We sharpen a drill at home - sharpening angle and other nuances. Sharpening a metal drill correctly How to sharpen metal
No matter how high-quality and expensive a drill is, its service life is not endless. However, it makes no sense to buy new components every time. You just need to figure out how to sharpen a drill to save yourself from unnecessary expenses. To do this, you can use an electric sharpener or, if it is not available, abrasive stone. You also need to know that twist and pobedit drills are sharpened in a slightly different sequence.
General information about self-sharpening drills
There are usually no problems with sharpening wood drills - they serve well, maintaining their original characteristics for many months and even years. With drills for metal or concrete, the situation is completely different - they must be sharp, use dull components to create holes in hard materials it is forbidden.
You can tell that it’s time to sharpen the drill by the appearance of a characteristic sharp creaking noise during the drilling process. It is not recommended to use dull products for work for the reason that in such conditions much more heat will be released, and this will contribute to even faster wear of the drill.
When studying information on how to sharpen a drill, you need to learn to understand not only the features of such work, but also know what equipment is used for this. The best option – special machine.
With absence industrial unit You can use a homemade power machine with an abrasive stone.
When choosing a sharpening technology, you need to take into account the shape that needs to be given to the back wall of the product. You can make one- and two-plane shapes, as well as screw, cylindrical and conical.
The drills are sharpened along the back edges. It is important that both nibs of the product are sharpened equally. Doing this manually is extremely difficult. In addition, creating the required shape and the required clearance angle solely by hand is also very difficult.
To work you will need:
- An electric sharpener or a special machine equipped with a diamond stone.
- Screwdrivers.
- Spanners.
- Wooden plank.
- Water for cooling.
A machine with a diamond stone is expensive equipment, and not everyone has access to such units. For use at home, you can assemble a homemade electric sharpener. An ordinary square board is suitable as a base. An engine with a power of 100-300 W and a rotation speed of 1500 rpm is installed on it. An abrasive wheel is fixed to the motor shaft. This easy-to-assemble device will allow you to sharpen your drill without any problems.
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The process of self-sharpening a twist drill
It was previously noted that sharpening can be single-plane or two-plane. For drills with single-plane sharpening, the back wall looks like one plane. The slope can be 28-30°. To sharpen such a drill, you simply need to place it on the abrasive wheel so that the cutting part runs parallel to it, and then begin the sharpening procedure. This simplest method Suitable for products with a diameter of no more than 3 mm.
For drills whose diameter exceeds 3 mm, it is better to use the conical sharpening method. Doing this manually without the appropriate skills is quite difficult, but can be done if desired. You need to take the drill with your left hand at the minimum possible distance to the fence cone. With your right hand, grab the product by the tail. The back wall and the cutting edge press the sharpened product against abrasive stone. By gently rocking the left hand on the back, a conical surface. In progress drill sharpening o There is no need to tear it away from the stone, movements should be smooth and relatively slow. The second feather is sharpened in the same order.
During the sharpening process, try to follow the original shape of the back of the product as much as possible to maintain the required back angles. This method is suitable for drill diameter up to 1 cm. If the diameter of the product exceeds 1 cm, it is necessary to sharpen it. The point of this procedure is that it is necessary to increase the slope cutting edge and reduce the rake angle. This increases the product's resistance to chipping, which increases its service life. The width of the cross section is reduced, making drilling much easier.
When working with drills with a small back angle, additional grinding of the back surface is performed. Thanks to this, it will rub the hole in the material less during the drilling process.
In production, after sharpening, finishing is usually carried out to remove small nicks and smooth the surface. Thanks to finishing, the wear resistance of the drill increases. If possible this processing It is recommended to do so. It is performed using round grinding stones made of silicon carbide on a bakelite bond.
