Rectangular hole in metal. Drilling square holes. Drill structure for square holes

In some cases it is necessary to obtain square-shaped holes. Conventional methods are inefficient and cumbersome. The most primitive of them comes down to preliminary drilling a hole with a diameter equal to the circle inscribed in a square, and gradually punching it out. You will need a tool that can work without rotating the tool head, as well as a special adapter. It’s easier to use a so-called “square” drill (Watts drill), or, more precisely, a cutter.

A little history with geometry

Back in the 15th century, the legendary Leonardo da Vinci, while studying the properties of geometric figures, drew attention to the so-called geometric objects with equal thickness. There are an infinite number of such figures, but the simplest - besides a circle - is a rounded triangle, which can be formed as follows. An equilateral triangle is drawn, each of the corners of which is connected by an arc of a circle drawn from the center of the opposite side. The peculiarity of such a triangle will be that all its sides will have a constant width, which is equal to the length of the side of the original equilateral triangle.

L. Euler drew practical benefit from this fact, who three centuries later demonstrated the rotation of such a rounded triangle: first around its own axis, and then with some eccentricity, since the cardan mechanism was already known to science and technology of that time.

The German engineer F. Relo went even further in the practical use of this figure, who drew attention to the fact that the trajectory of the corners of a moving triangle with certain methods of its rotation is very close to a square. Only directly at the corners of the square does the outer surface describe an arc, however, of a small radius. In modern technical literature, such a triangle is called the Reuleaux triangle, although this figure actually no longer has any angles.

A few more decades will pass, and the Englishman G. Watts will come up with a device that can provide a guaranteed square trajectory for a metal-cutting tool. The technical solution for the Watts drill was patented in 1916, and a year later mass production of such tools began.

Drill or cutter?

The majority of the technical community believes that it is still a milling cutter. However, manufacturers stubbornly continue to call this tool a drill for square holes, a Watts drill, or a drill whose profile corresponds to the Reuleaux triangle.

Which is more correct? If we turn to the kinematics of movement of such a cutting tool (for clarity, you can use the diagram shown in Fig. 1), you will find that metal removal will be carried out only by the side surface, and there will be not one cutting plane, like a conventional drill, but four, which more typical for cutters.

However, a single rotating motion will not be enough to obtain a square hole. Simple mathematical calculations (not given in this article) show: in order for a “drill” for a square hole to perform its function, during operation it must describe not only the basic rotational movement of the cutting edge, but also the rocking movement of the drill/cutter around a certain axis. Both movements must be made in mutually opposite directions.

Figure 1 – Reuleaux Triangle: a) – construction; b) rotation sequence to obtain a square-shaped hole.

The angular velocity of both rotations is determined quite simply. If we take the rotation frequency of the drill shaft (or hammer drill) as the parameter f, then a speed of 0.625f is sufficient for oscillatory rotations of the spindle around its own axis. In this case, the spindle axis is, as it were, clamped between the working shaft and the drive wheel, causing the drill/cutter to oscillate in the clamping device with a residual speed

(1 – 0.625)f = 0.375f.

The resulting rotation speed of the cutter can be more accurately determined using the technical characteristics of the drill/hammer, but it is clear that it will be much lower than that for which the tool was originally designed. Therefore, obtaining a square hole will occur with less productivity.

Design and principle of operation

It is impossible to directly use a cutter/drill for square holes with a Reuleaux triangle profile - grooves are needed to remove the resulting chips.

Therefore (see Fig. 2) the profile of the working part of the tool is the figure described above, from which three half-ellipses are cut out. In this case, three goals are realized: the moment of inertia of the drill and the load on the spindle are reduced, and the cutting ability of the cutter is increased.

Figure 2 – Actual profile of the working part of the tool

The design of the tool is as follows. Actually, the working part includes a working surface used to remove metal and grooves that remove chips. A cutter-drill for square holes is made from U8 steel and hardened to a hardness of HRC 52...56. Under particularly severe operating conditions, products made of X12 alloy steel with a hardness of HRC 56...60 are used. With normal coolant supply and due to relatively low temperatures in the processing zone, tool life is high.

The adapter spindle has a more complex design. It includes:

1. Frame.
2. Ring gear.
3. A seat for the main spindle (if the tool is installed in the tool head of a metal-cutting machine, then the adapter has the form of a Morse cone).
4. Drive gear.
5. Main spindle.
6. Meshing gears with a ring gear.
7. Oscillating bushing.

For household devices, manufacturers of cutters/drills for square holes offer overhead frames that are connected by a cardan drive to the chuck and impart eccentric movements to the cutting tool. The thickness of this frame determines the depth of the resulting hole.

