How to make a device for sharpening drills. Device for manual sharpening of twist drills. Some time ago, I accidentally came across (meaning the author of the article, see source) on the Internet some very useful video tutorials by V. Leontyev on manual sharpening of twist drills:

But then an idea arose on how to make sharpening drills even simpler and more convenient. As a result of thought and experimentation, the device described below appeared. First, it was necessary to modernize - to bring to mind the existing factory-made Chinese (like German) sharpener. Because it was almost impossible to work with him using V. Leontiev’s techniques.

Electric sharpener made in China.

Flimsy standard support bracket.

The design of the tool rest is unsuitable for work.

Firstly, the bracket for attaching the hand rest to the disc casing is too flimsy, made of metal 2 mm thick. It bends with a little effort. Therefore, naturally, the sharpening angles are +/- kilometer! And the shape of the tool rest absolutely does not allow making a normal back angle according to V. Leontiev’s method, since the drill, when lowering the shank, rests against the corner of the bracket. Moreover, the hand rest itself is installed BELOW the axis of the disk. That is, there is no way to get a normal clearance angle at all, unless you use the end surface of the disk.

The plane of the tool rest is much lower than the axis of rotation of the disk.

New support bracket.

For a normal bracket, a piece of metal 4 mm thick was used, bigger size and additional mounting screws. The old bracket was secured with two rivets that had to be cut off. Now the new bracket is much stiffer than before. Also, a horizontal shelf of the tool rest with additional mounting holes was welded from pieces of angle and strip. Its position can be adjusted within certain limits.

Comparison of metal thickness in new and old tool rests.

The new bracket is attached at 5 points.

Device details. Bracket. Handyman. Rotating plate...

Next, the device itself was manufactured. It is a rotating plate with a welded bushing, which can swing on an axis fixed in the eye, which in turn is attached to the tool rest. A guide plate for drills, in which a triangular groove is selected, is attached to the rotating plate on top.

The device is assembled. The plate is in a horizontal position.

The device is assembled.

Sharpening device.

At first, instead of this plate, a guide in the form of a piece of a corner was tested (as in V. Leontiev’s video), but this option is not suitable at all - the drill is difficult to fix properly (it tries to run to the right when it touches the disk), especially since it is also required push forward when forming the rear corner. In general, the corner (it is in the photo) is completely unsuitable.

The device is in the down position.

Working with the device resembles the movements of the author of video tutorials, only instead of a finger and an eye, a swing axis and set angle drill sharpening. It is much more convenient with the device to control the parallelism of the drill cutting edge being processed to the disk. You just need to turn the plate down and press the drill into the groove so that the line of the cutting edge is parallel to the plane of the plate - the axis of swing of the plate. This moment is shown in the photo.

Installing the drill on the tool rest to the whetstone.

First, the edge itself is formed. When processing the rear corner, it is necessary to simultaneously lower the plate down and move the drill itself forward towards the disk. You must try to prevent the drill from rotating around its axis when shaping the edge and processing the back corner. I control the symmetry of the edges in the same way as in the video tutorials. By the way, instead of a swinging plate, you can install a piece of an angle with fixed sharpening and back angles on the tool rest - this is for sharpening carbide drills. It is only necessary to determine locally the required length of the sides of the angle to obtain the desired rear sharpening angle, since it also depends on the diameter of the disk and the location of the tool rest relative to the axis of rotation of the disk.

Installing the drill into the guide groove of the plate.

Control of drill installation. The cutting edge of the drill is parallel to the surface of the insert.

Guide groove configuration.

Device for manual sharpening of twist drills.

Then you won’t have to contact a specialist every time, and you yourself will be able to maintain the desired sharpness of the drill.

For sharpening it is necessary special device which is used in professional work.

However, if you don't have one, you can assemble the sharpening device by hand and do all the work yourself correctly.

From the article you will learn how to make a machine necessary for sharpening metal, as well as how to properly sharpen a drill for metal. The instructions in the video will help you cope with this work faster and do everything correctly. You will also learn how to sharpen core, step and other types of drills.

Preparing for work

You don't have to be a professional to know how to sharpen metal drill bits. This requires a sharp tool to help keep it in optimal working condition.

Since you have to sharpen a metal device regularly, if you often work with this tool, some people prefer to buy a ready-made sharpening machine rather than assemble it themselves.