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Step-by-step instructions for sharpening a Pobedit drill bit
The resource of Pobedit drills is also not eternal. After some time, such products also require sharpening. A dull drill will heat up too much during operation, make an unpleasant squealing sound and generally reduce the quality of drilling. For self-sharpening The same machine as in the previous instructions will do. Plain water is perfect for cooling. It is important to take into account the fact that sharpening a pobedite product can only be carried out using diamond stone, simple emery stones are not suitable for this.
Before starting work, make sure that it can be done; to do this, measure the height of the cutting part of the product: if the soldering height is about 1 cm, you can start sharpening.
The harder the metal, the slower the processing should be. The drill is sharpened with short touches of a diamond stone. As a rule, sharpening takes a little time, because... At its core, this procedure boils down to a small adjustment of the edges. Control each stage of work; it is important not to remove excess from the working part of the product.
The process of sharpening tipped drills is almost identical to the operation for small-diameter drills, i.e. The sharpening of the back is made flat. The drill is ground down to the soldering point.
It is also recommended to sharpen the front surface. If the soldering of the product has been ground down directly to the surface of the drill, sharpening is indispensable. Without it, the service life of the product itself and the quality of work will significantly decrease. The front surface is ground down so that the center of the soldering becomes thinner.
When performing each stage of work, you need to ensure that cutting sides the products were the same size. If this cannot be done, the displaced center will lead to a decrease in quality and disruption of the geometry of future holes.
Regardless of the unit used for sharpening, it is necessary to monitor the ratio of the rear and front angles of the cutting edge in relation to rotation. Another rule, especially relevant for sharpening drills for concrete: the higher the hardness of the material, the higher the sharpening angle should be. In the case of the winner, it should be equal to 170°.
The drill must not be allowed to overheat. This can lead to cracking and peeling of the carbide inserts. To prevent this, the drill must be cooled with liquid from time to time. Ordinary water is suitable for cooling.
Tools become unusable over time: they become dull, break and crack. Not all consequences of use can be eliminated, which is why you have to purchase new devices, but some can still be restored and given a second life. This is especially true for drills, which during use can not only break, but also become dull.
Types of metal drills
Today it is possible to make a hole in non-ferrous metals, steel, cast iron without the use of special equipment. For such purposes, you only need a high-quality drill and good drill bits.
This type of product comes in different shapes. For example, cutting tool in the form of a spiral, which is formed by several longitudinal grooves that remove chips. Such a device is usually called a spiral device.
Methods for sharpening drills for metal
Single-plane processing at home. This option is used when it is necessary to sharpen products no more than 3 mm.
The disadvantage of this sharpening is that the edge may chip during operation. This technique requires special care. Its essence is that the drill is applied to the circle and moves parallel to the working surface.
Sleeve or two-plane sharpening
This option is widely used by craftsmen to sharpen products. In this case, special bushings are used. First of all, you need to take left hand the drill by the working surface, then it should be brought to the intake cone, holding the device by the tail with your right hand.
The cutting edge of the product will be press against the butt grinding wheel and eventually a drill using right hand will begin to rotate around its own axis. In this way the back surface of the tool will be sharpened.
The main thing is to maintain the correct angle, formed between the end grinding stone and its tilt. It is for this purpose that special bushings are used to maintain the sharpening angle of the metal drill.
Conical sharpening
When you start sharpening twist drills with your own hands, first they process the back part, and then the cutting part. The work is carried out as follows:
Using attachments for sharpening metal drills
This convenient method involves using special devices for sharpening products. The advantages of this method include ease of use and versatility. This device has a cylindrical shape.
It contains, on the one hand, a connecting unit, with the help of which the attachment is put on the drill spindle, and on the other, there are recesses for installing drills of a certain width. To process it, you need to insert the product into the hole, after which all that remains is to set the device in motion with the drill motor and maintain the sharpening angle.
Finishing after sharpening the drill
Without finishing the product, it will not be possible to eliminate roughness and achieve smooth surface. In addition, drills subjected to finishing, gain wear resistance.
