through only one flute. The hole diameter may be exaggerated compared to the drill diameter.

The device consists of a fixed base and a removable holder with holes for drills of different diameters.

1 - rail; 2 - drill; 3 - emery wheel; 4 - base; 5 - holder.

The base is made of a planed board 30-40 mm thick, to which at an angle of 30-32° (depending on the angle 2φ, see below, 30° for 2φ=120°, 32° for 2φ=116°) is sewn (nailed, glued ) wooden lath with a beveled at an angle of 25-30 ° (for single-plane sharpening) side edge. This rail also orients the holder with the drill being sharpened at the right angle relative to the grinding wheel. The holder is made of rectangular wooden block, one of the sidewalls of which is planed at an angle of 60-65 ° (depending on the angle of the side face of the rail). With this sidewall, the holder is pressed against the rail on the base board, which ensures that the front angle of the drill is sharpened within the required limits (25-30 °). On the other sidewall, the holders mark and drill through holes perpendicular to the plane of this sidewall for each drill of one or another diameter. The length of the holder is chosen so that it is convenient to hold it when sharpening drills.

You can’t install a fixture on a regular thrust bearing (armrest), so you have to come up with some kind of table or shelf for it, you can transfer the grinding machine to a table where there will be room for this fixture. On the base, place a holder with a drill inserted into it to be sharpened close to the rail. Rotate the drill in the socket of the holder so that the edge to be sharpened is oriented horizontally. With your left hand, hold the drill at the edge to be sharpened, with your right hand, the drill shank. Pressing the holder against the beveled rail, bring the drill to the emery wheel and sharpen one edge. Then unfold the drill and process the second edge in the same way.

You can do it even easier:

Sharpening angles and other characteristics of the drill

A twist drill is a rod that has two helical grooves to facilitate the exit of chips. Thanks to the grooves on the drill, two helical feathers, or, as they are otherwise called, teeth, are formed.

The twist drill consists of a working part, a neck, a shank and a foot.

A - with a conical shank; B - with a cylindrical shank; a - working cutting part; b - neck; c - pen width; g - foot; d - leash; e - helical chip groove; g - feather; h - shank; and - jumper; L - total length; L 0 - the length of the "working cutting part"; D - diameter; ω - the angle of inclination of the "groove chip screw"; 2φ - angle at the top; f is the width of the spiral ribbon; ψ - the angle of inclination of the jumper.

The working part is divided into cutting and guiding. All cutting elements of the drill are located on the cutting part - the intake cone. The guide part serves as a guide during cutting and is a spare when regrinding the drill. Cylindrical chamfer-ribbons are located on the feathers of the guide part along the helical line. Ribbon serves to guide the drill in the hole, as well as to reduce the friction of the drill against the walls of the hole. It doesn't have to be wide. So, the width of the drill bit with a diameter of 1.5 mm is 0.46 mm, with a diameter of 50 mm - 3.35 mm. The drill shank and foot are used to secure the drill in the machine spindle or chuck. Drills can be made with or without a collar.

The diameter of the drill, measured by the ribbons, is not the same along the length of the drill. At the intake cone, it is slightly larger than at the shank. This reduces the friction of the ribbons on the walls of the hole.

In order to understand the device of the cutting part of the drill, consider the basic principles of operation of any cutting tool (including drills). One of the most important requirements for a cutting tool is that the chip to be separated is free to move away from the cutting point. The surface of the tool along which the chips run is called the front face. This face is tilted back at some angle from the vertical plane.

1 - wedge; 2 - processed object; γ (gamma) - front angle; α (alpha) - back angle; δ (delta) - cutting angle; β (beta) - taper angle.

Thanks to this angle, it is easier for the tool to plunge into the metal and the chips come off more freely along the front edge. The angle between the front face of the tool and a plane drawn perpendicular to the cutting surface is called the front angle and is denoted by the Greek beech γ.

The surface of the tool facing the part is called the back face. It is deflected at a certain angle from the surface of the workpiece to reduce the friction of the tool on the cutting surface. The angle between the back face of the tool and the cutting surface is called the clearance angle and denoted Greek letter α.

The angle between the front and back faces of the tool is called the angle of taper and is denoted by the Greek letter β.