The most effective adaptation for sharpening core drills - a machine on which a sharpening stone is installed.

It's very easy to use and you won't need complex instructions to get started.

However, it is advisable to know some of the nuances of how sharpening is carried out before starting the process: the tool is processed from behind along the edges, and the most important role is played by the angle at which the tool is positioned when fed to the machine.

If the angle is incorrect, the tool will be damaged and it will be impossible to correct it - you will have to buy a new one.

During sharpening, the greatest attention should be paid to the edge that makes up the cutting part of the device - it should be the sharpest, since it interacts with metal parts: screws, jumpers, etc.

Watch a video on how to properly sharpen your jigs before you begin this process yourself.

After this you need to collect necessary tools that you will need to do grinder. You won’t be able to make it from improvised means - you’ll have to visit a hardware store.

First of all, you will need special wheels that are needed for sharpening.

You will only need to install one circle on the device itself, but they quickly become unusable, so it is recommended to buy several parts at once, so as not to spend a lot of time replacing them later.

This is especially true if you use the tool constantly - then you will have to sharpen it often. The purchased circle is installed on a rotating shaft.

In addition to these parts, you will need a cooling liquid - this can be water or machine oil. You also need a container into which the liquid will be poured.

If you do everything yourself, then you must remember about the liquid, because during the sharpening process the tool becomes very hot.

If you cannot cool it, its properties will deteriorate, and each time it will fail faster and faster.

A homemade hole saw must have the correct angle, and this is the most difficult part of making a DIY device.

To make the angle correct, you need to make difficult calculations, so consumers often decide to purchase a ready-made sharpening tool to save time and effort.

The most important angle is at the front, it is determined based on the main cutting plane.

The rear angle has parameters similar to the front one, but in accordance with the rear plane.

In order to determine how the top corner is located, you need to look at the device from a side position: in the correct position, it is located between the first and second edges.

Typically the first angle should be about 20 degrees and the back angle 10 degrees. Top corner always has the same value on all devices: 118 degrees.

Before work, you need to prepare gloves and goggles, since this work can be traumatic.

If you have little experience in creating such machines with your own hands, then pay more attention to how the circle is positioned, because if its feed angle is incorrect, the circle will simply break out of your hands.

Watch a video on how to assemble a sharpening machine - it will be very helpful if you have little experience.

The sharpening process and advantages of the machine

Core, step and other drills are sharpened in the same way, in several stages. The back of the device will be most involved.

First you need to turn on the device equipped with emery and bring a stepped drill to the circle, for example, which needs to be sharpened. In this case, the cutting part of the stepped drill should be directed towards the sharpener.

When working, the drill must be held very tightly so that it does not slip out.

If you positioned the drill correctly, it should be parallel to the mechanism.

In this position, all that remains is to sharpen it, and then you will get quality tool, which can be used again.

This sharpening method is only suitable for small drills, the diameter of which does not exceed 10 mm.

If the diameter of the drill turns out to be larger, then you need to extend the time spent on sharpening, and also pay more attention to the front side of the tool.

How to sharpen drills with different diameters, look at the video.

To sharpen core drills with a diameter of more than 16 mm, you will need a full-fledged machine.

In this case, doing it yourself will be more expensive and longer, but using a machine will make it better quality, since in this case you can easily set the correct inclined angle.

If you use drills frequently different sizes, then the machine will quickly pay for itself, because they have to be sharpened constantly.

There are several characteristics of core drills and other drills that can only be sharpened using a machine. Read them before you start working.

Firstly, if a stepped or other device is designed to work with a blind hole where the axial cutting force is reduced, then such a tool must be sharpened on a machine.

This is also the case with drills designed to work with durable metals, or with tools that have a small point and are designed for drilling deep holes.

A proper straightening machine must not only sharpen the drill, but also orient the tool towards the surface being processed relative to the grinding wheel.

That is why the machine is equipped with a sharpening plate that allows you to do this.

The device itself is fixed on the grinding plate, as well as the shaft and motor, thanks to which the machine is started.

The machine drill is installed on a rotary column, which is also located on the base plate.

The stove is easy to rotate the way you need and conveniently - this is another plus in using a full-fledged device.

The machine is started using a motor, so the column can be made from any bearing unit equipped with a shaft.

You will need to attach a mount to the shaft where the sharpening drill will be installed. You can fix it with ordinary bolts - they will give the tool the necessary reliability.