It is advisable to perform it with grinding wheels made made of green silicon carbide. When making adjustments, it is important to maintain the symmetry of the axes. To avoid mistakes, it is better to check correct sharpening of the drill angle with a template, which you can make yourself from the following materials:
- Aluminum.
- Copper.
- Steel.
Sheets of them should have a thickness of approximately 1 mm. Steel products are the most durable. Using the template, you can determine the length of the edges for cutting, as well as the angle between the jumper and the cutting part. It should be done before starting to use a new tool in order to transfer the required angles from the last one.
The easiest way to determine the correctness of the point is - carry out test drilling. When the cutting feathers are sharpened unevenly, in the less loaded part, chips will come out of the hole in small quantities. Sometimes it flies out through only one recess. Moreover, the diameter of the excavation made may exceed the thickness of the drill.
After sharpening a drill for metal, you need to pay attention to its symmetry. To make sure the work was done correctly, will be needed regular drill . Using this tool, they drill into plastic and then check which side will produce more chips. It is this facet that will need to be refined.
Rules for storing new and sharpened products
When carrying and storing metal drills, you must ensure that they do not rub against each other. Remember that when removing the device from the general box, the cutting working edges will become dull on adjacent products.
Therefore, it is better to make individual bushings or storage holes them in a vertical position. On top of that, it is recommended to sign the dimensions so that the search for the drill required size didn't take much time. Of course, it is necessary to control the humidity in the room to avoid corrosion of products.
Spiral products should be processed along the trailing edges. They should work out absolutely identical after work.
Moreover, doing this is not so easy, especially in manual mode, because it is necessary maintain a certain shape and angle tool while sharpening.
Before you start sharpening cutting tool, it is advisable to practice first on non-working products. It is also worth considering the fact that it is the side edges of the device that perform the drilling.
Sharpening is carried out to return the cutting part of the product to its factory shape. When working it's worth stick to the basic rule sharpening of tools with tips made of various alloys: the harder the material of the drill being processed, the lower the sharpening speed.
The more often a drill is used, the faster it becomes dull. Many craftsmen, as soon as a tool becomes dull, throw it away. And the practical ones process the product to a specific angle of sharpening the metal drill and continue to use it without any restrictions.
A metal drill is designed to create both blind and through holes and perforation in parts. As a rule, it has the shape of a spiral and consists of several elements: a cutting plane, a shank, a working part and a foot. The cutting tool is made from strong varieties high speed steel(P18,P6M5).
photo: metal drill design
The most important elements twist drill are shank and working surface. The shank is both cylindrical and conical shape provides reliable fastening to the cartridge. And along the edge of the working part, helical grooves are made to ensure the exit of chips.
The front side of the grooves rises up and moves back slightly, forming an angle, the magnitude of which varies in the direction from the axis to the side parts.
When making a twist drill, part of the material is removed from the outer working part, forming unique ribbons. Together with the increased diameter and increased angle at the tip of the drill, they help reduce friction between the tool and the walls of the future hole.
Types of sharpening drills for metal
Sharpening of drills is carried out with the aim of resuscitating tools after intensive use. There are several forms of sharpening. The choice in favor of a particular option depends on the diameter of the twist drill, the material being processed and other factors.
The normal sharpening shape at an angle of 118-120 degrees is considered universal. It allows you to select the drill angle that is optimal for any material. The only negative is that the drill diameter is limited to 12 millimeters. The options below apply to instruments with a diameter of up to 80 mm.
photo: metal drill sharpening angles
For example, the form of NP processing includes sharpening the transverse edge. Reducing the length helps reduce the force and, as a result, prevents unnecessary damage to the part being turned. Scope of application: preparing a drill for creating holes in steel.
A variation of this method is NLP. In addition to the described edge sharpening, a similar action is carried out with ribbons. As a result, an additional back angle of the drill is formed, which greatly facilitates the cutting process and reduces friction of the functional part when passing through the material being processed.