The angle between the front face of the tool and the cutting surface is called the cutting angle and is denoted by the Greek letter δ. This angle is the sum of the taper angle β and the relief angle α.

The front and back angles are the angles that must be observed when sharpening.

Now let's find the edges and corners described above on the drill, which is not at all like the tool shown in the figure above. To do this, we cut the cutting part of the drill with the plane AB, perpendicular to its cutting edge.

The cutting edge is the line where the front and back edges of the tool intersect. The rake angle γ at the drill forms a helical groove. The angle of the groove to the drill axis determines the rake angle. The value of the angles γ and α along the cutting edge is variable, which will be discussed below.

The drill has two cutting edges interconnected by a jumper located at an angle ψ to the cutting edges.

Having received a general idea of the geometry of the cutting part of the drill, let's talk in more detail about its elements. The front face of the twist drill is a complex helical surface. Edge is a conventional name, since the word "edge" suggests a plane. The helical groove, the surface of which forms the front face, intersecting with the intake cone, creates straight cutting edges.

The angle of inclination of the helical groove to the axis of the drill is denoted by the Greek letter ω. The larger this angle, the larger the rake angle and the easier the chip flow. But the drill with an increase in the inclination of the helical groove is weakened. Therefore, for drills with a small diameter, having less strength, this angle is made smaller than for drills. large diameter. The helix angle also depends on the material of the drill. HSS drills can work in more stressful conditions than drills made of carbon steel. Therefore, for them, the angle ω can be larger.

The choice of the angle of inclination is influenced by the properties of the material being processed. The softer it is, the greater the angle of inclination. But this rule applies in production. At home, where one drill is used for processing different materials, the angle of inclination is usually related to the diameter of the drill and varies from 19 to 28° for drills with a diameter of 0.25 to 10 mm.

The shape of the flute should create enough room for the chips to be easily evacuated from the flute without weakening the drill too much. The groove width should be approximately equal to the nib width. The depth of the flute determines the thickness of the core of the drill. Strength depends on the thickness of the core. If the groove is made deeper, the chips will be better placed, but the drill will be loose. Therefore, the thickness of the core is chosen depending on the diameter of the drill. In small diameter drills, the core thickness is a larger fraction of the drill diameter than in large diameter drills. So, for drills with a diameter of 0.8-1 mm, the core width is 0.21-0.22 mm, and for drills with a diameter of 10 mm, the core width is 1.5 mm. In order to increase the strength of the drill, the thickness of the core is increased towards the shank.

The front edge of the drill is not re-sharpened.

The design of the helical grooves is such that as they approach from the edge of the drill to the center, their angle of inclination decreases, which means that the rake angle also decreases. The working conditions of the cutting edge at the center of the drill will be more difficult.

The back angle, like the front one, varies in magnitude in different points cutting edge. At points closer to outer surface drill, it is smaller, at points located closer to the center, more. The back angle is formed when sharpening the intake cone and is approximately 8-12 ° on the periphery of the drill, and 20-25 ° in the center.

The jumper (transverse edge) is located in the center of the drill and connects both cutting edges. The angle of inclination of the bridge to the cutting edges ψ can be from 40 to 60°. Most drills have ψ=55°. The jumper is formed by the intersection of two back faces. Its length depends on the thickness of the core of the drill. Since the thickness of the core increases towards the shank, the length of the web increases with each sharpening. In the process of drilling, the transverse edge only prevents the penetration of the drill into the metal. It does not cut, but scrapes or, rather, crushes the metal. No wonder it was once called the scraping blade. By cutting the web length in half, the feed force can be reduced by 25%. However, reducing the length of the bridge by reducing the thickness of the core will weaken the drill.

The angle at the top 2φ has a great influence on the operation of the drill. If the angle at the top is small, the chips with their lower edge will touch the wall of the hole and there will be no conditions for proper chip formation.

The figure below shows a drill with a normal taper angle.

The edge of the chip in this case fits well into the groove. Changing the corner angle changes the length of the cutting edge and, consequently, the load per unit of its length. With an increase in the angle at the top, the load per unit length of the cutting edge increases, while the resistance to the penetration of the drill into the metal in the feed direction increases. With a decrease in the angle at the top, the force required to rotate the drill increases, since the conditions for chip formation worsen and friction increases. But at the same time, the load per unit length of the cutting edge decreases, the thickness of the cut chips becomes smaller, and heat is better removed from the cutting edges.