After you have installed the drill, you can turn on the machine: after starting, the column will automatically approach the circle and turn it around with the back part that needs sharpening.

This system is very convenient because it allows you to independently set the angle required for high-quality processing of the tool.

Large machines are used for processing twist, core and other drills that have a diameter of more than 16 mm, for more small tools Compact packing machines can be used.

It is more convenient to work with such devices, because they can be moved or installed where you need them.

The design of such a machine is similar: on one side there is a connection unit responsible for installing the drill on the spindle, and on the other there is a hole into which the drill is installed.

Working with this device with your own hands is much easier: you need to fix the drill all the way, and then start the machine.

The simplest, but the least effective method sharpening a tool - do it with a grinder, or with a device on which a movable wheel is installed.

This method can only be effective if you manage to fix the drill in the correct position, which is quite difficult.

This method is dangerous because during operation the drill can easily slip off the wheel.

It makes sense to use a grinder only if you need to machine a drill with a minimum diameter, and there are no other devices for this.

In addition, sharpening with a grinder does not imply the creation of finishing, which is a very important part of the process. Finishing is needed to make the tool even and smooth.

When professionally sharpening, finishing is required, as this increases the service life of the device.

If you have a silicon carbide wheel, then the finishing process can be done with your own hands at home.

Despite the fact that the process of sharpening a drill is not too complicated, without specialized devices, although it is not recommended to do this with your own hands, because you can not only damage the tool, but also injure yourself if you do not follow the working technology, or use tools not intended for sharpening, for example, a grinder.

If you only have to drill into wood, then you don’t have to worry about the sharpness of the drill, since the drill can serve well 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 bit. You can easily feel the difference when you take a completely new drill. Having started to cut into the metal rather quickly, with every minute the drill will plunge into the metal more and more slowly, and you will have to press on it more and more. The rate of dulling of a drill depends, in particular, on revolutions, feed rate, cooling and other factors, but no matter how hard you try, the time it takes for a drill to become unsatisfactory 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, therefore, the heating of the cutting edges is maximum. At the same time, heat removal from the corner of the cutting edge is very difficult. Therefore, dullness begins from the corner, then spreads throughout cutting edge. Its curve is clearly visible. Then the back edge wears off. Strokes and marks appear on it, coming from the cutting edge. As they wear, the marks 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 becomes wrinkled when worn.

At the beginning of dulling, 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 proceed faster.

To make it easier to control the geometry of the drill, the main thing that should be done is the template described below. With its help, even if sharpening is carried out without tools, you can always check where else the metal needs to be removed, and, in the end, get what you should get (it’s impossible that it won’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 and pressure constant for each section.

Sharpening twist drills

The drill is sharpened along its rear edges. It is very important that both blades (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 back angle (see below for which angle).

There are special machines or devices for sharpening. If possible, it is better to sharpen drills using specialized equipment. But in a home workshop, such an opportunity, as a rule, does not exist. Drills have to be sharpened by hand using an ordinary sharpener.

Depending on the shape of the back surface, there are different types of sharpening: single-plane, double-plane, conical, cylindrical, screw.

With single-plane sharpening, the back surface of the pen is made in the form of a plane. The clearance angle for such sharpening should be 28-30°. With single-plane sharpening, there is a high risk of chipping the cutting edges. This method, which is the easiest to carry out by hand sharpening, is recommended for drill diameter up to 3 mm.

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

Let's imagine a cone, the generatrix of which is directed along the cutting edge and the end of the grinding wheel, and the apex is 1.9 times the diameter of the drill. The apex angle is 26°. The drill axis 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 a cone along the end of a grinding wheel), then a conical surface. If the axis of the drill and the axis of the imaginary cone are in the same plane, then the clearance angle will be zero. To form a back angle, you need to shift the axis of the drill relative to the axis of the 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 this mixture will provide a conical back face and a back angle of 12-14°. The larger the offset value, the larger the relief angle will be. It should be remembered that the clearance 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 sharpening conditions manually. The drill intended for sharpening is taken by the working part with the left hand, possibly closer to the intake cone, and by the tail with the right hand.

The cutting edge and rear surface of the drill are 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, rock it, creating a conical surface on the back edge of the pen. Then repeat the same procedure for the second feather.