In some cases, double sharpening is also used. The DP, DLP and analogue methods are designed to improve the characteristics of the peripheral components of the drill. Changing the angular point between the edges to 75 degrees reduces heat dissipation from the drill and increases its durability.
Below is a table of metal drill sharpening angles for different types material.
An incorrectly selected drill sharpening angle leads to rapid heating, poor drilling and possible subsequent breakage of the drill.
The process of sharpening and checking the angle of a metal drill
The procedure is performed on a grinding wheel. The first stage is sharpening the back surface of the spiral. To do this, the tool is firmly pressed against the surface of the circle. Pay attention to stability - the sharpening angle of the drill for metal should be the same. As a result, if you look at the perk from the side, you should get the right cone.
Next, the cutting surface is processed. Here you should pay attention not only to the constancy of the angle, but also to the size of the jumper. For large gimlets, its size should not exceed one and a half millimeters.
The correct sharpening of the drill is checked using a template, which is made by hand by a craftsman or purchased from a factory. The drill test is based on the Reuleaux triangle, which is used to create cutting tools for creating square holes.
photo: template for checking the sharpening angle of the drill
It consists of three parts. The first side is used to control the cross edge, the second is the standard of the helix angle, the third measures the length of the cutting part and checks the apex angle. Quality work does not cause deviations - all parameters correspond to the lines of the template as they fit.
Metal drill sharpening angle: Video
A metal drill is the most common tool in any workshop, and proper sharpening of drills allows drilling to be done easily and quickly, even if the material being processed is quite hard. This article, more aimed at beginners, will describe almost everything related to the correct sharpening and finishing of a metal drill, as well as useful devices, which will significantly facilitate this operation.
Few people know that a twist drill is a more complex tool than a . And every self-respecting craftsman has a large number of twist drills in his arsenal different diameters and lengths and all of them will be useless if they are not sharpened correctly. This is especially important when drilling metals and, after all, drilling into wood, some kind of plastic, or other soft material perhaps with a dull drill, but with metals such a trick will not work.
In addition, a sharpened drill when drilling wood may not become dull enough for a long time, and when drilling metals and alloys, drills have to be constantly sharpened and kept in impeccable condition. Otherwise, when drilling with a blunt drill, you will have to exert a lot of force, but it will still be of no use and the tip of the drill will simply burn out. And anyone in general experienced master knows very well noticeable difference when drilling with a blunt and sharp drill.
A properly sharpened drill cuts perfectly into metals and alloys, even quite hard ones. But if the drill is used frequently, and the alloy is quite hard, then even a sharply sharpened drill will bite into the material more and more slowly every minute, and the pressure on the tool will have to be applied more and more.
The speed at which a sharpened twist drill becomes dull depends on several factors: the hardness or viscosity of the material being drilled, the feed rate (pressure force), the speed of the spindle or drill, the composition of the cutting fluid (coolant) used and other reasons and nuances.
And even if one of the above factors turns out to be unfavorable, then the sharpness of a twist drill is measured in minutes. Well, if you need to drill quite a lot of holes of the same diameter with one drill, and the material being processed is quite hard, then you will have to sharpen the drill quite often, otherwise the work will turn into torture, or you will have to make a supply of several new drills required diameter, and these are extra costs.
Therefore, every master who respects himself and his wallet should be able to sharpen twist drills correctly. But how to do this and with what help will be discussed in this article.
A creaking sound will indicate that the drill has begun to become dull; moreover, the force that needs to be applied to the tool increases in order for it to somehow continue to work. But it’s still better to stop working, otherwise the further you go, the greater the amount of heat generated, and the process of wear of the tool (its cutting edges) will be faster. In addition, the more the cutting edges (faces) of the drill wear out, the more difficult and longer it will take to restore them.