Typically, the point angle (2φ) of standard universal drills made of carbon, chromium and HSS is 116-118° and is considered suitable for many materials. But in order to provide best conditions work, it is changed as shown in the table.

When using the content of this site, you need to put active links to this site, visible to users and search robots.

If we talk about those drills that are used by craftsmen at home, then their cost in stores is low. But even in this case, you should not use them as consumable for single use. After all, updating the drill to the best working condition will not be difficult if the master has the skill or special tools.

There are factory machines that are intended for sharpening, but this is a separate expense item, so most often craftsmen create such devices with their own hands.

Drills for metal create the most problems, and wooden blanks do not reduce the sharpness of the cutting edges so quickly.

To make a machine for restoring the sharpness of cutting elements, the necessary means of control (template), which is used to verify the tool.

Usually tools for ferrous metal, carbide bronze, steel or cast iron - with an edge angle of 115-125 degrees. The length of the other material, these parameters are different.

for soft bronze, red copper - 125, for brass alloys - 135;

for aluminum and soft aluminum alloys, granite, ceramics and wood - 135 degrees;

for magnesium and its alloys - 85 degrees;

for plastic, textolite and silumin - from 90 to 100 degrees.

Wizards, if necessary, make templates according to the above data. By the way, theoretically a single copy of the drill can be suitable for all these metals and other materials, if each time you sharpen different working surfaces.

An elementary handicraft fixture that is often used, bushings attached to the base. There are many drawings on the Internet for self-manufacturing. It should be noted that the tool must be well clamped, the accuracy depends on 1 degree.

If desired, you can make a significant size clip using aluminum or copper tubes correlative with the typical characteristics of drills or drill many holes in a soft metal workpiece. It is necessary that the sharpener has a comfortable hand rest to move the device and hold the stop.

This primitive sharpening machine is easy to install on a workbench or table.

Practical example of working with a drawing

The essence of the problem: there are drills, they need to be sharpened.
We will use one of the sharpening methods, close to the factory ones. Too lazy to catch hands. Better monkey way - put it and you're done. It took about 1 hour to make the fixture according to the finished drawing.

A little welding work by template. A corner has been made. Put on the puck, it's just pressed on.

Let's try the first sharpenings, if everything is assembled correctly, we will refine and cultivate, make a quick adaptation.

After sharpening the drill, we carry out a test. Two casting chips are visible, which means that the sharpening was carried out correctly.

The only drawback is that one chip is longer than the other, which means they missed the length of the edges. It is necessary to make an emphasis, which will regulate the length, ensure the symmetry of the edges. To do this, we will make a thrust washer, which will be exposed and machined. Or we cut it so that it becomes possible to process shorter drills.

Drills for metal are always hardened, but products can become dull over time. Naturally, this is not a reason to throw them out. If desired, you can sharpen the drill with your own hands, using professional equipment or home-made devices.

The main types of sharpening

Experienced craftsmen know that sharpening a drill for metal can be different. depending on diameter and application.

Single plane sharpening is designed for drills with a maximum diameter of 3 mm. In the process of doing the work, it is possible to “chunk” the edge, so you need to be very careful. To properly sharpen the product, it should be applied to the circle and moved parallel to the surface.
The tapered procedure is for larger metal cutting tools. In this case, the tool must be held with both hands, making sequential sharpening.
Finishing is performed after the end of sharpening. Thanks to this procedure, it is possible to grind the cutting edge and eliminate even the smallest notches.

To sharpen the drill with your own hands correctly, you must use the appropriate machines. Similar devices are divided into 2 groups.

If you are interested in the question of how to sharpen a drill for metal, then be sure to purchase the appropriate machine. For home use, an inexpensive model with medium power is suitable. It will allow you to sharpen small drills for metal.

Naturally, when buying pay attention to the noise level, as well as the design of the model. The best option will become a simple machine, because to choose for it the right details it will be easy.

It is necessary to buy such devices only in specialized places, since the kit provides for the presence technical passport. Moreover, you will be given a warranty card.