When sharpening, it is advisable 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. The cutting edge of the drill is pressed against the end of the grinding wheel and with a smooth movement of the right hand, without lifting the drill from the stone, rotate it around its axis, sharpening the back surface. It is very important to maintain when rotating the drill desired angle its inclination to the end of the grinding wheel. For this purpose, special bushings are often used when sharpening.

As a result of this sharpening, a tapered surface will be formed 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, therefore, the heating will be greater.

Due to friction with the grinding wheel, the tool heats up during sharpening. This causes the hardened part of the tool to temper. The metal softens and loses its hardness. Inept sharpening renders the tool blade 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 any reason the tool is sharpened dry, then:

• a small layer of metal is removed in one pass;
• the rotation speed of the abrasive wheel should be as low as possible;
• The drill should never become so hot that the hand cannot tolerate it.

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

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

In production, sharpening is usually followed by finishing. Finishing makes the surface smoother and removes small nicks. A polished drill is more resistant to wear than a drill after sharpening. If you have the opportunity to do some fine-tuning, take it.

For finishing, grinding wheels made of green silicon carbide grade 63C, grit 5-6, hardness M3-SM1 on a bakelite bond, or wheels made of CBN LO, grit 6-8 on a bakelite bond, are used.

One of the main conditions for correct sharpening of a drill is maintaining its axial symmetry. Both cutting edges must be straight and have identical lengths and identical apex angles (and point angles) relative to the drill axis.

The correctness of sharpening is checked with a special template.

a - template; b - checking the angle at the apex and the lengths of the cutting edges; c - sharpening angle; g - 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 is, of course, made of steel. The template is used to check the angle at the apex, the length of the cutting edges, and the angle between the jumper and the cutting edge. Instead of the back angle, which is very difficult to measure, the tip angle is measured using a template. It is advisable to make a template before using a new drill in order to transfer the required angles from the last one.

The uneven length of the cutting edges and their inclination to the axis of the drill also lead to unequal load. The drill will fail faster due to 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 - cutting edges are sharpened to different angles to the axis of the drill, the middle of the jumper coincides with the axis of the drill.

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

The easiest way to check the correct sharpening is test drilling. If the drill feathers are sharpened unequally, then the less loaded one will have less chips from the corresponding groove. Sometimes chips protrude through only one groove. 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 it is sewn (nailed, glued) at an angle of 30-32° (depending on the angle 2φ, see below, 30° for 2φ=120°, 32° for 2φ=116°) ) wooden slats with a side edge beveled at an angle of 25-30° (for single-plane sharpening). This rack orients the holder with the drill being sharpened at the desired 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 edge of the rail). With this sidewall, the holder is pressed against the rail on the base board, which ensures sharpening of the front angle of the drill within the required limits (25-30°). On the other sidewall of the holder, mark and drill through holes perpendicular to the plane of this sidewall for each drill of one diameter or another. The length of the holder is chosen so that it is comfortable to hold when sharpening drills.

You cannot install the device on a regular pad (armrest), so you will have to come up with some kind of table or shelf for it; you can move the sharpening machine to a table where there will be room for this device. Place a holder with a drill inserted into it to be sharpened, close to the rail, on the base. Turn the drill in the holder socket so that the sharpened edge is oriented horizontally. With your left hand, hold the drill near the edge to be sharpened, and with your right hand, hold the drill shank. While pressing the holder against the beveled strip, move the drill to the emery wheel and sharpen one edge. Then turn the drill and process the second edge in the same way.

It can be done even simpler:

Sharpening angles and other characteristics of the drill

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

A twist drill consists of a working part, a neck, a shank and a claw.

A - with a conical shank; B - with a cylindrical shank; a - working cutting part; b - neck; in - width of the pen; g - foot; d - leash; e - screw flute; f - feather; z - shank; and - jumper; L - total length; L 0 - length of the “working cutting part”; D - diameter; ω - angle of inclination of the “chip screw groove”; 2φ - apex angle; f - width of the spiral ribbon; ψ is 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 to guide during cutting and is a spare part when resharpening the drill. On the feathers of the guide part along the helical line there are cylindrical chamfers-ribbons. The ribbon serves to guide the drill in the hole, as well as to reduce friction of the drill on the walls of the hole. It shouldn't be wide. Thus, the width of the drill strip with a diameter of 1.5 mm is 0.46 mm, and 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 neck.

