Machining operations on workpieces on lathes rarely become final in the process. Creating holes is the main step in obtaining the necessary shape of the part. But as a rule, it is followed by a stage of refinement. In part, these are finishing correction measures, but sometimes methods of basic changes in the parameters of the performed cut are also applied. Such operations include countersinking and hole drilling, as a result of which the operator receives a workpiece that is optimal in characteristics. Firstly, the prepared recess acquires the necessary dimensions, and secondly, its edges and surfaces are cleaned of excess burrs and shavings.
What tasks does the core drilling solve?
Openings of different origin are allowed to the countersinking procedure. These can be cast, stamped or drilled niches over which the countersink master will continue to work. What is the essence of this operation? She can have two goals. At a minimum, surface cleaning of the hole will be ensured. This is especially important in cases where rough drilling and expansion of holes whose edges need to be refined is preliminarily performed. Depending on the quality of the hole formation, a semi-finishing or finishing countersinking can be used. As a result, the degree of smoothing of the working surfaces also changes. The calibration task is even more responsible. In this case, the master is not limited to stripping and adjusts hole parameters, such as depth and thickness. The need for such actions arises if the originally obtained hole is not suitable for the size of the target stud, screw or other fastener. After countersinking, the thread is cut in accordance with the size of the hardware.
What is a countersink?
This is a cutting tool, the design of which is formed by a functional machining part and a tool holder. Outwardly, some types of countersinks resemble drills, but they are much stronger. And an even more important difference is the presence of at least three cutting edges, providing a more efficient removal of excess metal mass. By the way, this also distinguishes the deployment of holes, which sometimes requires intensive elimination of chips in order to achieve a more accurate shape of the workpiece. But at the countersink, several cutting edges also act in some way as a tool stabilizer. This aspect ensures the uniformity of the processing of the edges, which affects the accuracy of the operation. However, the quality of the result will depend on how correctly the type of instrument was chosen.
Varieties of countersinks
The simplest conical countersink models consist of a cutter and a shank. The cone angle in the working part can vary from 30 to 120 °. A more sophisticated variation of the tool is a face teeth cutter. The number of teeth on average is from 4 to 8. Accordingly, the more accurate the reaming is required, the smaller the surface of the cutter should be. There are also cylindrical devices in which a guide pin is provided. It enters the formed holes, thus ensuring the coincidence of the formed cylindrical recess and the axis of the hole. This is a universal technique in which drilling, coredrilling and reaming of holes are performed using a single formation tool. As a result, the cycle of hole formation is simplified and the quality of cleaning adjacent surfaces is improved. Almost all countersink models are made of tool alloyed and carbon steels.
Counterbore Technique
Typically, countersinking is performed on drilling machines. Like drills, countersinks are mounted in appropriate chucks or clamping mechanisms. Further, the output parts of the holes are processed with conical countersinks. This technique forms conical recesses suitable for rivet heads and countersunk screws. Recesses for bolts are made in the same way, but with cylindrical countersinks. This tool also performs trimming of the ends, the selection of angles and protrusions. Both core drilling and hole drilling on the machine are controlled by the operator. In modern models of pneumatic and electric machines, the possibility of processing in semi-automatic and automatic modes is allowed. Software-controlled machines can use similar counterbore settings for serial part maintenance.
Deployment Operation Purpose
The deployment operation is in many ways similar to countersinking. It is also designed for the formation of optimal size holes with the possibility of shape correction. But if the countersinks prepare holes for the subsequent use of rivets and bolts, then the deployment allows you to get accurate calibrated niches for shafts, plunger parts and bearings. Also, the deployment of holes allows to minimize friction in the treated area and to provide a high density of contact between the elements. These tasks are achieved by reducing the surface roughness of the hole.
Deployment tool
Reamers are also a tool resembling drills. The working part in this case is provided by the teeth located around the circumference of the shaft. In addition, there are auxiliary functional parts of the cutter. These are intake, gauge and cylindrical parts. Direct cutting is performed by a guide cone, the edges of which remove the metal allowance, but at the same time protect the top of the cutting edge from nicks. And here you can highlight the individual structural parts that distinguish this technique and countersinking. Sawing and reaming of holes converge in cutting operations, however, the calibrating part of the reamer also performs the functions of guiding and removing chips. To do this, special grooves are made to make the tool more independent.
Machine and manual reamers
Deployment can be performed manually and machine-wise, that is, on the same machines. The tool used for manual operations is characterized by an elongated working part. The diameter of the inverse cone in this case varies from 0.06 to 0.1 mm on average. For comparison, machine reamers have a cone thickness of 0.05 to 0.3 mm. Using manual deployment, you can get holes with a diameter of 3 to 60 mm. In this case, the degree of accuracy will be small. Machine tools are guided by certain sizes, often by special orders. For example, the deployment of holes in parts for building structures can be performed in accordance with the technical data for a specific project. The advantages of this method include high precision cutting, high-quality cleaning and the absence of a deformation effect.
Deployment Execution
Machine deployment follows the same principles as countersinking. The tool is fixed in the chuck, and then sent to the machined area by the machine. The only difference is the higher requirements for cooling the working equipment during operation and lubrication of the holes. Mineral oil, turpentine and synthetic emulsions are used as a lubricating composition. Otherwise, manual hole machining is performed. The deployment of this type involves the initial fixation of the workpiece in a vise. Next, the sweep tip is inserted into the hole and the result is achieved by twisting the knob. Moreover, the tool can only be rotated in one direction - until the necessary product parameters are formed.
Conclusion
Machining of metals is gradually giving way to technological laser and thermal methods. Also competing with traditional cutting methods is waterjet technology, which is characterized by high cutting speed and accuracy. What can a countersink, as well as the deployment of holes, offer against this background? First of all, it is the possibility of manual processing without the use of complex equipment in the form of machines. In addition, unlike waterjets and thermal apparatuses, these technologies do not require the connection of additional consumables. Therefore, we can talk about the benefits of an economic, organizational and ergonomic nature. But the quality of processing and the pace of the production process, of course, have to sacrifice.