And the dulling process occurs from the very edges of the corners of the cutting edges of a twist drill, since the edges of the cutting edges not only bite into the material when drilling, but also experience friction from constant contact with the walls drilled hole. And the cutting speed at the edges is much higher than at the center. If you do not stop work in time to sharpen the drill, the dullness will gradually spread from the edges to the entire surface of the cutting edges and it will be more difficult to restore them.
Geometry of a twist drill.
Before moving directly to the correct sharpening of a drill, let’s consider what a twist drill consists of and its geometric parameters, since having become familiar with them, it will be much easier for beginners to sharpen drills correctly.
As mentioned above, a twist drill is quite complex instrument, even more difficult than a turning tool. As can be seen from Figure 1 a, a twist drill consists of a working part, a neck and a shank. The drill shank can be either conical - Morse taper, or cylindrical, and it all depends on the design of the spindle of the drilling machine or drill.
On the working part of the drill there are two helical (spiral - hence the name) grooves, which form two working feathers. Also, the working part of the drill has a cutting and cylindrical guide part with two spiral strips, which ensure the direction and centering of the drill in the hole being drilled.
The cutting part of the drill has two main cutting edges (see Figure 1), which are formed by the intersection of the rear and front surfaces, and the two main cutting edges perform the main work of cutting the material. Also, the cutting part has a transverse edge (see Figure 1 below right) on the drill bridge.
The drill neck is the intermediate part that connects the conical shank and the working part of the drill. The neck may be absent on small-diameter twist drills that have a conventional cylindrical shank.
Drill shank designed for fastening a drill in the spindle of a drilling machine or in a chuck of a machine tool or drill, and the shank also serves to transmit torque from the spindle (chuck) to the working part of the drill. As I noted just above, the shank can be either conical, for fastening in the conical hole of the spindle of a drilling machine or in an adapter conical sleeve with a Morse taper (I already wrote about this in a detailed article about drilling machines here). Or cylindrical, for mounting in a drill chuck.
The foot on the shank prevents the drill from turning in the conical hole of the spindle under heavy loads, and the foot also serves as a stop for knocking the drill out of conical hole spindle (knockout is done using a wedge).
Basic angles of a twist drill.
The main angles are shown in Figure 2.
The rake angle ϒ is measured in a plane that is perpendicular to the main cutting edge of the drill (this plane is indicated in Figure ΙΙ - ΙΙ). The angle ϒ is formed by the tangent line AM, indicated in Figure 2, to the rake surface at point A on the cutting edge and by the line AK, which is perpendicular to the cutting surface at the same point.
At different points of the cutting edge, the rake angle has different meanings. So if at the periphery on the outer diameter of the drill the angle has the greatest value of 20-30º, then when approaching the top of the drill it decreases to a value that is close to zero.
The clearance angle α is measured in a plane that is tangent to cylindrical surface, the axis of which coincides with the axis of the drill (the plane is indicated in Figure Ι - Ι). The clearance angle α is formed by the tangent to the clearance surface at point A on the cutting edge of the drill and the tangent at the same point to the cutting surface.
The clearance angles of a twist drill are different for different sections along the diameter of the drill. At the periphery, the rear angles are usually less than 6 - 8º, and at the jumper they can reach 30º.
Angle of inclination of the transverse edge ψ formed between the projections of the transverse edge (see Figure 1 b) and the main cutting edges on a plane that is perpendicular to the axis of the drill.
In order to increase the durability of a spiral drill (drills) with a diameter of more than 12 mm, double sharpening of drills is practiced and the cutting edges of the drill have the shape of a broken line (see Figure 3). In this case, the main angle 2φ is equal to 116º-118º - this is for cast iron and steel, and in section B, which is equal to 0.18 - 0.22 D mm. The second angle is still being sharpened at the tip of the drill 2φο - it is equal to 70 - 75º.
It should be noted that the durability with double sharpening of drills will be approximately twice as long as with conventional sharpening. This means that the cutting speed of spiral drills with double sharpening is approximately 15% higher than what is usually recommended in special tables of standards for drills with conventional sharpening.