The diameter of the drill, measured by the strips, 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 against the walls of the hole.

In order to understand the structure of the cutting part of the drill, we will consider the basic principles of operation of any cutting tool (including the drill). One of the most important requirements for cutting tool is to ensure that the separated chips move freely from the cutting site. The surface of the tool along which the chips run is called the rake face. This face is deflected back at a certain angle from the vertical plane.

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

Thanks to this angle, it is easier for the tool to cut into the metal and the chips flow more freely along the front edge. The angle between the front edge of the tool and a plane drawn perpendicular to the cutting surface is called the rake 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 rear edge of the tool and the cutting surface is called the clearance angle and is denoted by the Greek letter α.

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

The angle between the front edge 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 tip angle β and the relief angle α.

The rake and back angles are the angles that must be maintained when sharpening.

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

The cutting edge is the line of intersection of the front and rear edges of the tool. The rake angle γ of the drill is formed by a helical groove. The angle of inclination of the groove to the drill axis determines the size of the rake angle. The magnitude of the angles γ and α along the cutting edge is variable, as will be discussed below.

The drill has two cutting edges connected to each other by a bridge located at an angle ψ to the cutting edges.

Having received general idea about the geometry of the cutting part of the drill, let's talk in more detail about its elements. The front edge of a twist drill is a complex helical surface. Facet is a conditional name, since the word “facet” implies a plane. The helical flute, the surface of which forms the leading edge, intersecting with the chamfer, creates straight cutting edges.

The angle of inclination of the helical groove to the drill axis is denoted by the Greek letter ω. The larger this angle, the larger the rake angle and the easier the chip exit. But the drill weakens as the inclination of the helical flute increases. Therefore, for drills with a small diameter, which have less strength, this angle is made smaller than for drills large diameter. The angle of inclination of the helical flute also depends on the material of the drill. High speed steel drills can operate under more stressful conditions than carbon steel drills. Therefore, for them the angle ω may be larger.

The choice of inclination angle is influenced by the properties of the material being processed. The softer it is, the greater the angle of inclination can be. But this rule applies in production. At home, where one drill is used for processing different materials, the inclination angle is usually related to the drill diameter 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 space to accommodate chips and allow them to be easily removed from the flute, but not weaken the drill too much. The width of the groove should be approximately equal to the width of the pen. The depth of the groove determines the thickness of the drill core. Strength depends on the thickness of the core. If the groove is made deeper, the chips will be better accommodated, but the drill will be weakened. 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 proportion 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 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, and therefore the rake angle decreases. The working conditions of the cutting edge near the center of the drill will be more difficult.

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

The bridge (transverse edge) is located in the center of the drill and connects both cutting edges. The angle of inclination of the jumper to the cutting edges ψ can be from 40 to 60°. Most drills have ψ=55°. The bridge is formed by the intersection of two back faces. Its length depends on the thickness of the drill core. As the thickness of the core increases towards the shank, the length of the bridge increases with each sharpening. During the drilling process, the transverse edge only interferes with 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 a scraping blade. By halving the length of the bridge, 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 tip angle of 2φ has a great influence on the operation of the drill. If the apex angle is small, the lower edge of the chip will touch the wall of the hole and there will be no conditions for proper chip formation.

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

In this case, the edge of the chip fits well into the groove. Changing the tip angle changes the length of the cutting edge and therefore the load per unit length. As the tip angle increases, the load per unit length of the cutting edge increases, and the resistance to penetration of the drill into the metal in the feed direction increases. As the tip angle decreases, the force required to rotate the drill increases, as 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 high speed steel is 116-118° and is considered suitable for many materials. But in order to ensure 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.

Drills must be of high quality and well sharpened in work professional master. In the old days, drill sharpening was done by hand.

Today there are special devices for sharpening drills, and their design is very simple.

Why is sharpening needed?

If the drill becomes dull, it is very difficult, and sometimes impossible, for them to drill through the surface. It is also worth noting that for different types drill surfaces must have a certain sharpening angle, for example, for a plastic surface the angle will be 30 degrees, for hardened steel this angle will be 130 degrees.

In cases where a perfectly drilled hole is not required, the sharpening angle can be 90 degrees.

How to properly sharpen a drill

You can sharpen the drill yourself using abrasive discs. During sharpening, the drill must be held by work surface. You need to hold the tail of the drill with your other hand.