Use of machines at home

As mentioned earlier, at home it is advisable to use household machines. With their help, it is possible to sharpen various types of drills. It is important to remember that for some varieties you will have to buy the appropriate circles.

To sharpen the drill yourself, you should give preference to a machine equipped with a universal chuck. It allows you to clamp elements of various diameters.

The kit often comes with:

keys;
collets;
spare parts;
lamp for the working area.

The equipment from Drill Doctor and GS is the most popular. Similar products designed for sharpening drills with a diameter of 2–13 mm and 14–34 mm. Unfortunately, this equipment does not allow you to sharpen drills that are too thin. For this purpose, you will have to purchase a special machine.

All equipment designed for sharpening drills at home, has a number of advantages:

the ability to work from the mains;
high performance;
ease of use;
functionality;
sharpening accuracy;
affordable price;
compact dimensions;
light weight;
convenient control system, thanks to which you can adjust the intensity of sharpening and its speed.

Homemade sharpeners

If you do not have the appropriate machine, then you can sharpen using other devices. It is about an electric drill or homemade equipment, created according to the drawing. It is best to give preference to the second option, otherwise you can ruin a lot of drills before you master the correct sharpening.

You can create a suitable fixture with your own hands even from wood. So, a bar with holes corresponding to the diameter of the drills is fixed on a horizontal surface. The mentioned holes are made at a slight inclination to obtain the required sharpening angle.

Some masters prefer an electric drill equipped with the appropriate nozzles. Naturally, a small range of similar items, which complicates the sharpening with your own hands. As a rule, a stone and a leash are included with the nozzles. If you plan to sharpen drills using a specific drill, the leash should be shortened immediately.

If you wish, you can independently make a similar nozzle for a drill, guided by the recommendations given in the corresponding video. Such devices must be equipped with fasteners for fixing the drill.

Features of the sharpening process

If you first decided to sharpen a part with your own hands, do the work in a strict sequence.

First of all, the back surface is processed. So, the drill is pressed tightly and constantly monitored so that the sharpening angle remains the same. As a result of processing, the tip of the drill will resemble a regular cone.
Next comes the turn of the cutting part.
The last stage involves finishing the back surface. In this case, it is necessary to make sure that the size of the jumper is no more than 0.4 mm. Naturally, for a large drill for metal, this parameter should be slightly larger.

If something doesn't work out right the first time, don't despair. It is best to start practicing with tools that are unlikely to be needed. The main thing is to learn how to press and maintain the angle correctly. In this case, it is necessary to take into account the fact that the side parts of the drill, and not the tip, are responsible for drilling. Accordingly, the edges must be sharpened.

It is important to remember that in the process of sharpening small particles are formed. Because of the heat, they scatter in the form of sparks. It is for this reason that safety precautions must be followed. We are talking about the use of goggles and gloves. Also, when sharpening, make sure that the drill is securely fixed. Otherwise, it may accidentally slip out of your hands.

If you decide to use the appropriate machine for sharpening, be sure to prepare workplace. In particular, we are talking about good lighting. Also need wear protective gloves and goggles.

To properly sharpen the drill with your own hands, you need use a suitable device. It can be a household or industrial machine, as well as an electric drill with a special nozzle. If you have not tried to sharpen a drill before, first check out the corresponding video.

The technological process of mechanical processing of materials includes a wide variety of operations, which require high-quality and sharp tools. So, in a mechanical workshop at any machine-building enterprise, a set of turning, milling, drilling and more complex machines can be used. They use their own type of tool, for each of which there is a specific method of sharpening.

Features of the drills

Machining of metal is associated with huge loads on the tool. In general, it consists of three main parts: connecting, body and cutting. So the cutting part is a small wedge-shaped element designed to penetrate the metal and remove part of it from the workpiece.

If, for example, everything is clear in a turning tool or a disk cutter with the shape and design of the cutting part, then when processing holes on a drilling machine, everything is much more interesting and complicated, so you need to know how to sharpen the drill correctly. This is a tool designed for axial metal processing. That is, the feed movement is directed strictly along the axis. This should be considered before sharpening the drill for metal, because the wrong cutting angle will lead to vibration and breakage.

