Drilling is an important stage of many works, including at home. Over time, the drills wear out and it becomes harder to drill. Sharpening your own hands allows you to get rid of this problem.
Diagram of the device drill metal.
Of course, to drill a drill, especially if it is made of special materials, it is better for professionals on industrial machines, but this is expensive and not always possible for many reasons. Sharpening at home means having a sharpening tool, but you need to buy it once and for a long time. And in everyday life it is useful for other purposes.
Features of the drilling process
Types of sharpening drills.
The principle of any drilling is based on the formation of a conical recess in the material and its gradual deepening, due to the rotational movement of the cutting edges of the drill. Accordingly, the cutting edge wears with uneven contact with hard surface. The symmetry (roundness) of the cutting part is broken, and the center of rotation is constantly shifted during the drilling process.
During drilling, solid metal chips of various sizes accumulate inside the hole being machined. Such particles play the role of abrasive material and erase the working surface of the drill. In addition, friction when drilling causes the tool to warm up, which significantly increases the rate of wear of the material.Back to table of contents
Drill sharpening patterns.
The main indicator of wear is the drilling time. A significant increase in the time of such an operation indicates the need for sharpening. When processing wood or plastic, this phenomenon is rarely observed, but when working with steel or copper parts, wear of the cutting tool occurs quite quickly. In this case, there are difficulties in the formation of an initial cone on the metal surface.
A clear manifestation of the loss of functional abilities is the emergence of a sound similar to a sharp creak, even when drilling a surface. When working with a poorly sharpened drill during operation, a greater amount of heat is generated, which strongly heats the tool and accelerates its wear.
Finally, the sharpness can be checked by touch with a finger along the cutting edge, or visually according to the state of the conical part. In order to continue working with the worn drill, it needs to be sharpened.Back to table of contents
Conical method of sharpening the drill.
In the domestic environment is usually used drill-type spiral of different diameters. Tools are made of alloyed steel or won, and may also contain reinforcing soldering.
Drills have a standard design and consist of a working part, a neck and a shank. The working part, which is a spiral section, has a tapered cutting part at the end. On the shank is made foot for fastening the drill in the tool.
The spiral working area consists of two front (recessed) and rear surfaces. On one of the boundaries between the surfaces there is a ribbon, forming a cutting edge. The end cutting part of the work area is a cone, at the top of which the front and rear surfaces converge, forming two teeth (feathers). In the tapered part of the ribbon forms the cutting edge of the cone. At the apex of the cone, where two ribbons converge, a transverse edge and a web are formed. The front surface forms a groove.
The most important parameter of the cutting tool is the angle of sharpening of the cone, which is the angle between two ribbons at the apex of the cone. Naturally, the smaller the angle, the longer the tapered cutting part and the sharper the drill. For drilling different materials are selected drills with different angle sharpening. For most types of steel, this angle is chosen to be 90 °, for copper and aluminum - 90-100º, for bronze and brass - 110-120º, for wood - 90-100º.Back to table of contents
The principle of sharpening the drill
Scheme sharpening drill.
The purpose of sharpening is to sharpen the cutting edge, create the necessary taper angle and ensure the centering of the drill. The goal is achieved by processing using an emery element. Sharpening can be done manually, using devices or on special equipment. The main task is a thin and precise tool processing with reliable fixation of its position.
The condition is assessed visually and by measuring with a caliper. The angle of the cone is best checked using a template. The angle must correspond to the recommended values. The size of the jumper at the apex of the cone should not exceed 0.4 mm for drills with a diameter of up to 10 mm and 1.5 mm for drills of a larger diameter. This parameter determines the sharpness of the cutting cone.
If a visual inspection reveals a strong wear on the cutting part, then the drills should be sharpened with coarse emery. For less serious defects, a fine-grained disc can be used. For insignificant wear of the surface, a circle with a velvet abrasive is sufficient.
The alignment is checked by measuring or visual evaluation of the length of the ribbons (hangers) from the top of the cone to its base.
The length of both ribbons should be the same. The cutting element of the drill should have the appearance of a correct cone.Back to table of contents
The process of sharpening the drill
Elements of spiral drill.
It is best to sharpen the drill using a grinding machine. Before sharpening, it is recommended to mark with a red dot the top of the cone (center). The drill is brought to the grinding wheel of the machine in a horizontal direction relative to the table. In this case, the machined surface of the cutting element must be strictly parallel to the surface of the circle, that is, the drill, when machining the tapered part, is guided to the surface of the circle at an angle equal to half the angle of the grinding of the cone.
Sharpening the cutting edge is carried out by processing the back surface. Both teeth on the cutting cone must be machined exactly the same. Feed the drill to the circle with both hands. The left hand locks the tool in a given direction, and the right hand rotates the drill clockwise. Both hands slowly move forward to handle the entire length of the cone. During sharpening, do not tear the part from the surface of the circle. Hand movement should be slow and smooth.
Elements of the working part of the drill.
The grinding process should be monitored by the red dot in the center of the drill. Similarly, the second tooth of the cone is ground. The sharpening angle is controlled by the template. With a lack of sharpening process is repeated.
If it is necessary to sharpen the cutting edge on the cylindrical part of the drill, the processing of the ribbon of the back surface is carried out at the end of the grinding wheel. In this case, the tool is held parallel to the surface of the circle.
Processing begins with the installation of coarse abrasive. Then the processing is carried out using a circle of fine grain. Finishing is carried out polishing surface. In the latter case, we can recommend a green circle based on silicon carbide with a grain size of 5-6. When sharpening, it should not be overheated. The risk of overheating is reduced by regularly cooling the drill with water.Back to table of contents
Use of devices
Diagram of the device for sharpening the drill.
When sharpening drills manually, the main difficulty lies in the reliable fixation (retention) of it relative to the grinding wheel. To eliminate this, various simple, hand-made accessories are used. For example, a device made on a tripod base is recommended. The drill is fixed on the plate with a retainer.
The movement of the drill in the longitudinal direction is carried out using an adjusting screw. On the rack there is a scale with markings of installed angles, with the possibility of fixing the four most common angles.
The correct processing of the cutting surface is ensured by the reliable holding of the drill in the clamp and the accuracy of the stroke provided by the adjusting screw. The processing of the entire back surface of the drill is carried out due to the slight inclination of the drill axis and the possibility of its movement along the arc.Back to table of contents
Features sharpening pobedit drills
Scheme angle sharpening drill.
When machining pobedit drills, it is necessary to use a diamond stone grinding wheel. The speed of sharpening such a tool should be less than steel. The sharpening of the drill itself is done with quick, short touches of the cutting surface to the diamond wheel. Grinding is victorious very quickly, so the contact of the drill with the stone of the circle should be of minimum duration.
Hardening taps are also sharpened at home. In general, the process is similar to sharpening steel options. Particularly necessary to monitor the heating material. Overheating may cause cracking of the braze. In addition, it is desirable to process the front surface to center the soldering.Back to table of contents
For sharpening drills at home, the following tools and equipment are needed:
- grinding (grinding) machine;
- emery block;
- emery sandpaper;
Provide each house with special machines for sharpening drills unrealistic. But it is quite possible to make a manual sharpening when receiving small skills of using grinding wheels.