From the side, the drill must be pressed against the abrasive disc. Then it is advisable to turn it with extreme care, as a result the cutting edge will take the required angle and structure.

Sharpening the drill must be done on each side separately. It is also necessary to ensure that the tip of the drill is located exactly in the center when sharpening the cutting part. This must be done correctly, as an error in sharpening can cause the drill to skewer to the side.

Drill sharpening but with your own hands not the best good way, since it is capable of carrying with it a number of inaccuracies, for example, the cutting edges may not be correct in relation to the tool axis.

Sharpening device

The device is designed for sharpening blind or through drills made of cast iron and steel. This device is made taking into account the types of sharpening, as well as its size. It is easy to change the sharpening angle on the machine.

There are two types of devices that will help sharpen a drill: a household and an industrial machine. In the first case, the sharpening device takes up little space and fits perfectly into the home, but such a machine can only sharpen small drills.

Industrial machines that are made to sharpen drills with large diameters have great power. The industrial machine has a clamp and a sharpening wheel.

With this device, drill sharpening occurs under the supervision of an operator who can easily control the process. Such devices are designed for long-term operation.

How to make a machine for sharpening drills with your own hands

We will need following materials: abrasive disc, switch, motor with good power, stand, wires, axle and plug. Also, for the safe use of the machine, it must have a housing, outside of which it is necessary to place an axis with an abrasive wheel for operation.

You first need to decide on the installation location of the machine, since it will be connected to an outlet.

Also, our device should be placed on a table, preferably made of metal, where the engine will need to be placed, and marks should be placed for making holes for the bolts.

An abrasive disc is placed on the motor shaft. To secure it to the shaft, you must first put on the washer, then the disk, and then the washer again. After this, you should install the fastening nut on the pre-prepared thread on the shaft.

An engine from washing machine. The power of its motor will be sufficient for the process of sharpening drills. Wires can also be taken from improvised equipment.

Note!

You need to connect the wires to the starter, which should have three open contacts. The winding must be capable of connecting phase lines using two starters connected in series.

The off button should be connected to NC, and the start button will be connected to NO, and it should also be in parallel connection with two NO contacts of the starter.

When you press the power button, voltage will be applied to the winding and as a result the circuits should close. When the button is released, the voltage supplied to the starter should not be removed. When disconnected, the engine must stop.

The engine itself is a safe device, but to protect its mechanisms from dust it is necessary to make a frame that will protect it from environmental influences.

To make it, you can use a metal box or make protective screen from glass. It is also worth installing a casing that covers the end of the disk by a third. It will protect the worker if the abrasive disc cracks.

Photo of sharpening drills with your own hands

Note!

Note!

Drill sharpening can be done manually, on machines or with special abrasive discs.

If you sharpen the drill by hand, then you need to:

• hold the shank firmly and guide its spiral part with the other hand;
• press the cutting edge of the drill against the side surface of the abrasive wheel;
• after sharpening one side, it is necessary to smoothly rotate the drill, while the cutting edges must have the correct inclination to the axis and take the desired configuration.

The drill is sharpened on both sides alternately. At the same time, be sure to control the cutting edges.

Remember! The tip of the drill should be exactly in the center.

Otherwise, it will deviate during operation. It is worth noting that under no circumstances should you put too much pressure on the drill, otherwise it may get defects (bending).

For example, if after sharpening you notice that the cutting edges are not equal and are inclined at different angles to the axis, this means that the middle of the transverse edge is not in the center of the drill, and it will not work correctly.

When sharpening, be sure to pay attention to the initial angle of the tool. It is he who will become your guide in the future. Then inspect the gimlet for damage:

• if you find serious defects, you can use coarse sandpaper;
• if the defects are small and the drill is only slightly dull, use a finishing wheel. This operation is necessary for thin drills;
• if the concrete drill has defects in the shank taper, treat top part tool, gently pressing it against the grinding wheel;
• After processing, carefully inspect the back surface of the drill again;
• If you notice, or determine with a template, that you have a perfect cone, you have sharpened the tool correctly.

After this, process the cutting edge of the drill. The size of the jumper for rational turning of the tool should be 1-1.7 mm.

What are the features of sharpening machines?

A homemade device for sharpening drills is designed for through and blind drills made of steel, cast iron and various hard alloys. Depending on the type, machines can be equipped with different functions. On some of them, you can vary the angle during operation.