Helical groove angle ω- this is the angle between the direction of the drill axis and the tangent to the drill strip. And the value of this angle is approximately from 18 to 30º. It should be noted that for spiral drills of small diameters (from 0.25 - 3 mm), the angle of inclination of the helical flute ω is made from 18 to 25º. Well, for spiral drills with a larger diameter (from 10 mm or more), the angle of inclination of the helical flute ω is 30º.
The angle at the tip of the drill 2φ is the angle that is enclosed between the cutting edges and, depending on the properties of the material being processed, it is advisable to take the following values of the angle 2φ:
- when drilling steel, cast iron and hard bronze, the 2φ angle is 116 - 118º.
- when drilling soft bronzes and brass, the angle 2φ is 130º.
- when drilling silumin, aluminum or babbitt, the angle 2φ is 140º.
- when drilling copper, the angle 2φ is 125º.
- when drilling celluloid, ebonite and other plastics, the 2φ angle is 85-90º.
And in order to reduce the effort during drilling and ensure the normal process of chip formation, two special points are used, which are shown in Table 2 below.
The first sharpening is the sharpening of the transverse edge of the drill and it is carried out on both sides to a length L.
The second point is the point of the drill strip at length L¹. In this case, the width of the ribbon is reduced to a size of approximately ƒ equal to 0.2 - 0.4 mm. And such a point reduces the friction of the ribbon on the walls of the hole being drilled.
Table 2 below provides data on the required angles and other elements when sharpening the drill(s).
Innovative (and not only) ways of sharpening drills.
Figure 4 shows the sharpening of a drill designed by V.I. Zhirov, which has a double sharpening and allows you to drill with fairly large feeds. In addition to double sharpening, this drill also has a strongly sharpened bridge and there is no transverse blade at all. This significantly reduces the axial forces and facilitates the process of cutting material during drilling.
Drill of Zhirov design
It is advisable to use such sharpening of a drill for drilling cast iron and other brittle materials, and when drilling them, the tool feed values are taken one and a half times larger than when drilling with drills with conventional sharpening.
Another innovative method of sharpening according to the method of E.Ya. Esinovich is shown in Figure 5. Quite a long time ago, back in the 60s of the last century, he began to cut two chip-separating grooves on the main cutting edges.
When drilling, these grooves perfectly crush chips and this makes it easier to remove chips from the hole (especially from a deep one) during drilling.
Drill designed by Esinovich
Also, with this sharpening method, the cooling conditions for the tool are significantly improved and all this increases labor productivity when drilling, especially when drilling deep holes.
Figure 6 shows sharpening a drill for drilling holes in the walls of pipes and in sheet material made of non-ferrous metal. If you drill pipe walls and sheet material ordinary drills, then inside the pipe or with reverse side steel sheet Quite large burrs are formed, which are quite problematic to remove in pipes (or in sills and other closed cavities of the car body).
Sharpening a drill for drilling holes in the walls of pipes made of non-ferrous metals.
And the drill shown in Figure 6 allows you to drill almost without burrs, since such a drill does not pull out burrs at the exit from the hole, but forms the remainder of the metal in the form of a thin washer using end A.
Also for high-quality drilling sheet material(for example, for holes in a car body when sharpening with a protruding tip, as well as for drilling various plastics, plywood, MDF, wood, the drill sharpening shown in Figure 7 is used. And as can be seen in Figure 7, the drill has sharp cutting edges of a concave radius ( radius R) and the curved edge has a profile depth h.
Sharpening a drill for drilling holes in sheet metal, plastic, plywood, wood...
And the ribbons are sharpened to a length L¹ and this length should be approximately 5 - 10 mm greater than the length of the hole that is being drilled. Well, the transverse edge is sharpened from the front surfaces at an angle of 10º.
