A drill is perhaps one of the most common devices for mechanical processing of materials both in everyday life and in production, which allows you to quickly and accurately make a hole in a surface with a very different structure. Whether it's a hand drill, an electric drill, or a large radial drill, they all use a drill as a cutting tool. It is a hardened carbide metal rod of various diameters, with a shank and a working part in the form of two or more cutting edges, which, during rotation, select material.
Drill angle: individual approach to each material
Depending on the type of surface, the requirements for the quality of processing and a number of other conditions, the shape of the drill can have a very different look. The most common option is when its working part consists of two spirally twisted cuttingedges forming a cone at the end of the drill, the height of which determines the angle of sharpening the drill. Its value depends on the hardness of the material being processed and for each material it can have its own values:
- carbon steels, cast iron alloys and hard bronze - 116º to 118º;
- brass, soft bronze and copper products - from 120º to 130º;
- aluminum and wood surfaces - 140º;
- polymers and plastics - from 90º to 100º.
Conditions for a long and active life of the drill
If we exclude the thoughtless (or hopeless) option of using a drill without victorious soldering to work on concrete or stone (when the tool fails in just a minute), then the most active cutting edges become dull when drilling hard metals. The service life of the drill in this case depends on the hardness of the surface to be machined, as well as the speed of rotation, the feed force and the presence of cooling of the cutting tool. It is extremely simple to determine the moment of deterioration in the cutting qualities of the drill by the characteristic sharp whistle and the need for more pressure on the drill. As a result, the drill heats up very quickly, the drilling time is significantly increased with a simultaneous decrease in the quality of the resulting hole, and the drill must be replaced to continue normal operation.
Better to lose an hour and then drill in five minutes
Because drills are considered consumables and have a relatively low cost in small sizes, many of them are simply thrown away and replaced with new ones. However, such an approach canbe justified only with a small amount of work, a low price of the part and the proximity of a hardware store. It is much more economical and faster to sharpen a drill for metal with your own hands. There are a lot of devices for this operation, and, as a rule, the price of such equipment directly depends on the speed, versatility and quality of processing the cutting tool.
The correct form of sharpening is the key to efficient work
As a result of processing, the cutting edge of the drill is given a certain geometry, which is a priority for a particular diameter of the drill and the structure of the surface to be machined. To obtain the required shape, respectively, different methods of sharpening the cutting edge are used. Separate single-plane, conical, two-plane, screw and cylindrical types of sharpening. At home, the first two methods are most often used as the simplest, and drills with a diameter of up to three millimeters are sharpened in one plane, providing a thirty-degree slope of the rear corner. The disadvantage in this case is the high probability of destruction of the working part of the edge due to its thinning, therefore, for larger diameter drills, sharpening in the form of a cone is usually used, forming an angle of 118-120º on their tip.
Ways to achieve the desired sharpening quality
In principle, having certain skills, sharpening can be done without an auxiliary tool. The main thing in this case is to observe the required processing angle, as well as the equal length of the working surface of the cutting edges and their symmetrical inclination.relative to the axis of the drill. However, it is not so easy to achieve this in practice, a very small error in any of the listed indicators is enough, and your drill will not work properly. The use of special tools simplifies the process, but you must admit that it is not advisable to purchase an expensive machine to tidy up a pair of metal drills. In addition, a home-made device for sharpening drills will help to cope with this task, albeit with less comfort, but also not bad.
With all the variety of performance options, the principle of operation of all devices of this type is based on the formation of a rigid template or guide along which the tool to be sharpened is fed to the emery wheel in a certain plane.
Nut, screw, direction - that's all the fixture
Perhaps one of the fastest and most affordable options would be to make a tool for sharpening drills from a nut. Its six faces form an angle of 120º on adjacent planes and can serve as an excellent template for setting the desired inclination of sharpening the cutting edge of the drill. The procedure for manufacturing such a device is quite simple and does not take much time. The nut is clamped with the flat side up in a vise and, using an angle grinder (grinder), longitudinal cuts are made along the line connecting the opposing corners of the hexagon. On one side of the hardware, you can make six recesses (according to the number of vertices), thus forming three guides.
Nut size, as well as the width and depth of the samplethe guide is selected based on the diameter of the drill being sharpened. After that, the entire outer surface of this simple device is carefully treated with sandpaper or a file to remove burrs.
That, in fact, is all, the simplest device for sharpening drills with your own hands is ready. Now the drill requiring sharpening is placed inside the guide (between two opposing corners) so that the edge to be machined slightly protrudes beyond the top of the hexagon. The fixture is clamped in a vice, tightly fixing the drill in the groove of the nut with the tip up, and using the same grinder, carefully grind off the protruding cutting edge, using the side surfaces of the hardware as a guide, forming a sharpening angle of 120º.
If necessary, the drill in the groove can be fixed with a clamp, and instead of an angle grinder, a grinder with an emery wheel is used.
Hardware can never be too much: modernization of the wrench
This design can be slightly improved by making deeper (depending on the diameter of the drill being sharpened) V-shaped cuts in opposing peaks and welding a smaller nut on the same side of the device. The drill in this case can be fixed with a clamping screw screwed into a nut welded on top.
As a result, there is no need to use a vice and a clamp (the main thing is not to pinch the screw so as not to bend the drill). Similarthe device allows you to successfully cope with the sharpening of even small diameter drills (up to three millimeters), when it is almost impossible to withstand and control the sharpening angle without special tools.
Wooden guides for sharpening drills
Now let's look at how to make a drill sharpener from bars or thick plywood. The design is a wooden guide rigidly attached to the base. The base part of the device is made of a flat rectangular board (thick plywood) on one side of which a rectangular cutout is made to provide access to the side surface of the emery wheel. Then, an overlay is prepared from plywood in the form of a right-angled triangle or a trapezoid with a side slope at the base of 60º (from the top - 30º), which guarantees a sharpening angle of 120º. The dimensions of the guide should ensure free placement of the drill being sharpened along it both in length and in height.
The finished overlay is attached to the far edge of the base board with an acute angle towards the emery wheel using self-tapping screws. Sharpening drills for metal with a device of this type requires its precise fixation along the outer (wide) surface of the abrasive. Each cutting edge is formed separately by smoothly rolling the drill against the rotation of the circle, then the same procedure is repeated for the second side, achieving perfect balance. With frequent use on the circle, wear may occur, and you will either have to move the device alongemery, or replace the abrasive. This method is good in that it makes it easy to obtain the required inclination of the cutting edge by quickly changing the top guide to the required size.
Use guide bushings for sharpening
Another option for processing drills, actively practiced at home, is a wooden vertical stand with hollow metal bushings of various diameters, which are placed in the bar at the angle required for sharpening. Machining results in a taper on the back of the cutting edges, but without the correct relief angle.
Professional solutions: great results for little money
All homemade devices provide an acceptable, but, alas, imperfect result. Even without taking into account the high probability of error in the self-manufacture of sharpening devices, there are still a number of parameters, non-compliance with which leads to a quick failure of the drills. That is why major manufacturers are developing complex devices and even machines to bring cutting tools into working condition.
One of these mechanisms is the drill grinde, which makes it possible to restore sharpness to spiral drills for metal with a diameter of three to nineteen millimeters. The device easily copes with the task of forming a cutting edge of any inclination, while having a scale with standard sharpening angles (98, 118, 136 and 176 degrees, as well as for countersinks). Perfect sharpening qualityguaranteed by precise positioning of the drill thanks to the clamping screws. The heel (rear angle of the cutting surface) is formed due to a small axial inclination, which sets the arc movement of the drill during processing.