There are sharpening machines:

• universal – used for various cutting tools;
• specialized - for one type.

Devices for sharpening drills are classified as universal machines, because they can be used to process:

• taps;
• cutters;
• dugouts;
• countersinks.

Machines are divided into two categories:

1. Industrial - have high power and are designed for sharpening large-diameter tools. Power depends directly on the engine.
2. A household drill sharpening machine is quite compact and is often used for home use. It can be used to process even small-diameter drills.

There are seven sharpening methods:

1. Single-plane.
2. Complex screw.
3. Shaped.
4. Elliptical.
5. Conical.
6. Two-plane.
7. Screw.

How to make a device for sharpening drills

To make a homemade machine you will need:

• toggle switch;
• abrasive wheel;
• stub;
• engine;
• stand;
• wires.

Follow our tips:

1. For safety reasons, place homemade machine into the body, leaving only the axle and abrasive wheel outside. Remember, the device will work from the network.
2. Select in advance the location where your drill sharpening device will be placed. It is advisable that it be on a metal table.
3. Next, place the electric motor on the tabletop using fasteners (clamps) and mark the locations of the holes for the bolts, if it has legs.
4. After this, remove the electric motor and make 4 holes.
5. Later, reinstall the engine and secure it carefully with the bolts.

Advice: If the engine does not have legs, you can strengthen it with metal strips (clamps).

The electric motor for our future machine must be equipped with a special elongated shaft, onto which a granular disk should be placed. For this:

1. Install the fastening nut by first cutting a right-hand thread at the end of the shaft.
2. Secure the disc with a washer and nuts.

If the diameter of the shaft and the disc holes match, then install a washer on the shaft, and then an abrasive disc. If the diameter of the shaft and the hole do not match, then you will need to add a bushing.

First make a special side hole in it with a thread for a bolt in order to be able to secure it tightly to the shaft. After this you can put the sleeve on.

If you can't decide on an electric motor, then just take an old motor washing machine. It is ideal for homemade device sharpening.

It is worth noting that you must prepare in advance the starter and wires that will subsequently need to be connected. It is very important that the starter has at least three to four open contacts. Its winding must be connected using two buttons to the phase line.

Attention! The electric motor will be unsafe, regardless of the type - during operation, the rotating shaft can accidentally wind up a cord, wire, or hair.

Advice: Make metal box to protect the machine from dust, abrasive particles, and you from accidental injuries.

How to properly sharpen a drill on a machine

1. When sharpening, you must ensure that the two shoulders of the drill are identical. If you achieve such a correspondence, then the axis of rotation of the drill will completely coincide with the center of the hole.
2. Before you start sharpening, be sure to ensure that the abrasive disc is tightly secured.
3. Always start the process with a coarser abrasive. Once a burr appears on your drill, you can change the abrasive to a finer one.
4. Watch the sharpening angle.
5. Do not allow the windings to switch so that the abrasive disc rotates in reverse. It should always move only in the direction of the blade.

Please note that drills cannot tolerate excessive overheating. Cool the gimlet regularly while sharpening. But under no circumstances put a red-hot drill into water, as cavities may appear in it.

Additional accessories

1. Guide

To avoid holding the drill suspended during sharpening (this can lead to injury), provide a support or guide in the form of a small attachment. It is made from a strip of metal, bent as shown in the figure and screwed to the frame (base). The drill is rested on it and brought to the circle at the desired angle.

1. Goniometer

Make marks (marks) on the guide described above for the required sharpening angles. It will become much more convenient to use.

If this is difficult for you, cut off the top part of a regular protractor and glue it to the guide.

Angles less than 30 0 are not used for sharpening, so we sacrifice them.

1. Universal device

To facilitate sharpening of tools, in particular drills, a mechanism has been developed consisting of a drill chuck, a shaft, roller guides (sled) and a protractor.

The main substrate described above is made wide. A protractor is glued onto it. A hole is drilled into which a bolt is inserted, which serves as an axis for the rotating surface.

A plate is installed on it on a roller slide, on which a pipe with a cartridge on the axis is fixed. The plate itself moves forward/backward using a conventional feed mechanism (threaded axis).

At the bottom of the rotating plate there is a displacement limiter indicator. It serves to rotate the device to the desired angle and to lock it.

Working with the device