The main elements of the cutting part of the drill

Before sharpening a drill for metal, you should familiarize yourself with the design of its cutting part, which includes the following elements:

1. Main cutting edge.

2. Auxiliary helical cutting edge (ribbon).

3. Jumper.

4. Front surface.

5. Back surface.

What is needed for sharpening?

At the enterprise, everything necessary for the restoration of the instrument is always at hand. And here home master have to look for an alternative to high-quality factory fixtures in more simple solutions that can be used in a conventional garage. And yet, before sharpening a drill for metal, stock up on a minimum set:

1. Grinding wheel. It must be mounted on a rotating shaft. The device is popularly known as "emery". Very common in the garage.

2. Capacity for coolant.

3. Coolant (water or engine oil).

In order to withstand the angle of sharpening the drill, such a set may not be enough. After all, you will have to control the process "by eye", which is unlikely to work out without some experience. In this case, the basic kit also needs to include a tool for sharpening the drill, which you can buy or make yourself.

Controlled parameters

When everything is ready, it is necessary to familiarize yourself with some theory in order to have an idea about the main parameters of an axial cutting tool. Before you sharpen the drill correctly, you need to know its angles:

1. Front. Defined in the main cutting plane (running perpendicular to the main cutting edge) as the angle between the rake face and the main plane (perpendicular to the cutting speed vector). It is directed tangentially to the circle of the drill.

2. Rear. Also defined in the principal shear plane as the angle between the flank and the cutting plane (passes through the velocity vector and the cutting edge).

3. Corner at the top located between the two main cutting edges when viewed from the side of the drill.

The optimal value of the front angle is 18-20 degrees, the rear one is 10-12. The corner at the top in drills for metal has a standard value of 118 degrees.

Sharpening process

Now let's talk about how to sharpen a metal drill on ordinary sandpaper. The main sharpening of this axial tool is carried out on the rear surface. To do this, turn on the emery, firmly take the drill in your hand so that the main cutting edge is directed towards the rotation of the grindstone. Now we bring the edge to the grindstone, after which we turn the drill by the shank so that the cutting edge is parallel to the surface of the circle. We do the same operation with the second cutting edge. The result is the so-called simple sharpening drill, which is optimal for most metal processing modes.

Simple sharpening is used for drills with a diameter of up to 10 mm. By increasing this parameter, you can additionally perform a subpoint of the front surface. As a result, the rake angle decreases, which means that the thickness of the blade (the so-called cutting edge angle) and, accordingly, the drill life increases.

Sharpening with a fixture or machine

The method described above can be called artisanal, since it is simply impossible to achieve precise control of the drill parameters directly during sharpening. IN best case you will check the angles after the end of sharpening, and at worst, just check how much better the drill has become. And how to sharpen a drill?

Of course, for this it is better to use more advanced options that will allow you to tune in to certain angles in advance. In this case, you will need a device or machine for sharpening drills.

If the scale of work in your workshop is large enough, and regrinding of the tool is required constantly, then purchasing a machine will be optimal. It will greatly simplify the process, especially if you need to regrind carbide drills for metal. The main advantage of its use is the exact observance of predetermined parameters. At large volume work, it is unacceptable to use an incorrectly sharpened tool, as this will lead to a decrease in productivity. Modern grinding machines allow you to receive different types drill sharpening:

1. X-type. Mainly used for drilling in blind holes. Designed to reduce axial cutting force.

2. XR type. Used for universal drills. Cutting into the material is somewhat worse than in the first type, however, such drills have increased strength and durability.

3. S-type. The subpoint described above is used here, which also allows you to increase the life of the drill when machining. various materials(from cast iron to stainless steel).

4. N-type. A subpoint is also used, but of a smaller size. Drills with this sharpening are used for deep drilling.

Fixture design

As it has become clear, manual sharpening drills are the business of a professional who not only knows the right angles, but also feels the cutting process. Unfortunately, such a flair comes only after many years of practice with a drilling machine or drill. You should not experiment, as you can make your own or purchase a sharpening device. In both cases, it will include the same structural elements and work on the same principle.

So, the main task of the fixture is the correct orientation of the drill relative to the plane of the grinding wheel. To do this, its design includes a base plate, on which it is desirable to place both the device itself and the electric motor, on the shaft of which the grindstone is located. There is also a rotary column on the plate, on which the drill is fixed. It must be able not only to rotate, but also to move towards the grinding wheel.

