Countersinking and unfolding of holes

The operations of machining billets on turning machines rarely become final in the technological process. The creation of holes is the main step in obtaining the required shape of the part. But behind it, as a rule, follows the stage of refinement. In part, these are measures of finishing correction, but sometimes methods of basic change of the parameters of the cut are applied. Such operations include countersinking and opening of holes, as a result of which the operator receives the optimal workpiece. First, the prepared groove acquires the necessary dimensions, and secondly, its edges and surfaces are cleaned of excess burrs and shavings.

What tasks does baling solve?

To the sinking procedure, openings of different origin are allowed. It can be cast, stamped or drilled niches, over which the master of the countersink will later work. What is the essence of this operation? It can have two goals. At a minimum, the surface of the hole will be cleaned. This is especially important in cases where rough drilling and deployment of holes are preliminary performed, the edges of which need to be refined. Depending on the quality of the formation of the hole, semi-finished or final reaming can be used. As a result, the degree of smoothing of the working surfaces also changes. The task of calibration is even more important. In this case, the master is not limited to sweeping and adjusts the hole parameters, for example, depth and thickness. The need for such actions arises if the initially obtained hole does not fit in size to the target hairpin, screw or other fastener. After the countersinking, the threads are threaded in accordance with the dimensions of the hardware.

What is a countersink?

This is a cutting tool, the construction of which is formed by a functional machining part and a shank-holder. Outwardly some types of countersink resemble drills, but they are much stronger. And even more important difference lies in the presence of at least three cutting edges, which ensure more efficient removal of excess weight of metal. By the way, this also differs and the deployment of holes, which sometimes requires intensive chip elimination in order to achieve a more accurate shape of the workpiece. But in the sinker, several cutting edges also act in some way a tool stabilizer. This aspect guarantees the uniformity of edge processing, which affects the accuracy of the operation. However, the quality of the result will depend on how well the type of instrument was chosen.

Varieties of countersinkers

The simplest conical models of the reeds consist of a carver and a shank. The angle of the cone in the working part can vary from 30 to 120 °. A more complex variation of the tool is a carver with end teeth. The number of teeth on average is from 4 to 8. Accordingly, the more precise the reaming is required, the less the surface of the carver must be. Also there are cylindrical devices in which a guide pin is provided. It enters the formed holes, thus ensuring the coincidence of the formed cylindrical depression and the axis of the hole. This is a universal technique, in which drilling, reaming and deployment of holes are produced by the tool of a single formation. As a result, the hole forming cycle is simplified and the quality of cleaning of the adjacent surfaces is improved. Almost all models of countersink are made of instrumental alloy and carbon steels.

Sinking technique

Usually the countersinking is performed on drilling machines. As well as drills, the countersinks are installed in appropriate cartridges or clamping mechanisms. Then the outlet parts of the holes are treated with conical countersinks. According to this technique, conical grooves are formed, suitable for rivet heads and secret screws. The grooves for bolts are produced in the same way, but already with cylindrical countersinks. This tool also performs trimming of ends, a selection of corners and protrusions. Both the countersinking and the opening of the holes on the machine are controlled by the operator. In modern models of pneumatic and electrical machines, the possibility of processing in semi-automatic and automatic modes is allowed. Machine tools with programmable control can use similar settings for processing by countersink for serial maintenance of parts.

Purpose of the deployment operation

The deployment operation is largely similar to the countersink. It is also designed to form optimal in size holes with the possibility of shape correction. But if the counters prepare holes for the subsequent use of rivets and bolts, the deployment allows you to obtain accurate calibrated niches for shafts, plunger parts and bearings. Also, the deployment of the holes makes it possible 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 roughness of the hole surfaces.

Deployment tool

The sweeps are also a tool reminiscent of a drill. The working part in this case is provided by teeth located along the circumference of the rod. In addition, there are auxiliary functional parts of the carver. These are sampling, calibrating and cylindrical parts. Direct cutting produces a guide cone, the edges of which remove the allowance of metal, but at the same time protect the top of the cutting edge from the nicks. And here it is possible to distinguish separate constructive parts that distinguish this method and countersinking. The countersinking and unfolding of the holes converge in cutting operations, but the calibrating part of the sweep also functions as a direction and a chip removal. For this purpose special grooves are provided, making the tool more independent.

Machine and manual sweeps

Deployment can be carried out manually and mechanically, that is, on the same machines. The tool used for manual operations is characterized by an elongated working part. The diameter of the cone in this case varies from 0.06 to 0.1 mm on average. For comparison, machine sweeps have a cone thickness of 0.05 to 0.3 mm. With the help of manual deployment it is possible to obtain holes with a diameter of 3 to 60 mm. At the same time, the degree of accuracy will be small. The machine tool is oriented to certain sizes, often on special orders. For example, the deployment of holes in structural components can be carried out in accordance with the technical data for a particular project. The advantages of this method include high accuracy of cutting, high-quality stripping and no deformation effect.

Deploying

Machine deployment is performed according to the same principles as countersinking. The tool is fixed in the chuck and then sent to the machined zone by the machine tool. The only difference is the higher requirements for cooling the working tools during operation and lubricating the holes. As a lubricant used mineral oil, turpentine and synthetic emulsions. Otherwise, the holes are manually machined. Deployment of this type assumes the initial fixation of the workpiece in the vice. Further into the hole is inserted the tip of the sweep and by twisting the wrench the result is achieved. And you can rotate the tool only in one direction - before forming the necessary parameters of the product.

Conclusion

Mechanical processing of metals gradually gives way to technological laser and thermal methods. Also, the competition with traditional cutting methods is hydroabrasive technology, characterized by high cutting speed and precision. What on this background can offer countersink advantages as well as opening of holes? First of all, this is the possibility of manual processing without the use of complex equipment in the form of machines. In addition, unlike hydroabrasives and thermal devices, these technologies do not require the connection of additional consumables. Therefore, we can talk about the benefits of economic, organizational and ergonomic nature. But the quality of processing and the pace of the production process, of course, have to be sacrificed.