When sharpening drills with a protruding tip (as in Figure 7b), the height of the protrusion h for drills with a diameter of 15 to 18 mm is approximately 3-4 mm, and the corners of the drill should protrude above the cavity by an amount h¹, which is equal to at least 1.8 mm.
Sharpening drills - the nuances of proper sharpening.
To begin with, it doesn’t hurt to remember for beginners that drills should be sharpened so that the transverse blade of the drill bridge is sharp and not rounded. Sharpening the drill is shown in Figure 8 and, as can be seen from the figure, sharpening is carried out along the rear surface.
And obtaining the required values of the geometry of a twist drill is based on the fact that the rear surfaces of the tool are parts conical surfaces imaginary cones, but the cutting edges of the drill must coincide with the generatrices of these cones. And the axes of the imaginary cones must be mutually perpendicular and make an angle β with the axis of the drill, which is equal to 45º.
When sharpening, the front end plane of the sharpening machine wheel (about sharpening machines and grinding wheels in detail) must coincide with the generatrix of an imaginary sharpening cone, the axis of which is the rotation axis of the sharpening machine head.
The twist drill being sharpened, clamped in the machine head at an angle β to its axis, makes a rocking motion around this axis during the sharpening process. And receiving different angles at the tip of the drill, 2φ is carried out due to a change in the angle at the tip of the sharpening cone (it follows from this that φ = α+β).
Well, if, for example, we turn the caliper with the axis of swing of the machine head located in it and set the angle α = 13º, then when sharpening the drill we get normal angle at the top, that is: 2φ=2α+2β=2×45º=116º.
And when sharpening, you should correctly clamp the drill in the cams of the machine head so that the drill is clamped exactly along the ribbons. And the distance ι from the peripheral points of the cutting edges of the drill to the clamping jaws (or jaws) should be selected according to Table 3, published below.
Sharpening the jumper and ribbon of a twist drill is usually done manually, using grinding wheel with slightly ground (rounded) edges. Well, as for the ones used abrasive wheels, then for sharpening drills made of high-speed and carbon steels, grinding wheels made of electrocorundum (ceramic bond) are used; the hardness of such wheels is CM1, and the grit size is from 63 to 80 - this is for pre-processing. For final processing, the grain size is of course smaller and ranges from 32 to 50.
Well, the correct sharpening is controlled using special templates, for example, as in Figure 9 (the figure shows checking the correct sharpening of drills using a template: a - to check the angle 2φ, b - to check the angle ψ).
Well, if you don’t have a specialized sharpening machine for sharpening drills, you can use the usual and simple device shown in Figure 10, in which the required angle for installing the drill is made (drilled).
Sharpening drills with a simple tool
That seems to be all, I hope many beginners will find something useful for themselves in this article and sharpening drills will no longer be the same for them complex operation, good luck to everyone.
Technological process machining materials includes many different operations, which require high-quality and sharp tools. Thus, in a machine shop 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, each of which has a specific sharpening method.
Features of drills
Mechanical processing of metal involves enormous 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, in a turning tool or disk cutter While everything is clear with the shape and design of the cutting part, 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 taken into account before sharpening a drill for metal, because an incorrect cutting angle will lead to vibration and breakage.
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 will you need for sharpening?
At the enterprise, everything necessary for instrument restoration is always at hand. And here home handyman we have to look for an alternative to high-quality factory devices in more simple solutions, which can be used in a regular garage. And yet, before sharpening a drill for metal, stock up on the minimum set:
1. Grinding wheel. It must be installed on a rotating shaft. The device is popularly known as “emery”. It is very common in the garage.
2. Coolant container.
3. Coolant (water or engine oil).
In order to maintain the sharpening angle of the drill, such a set may not be enough. After all, you will have to control the process “by eye,” which is unlikely to happen without some experience. In this case, the basic kit must also include a device 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 of the basic parameters of an axial cutting tool. Before you sharpen a drill correctly, you need to know its angles:
1. Front. Defined in the main cutting plane (runs perpendicular to the main cutting edge) as the angle between the rake surface and the main plane (perpendicular to the cutting speed vector). It is directed tangentially to the drill circumference.