As a column, you can use any bearing assembly with a shaft, for example, from an old drill. A drill bed is fitted on the shaft rings (you can use an adapter sleeve), to which it is pressed with screws. After fixing the drill, the grinder drive is turned on, the column is brought to the grinding surface and rotated to give the back surface of the drill correct form. It is important that during the initial setting of the fixture, the angle at the top of the drill is 118 degrees.

Sharpening nozzles

Another simple and convenient way involves the use of such a device as a nozzle for sharpening drills. Its main advantage lies in its versatility and ease of use. The device has a cylindrical shape. On the one hand, there is a connecting node, through which the nozzle is installed on the drill spindle. On the other side there are holes for installing drills of a certain diameter. For sharpening, the drill is inserted into the hole, after which the sharpening mechanism is driven by the drill motor.

Security measures

The sharpening of the drill is associated with the formation of small particles that break away from the sharpener during wear. They heat up and scatter in different directions in the form of fiery sparks, so for safety, you should use goggles and gloves.

When sharpening a drill without a tool, make sure to securely fix its position. Otherwise, upon contact with the sharpener, it can simply be pulled out of your hands.

Drilling metal or wood is a job that you do regularly. A high-quality nozzle does not require sharpening for a long time, but there are some errors in which blunting occurs ahead of time:

The use of a drill that does not match the material being processed. This does not necessarily mean drilling reinforced concrete with a wood drill, although in this case you will instantly turn cutting tool into a rod with a rounded end. For drilling various kinds metal and hard plastics, there are specially made drills. In case of discrepancy - the cutting edge quickly becomes unusable;
Wrong sharpening angle. This value must also correspond to the type of material in which the hole is made;
Overheat. The most common reason. When working with durable material, we want to quickly finish drilling, and we often forget about such trifles as cooling the work area. If it is not possible to ensure the supply of coolant to the tool, it is necessary to take breaks to cool the cutting edge. You can dip a hot drill into a container of water.

The mechanism of hot blunting is simple: The hot edge is “released”, that is, it loses its hardness. Cutting properties deteriorate, resulting in increased friction. Heating increases more strongly, and the process is aggravated in an arithmetic progression.

As a result, we may lose a good and possibly expensive tool. If you have on hand grinder for drills - the problem is solved on the spot, if not - you have to invent your own methods of sharpening.

Manual sharpening without tools

Locksmiths with extensive experience sharpen drills with their hands, using only a sharpener with a handy tool. But not all home masters can boast of such skills.

In addition, in this way it is possible to restore sharpness only to products of large diameter. Then it is easier to control the angle. The most popular size (3-5 mm) cannot be sharpened in this way. Even a template won't help here.

Craftsmen who regularly carry out drilling work will be interested in the variety of grinders for drills offered in power tool stores.

However, such devices (despite the obvious ease of use) are quite expensive. So the “home-made” run to the store for another Chinese tip. But home craftsmen with experience still use a tool from the times of the USSR, which corresponds to GOSTs in terms of strength and durability.

The secret is simple - many locksmiths of the old school have in stock homemade machine for sharpening.

IMPORTANT! For most household chores, you can get by with simple sharpening tools. Especially if the word "machine" scares you.

The simplest devices for dressing the cutting edge of the drill

To understand the process, take a look at constituent parts tip.

Then, by turning the bed, a plane (more precisely, a cone) of the backing is formed.

Sharpening is checked on the template and evaluated visually. All planes comply with the standard.

A guide is welded to the lower (rear) part of the corner bed to stop the drill shank. The emphasis itself is welded from the coupling and the corner.

Fixation is made with a screw. The stop is set to the limit value of the edge to be ground, and due to this, both cutting elements of the drill are ground symmetrically.

The sharpening of the working edge is made against the rotation of the emery wheel. In this case, the resulting burr is automatically removed by the running surface of the emery. For sharpening, two or three swings of the bed along the radius of the backing cone are sufficient.

This type of drill is sharpened along the outer surface of the emery stone, if necessary, use the lateral (radial) plane - the device can be turned to any angle.

The drill grinder is attached to the workbench with a clamp. You can fix the base permanently - but in this case, the possibility of fine adjustment will be lost.