2. Rear. Also defined in the main cutting plane as the angle between the flank surface and the cutting plane (passes through the velocity vector and the cutting edge).
3. Apex angle located between the two main cutting edges when looking at the drill from the side.
The optimal value of the front angle is 18-20 degrees, the rear angle is 10-12. The tip angle in metal drills has a standard value of 118 degrees.
Sharpening process
Now let's talk about how to sharpen a metal drill using regular sandpaper. The main sharpening of this axial tool is carried out along the rear surface. To do this, turn on the emery, firmly grasp the drill in your hand so that the main cutting edge is directed towards the rotation of the sharpener. Now we bring the edge to the sharpener, after which we turn the drill by the shank so that the cutting edge is parallel to the surface of the circle. We perform 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 sharpen the front surface. As a result, the rake angle decreases, which means the thickness of the blade (the so-called cutting edge angle) increases and, accordingly, the service life of the drill.
Sharpening using a jig or machine
The method described above can be called artisanal, since precise control of the drill parameters directly during sharpening is simply impossible to achieve. In the best case, you will check the angles after finishing sharpening, and in the worst case, you will simply check how much better the drill has become. How to sharpen a drill correctly?
Of course, for this it is better to use more advanced options that will allow you to adjust 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 tool sharpening is required constantly, then purchasing a machine would be optimal. It will significantly simplify the process, especially if you need to resharpen carbide drills for metal. The main advantage of its use is the exact adherence to predetermined parameters. When there is a large volume of work, it is unacceptable to use an incorrectly sharpened tool, as this will lead to a decrease in productivity. Modern sharpening machines allow you to receive Various types drill sharpening:
1. X-type. Mainly used for drilling blind holes. Designed to reduce axial cutting force.
2. XR type. Used for universal drills. The penetration into the material is somewhat worse than in the first type, however, such drills have increased strength and durability.
3. S-type. The point described above is used here, which also allows you to increase the service life of the drill during processing various materials(from cast iron to stainless steel).
4. N-type. A point is also used, but of a smaller size. Drills with this sharpening are used for deep drilling.
Device design
As has already become clear, manual sharpening drills are the work of a professional who not only knows the correct angles, but also feels the cutting process. Unfortunately, such an instinct comes only after many years of practice working with a drill press or drill. There is no need to experiment, as you can make it yourself or purchase a sharpening device. In both cases it will include the same structural elements and work according to the same principle.
So, the main task of the device 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 sharpener is located. The plate also contains a rotary column on which the drill is fixed. It must be able not only to rotate, but also to move towards the grinding wheel.
Any bearing assembly with a shaft can be used as a column, for example from old drill. A drill bed is fitted onto the shaft rings (you can use an adapter sleeve), to which it is pressed with screws. After fixing the drill, the sharpener drive is turned on, the column is brought to the grinding surface and rotated to shape the back surface of the drill correct form. It is important that when initially setting up the device, the drill tip angle is maintained at 118 degrees.
Sharpening with attachments
Another simple one convenient way involves the use of a device such as a drill sharpening attachment. Its main advantage is its versatility and ease of use. The device has cylindrical shape. On one side there is a connecting unit, through which the attachment is installed on the drill spindle. On the other side there are holes for installing drills of a certain diameter. To sharpen, the drill is inserted into the hole, after which the sharpening mechanism is driven by the drill motor.
Security measures
Drill sharpening is associated with the formation fine particles, which come off the sharpener during wear. They heat up and fly in different directions in the form of fiery sparks, so for safety you should use safety glasses and gloves.
When sharpening a drill without a jig, make sure to securely fix its position. Otherwise, upon contact with the sharpener, it may simply be torn out of your hands.