To connect the device to the machine chuck, a special adapter is also required. It consists of:

1. Cases.
2. Floating shank.
3. Swinging ring.
4. Replaceable bushings for cartridges of various metalworking machines.
5. Mounting screws.
6. Support balls.

For the practical use of the tool in question, it is enough to give the spindle of the main equipment a feed in the required direction. Broaching milling machines and lathes are suitable for making square holes using such equipment.

Alternative Methods for Making Square Holes

The disadvantage of Watts drills is the presence of radius arcs in the corners of the square, which is not always acceptable. In addition, square hole drills made using the Reuleaux triangle cannot handle thick workpieces. In such cases, you can use electroerosive/laser technologies, and also, which is easier, use welding or stamping.

Sets of punches for square holes are produced in an assortment of transverse sizes up to 70×70 mm in metal with a thickness of up to 12...16 mm. The kit includes:

• Punch holder for punch.
• Guide bushing.
• Ring travel stop.
• Matrix.

A hydraulic jack can be used to exert force on the punch. The punched hole is distinguished by the cleanliness of the resulting edges, as well as the absence of burrs. A similar tool is produced, in particular, by the Veritas trademark (Canada).

If you have a welding inverter in your household, you can burn a square hole in a steel part. For this purpose, a round hole is pre-drilled (with a reserve) in the workpiece, then a square of graphite grades EEG or MPG of the required size is inserted into it, after which it is scalded along the contour. The graphite is removed, and a square hole remains in the product. If necessary, it can be cleaned and sanded.

Almost everyone knows how to drill a round hole, but not everyone knows about a drill for square holes. Meanwhile, you can drill a square-shaped hole both in soft wood products and in harder metal parts. To solve this problem, special tools and devices are used, the operating principle of which is based on the properties of the simplest geometric shapes.

Operating principles and design

In order to drill a square hole, a Watts drill is usually used, the design of which is based on a geometric figure such as the Reuleaux triangle. One of the most important features of such a figure, which represents the area of ​​intersection of three equal circles, is the following: if a pair of parallel reference lines are drawn to such a triangle, then the distance between them will always be constant. Thus, if you move the center of the Reuleaux triangle along a trajectory described by four ellipsoidal arcs, its vertices will draw an almost perfect square, with only slightly rounded vertices.

The unique properties of the Reuleaux triangle made it possible to create drills for square holes. The peculiarity of using such a tool is that the axis of its rotation should not remain in place, but move along the trajectory described above. Naturally, this movement should not be hindered by the equipment cartridge. When using such a drill and the appropriate equipment, a square hole is obtained with perfectly straight and parallel sides, but with slightly rounded corners. The area of ​​such corners not processed with tools is only 2% of the area of ​​the entire square.

Making a device for drilling square holes

Using Watts drills, which work on the principle of the Reuleaux triangle, you can drill square holes in metal workpieces even on a regular machine that is not equipped with special attachments. To create a square hole in a wooden part, you can use a regular drill, but for this it must be equipped with additional devices.

You can make a simple device that allows you to drill square holes in wooden blanks using the following recommendations.

• To begin with, using a sheet of plywood or a wooden board of small thickness, you need to make the Reuleaux triangle itself, the geometric parameters of which must correspond to the diameter of the Watts drill used.
• The drill must be firmly fixed on the surface of the manufactured triangle.
• In order for the Reuleaux triangle and the drill attached to it to move along the required trajectory, it is necessary to make a wooden guide frame. In the inside of the frame, you should cut out a square with geometric parameters that fully correspond to the dimensions of the hole that you are going to drill.
• The frame is fixed to the drill using a special strip, and the center of the Reuleaux triangle placed in the guide frame must coincide with the axis of rotation of the power tool chuck.
• In order to impart torque to the drill for making a square hole, but at the same time not create restrictions on the movement of the tool in the transverse direction, the shank is connected to the drill chuck through a transmission mechanism that operates on the principle of a truck drive shaft.
• The wooden workpiece in which it is necessary to drill a square hole should be securely fixed, and it should be positioned so that the center of the future hole strictly coincides with the axis of rotation of the drill used for processing.

Having assembled such a simple device and securely fixed all the elements of its design and the workpiece being processed, you can turn on the electric drill and begin the drilling process.

As mentioned above, a square hole drilled using such a device will have absolutely straight and parallel sides, but its corner sections will be slightly rounded. Solving the problem with rounded corners is not difficult: you can refine them using a regular needle file.

It should be borne in mind that the device described above, which is not very rigid, is used for drilling square-shaped holes in wooden pieces of small thickness.

Watts drill and a square hole made with it in a metal workpiece

The simplest figure of the hundred-yang shi-ri-na will help us in drilling square holes. If you move the center of this “triangle” along a certain trajectory, then its vertices are drawn almost like a square, and the he will sweep the entire area inside the radiant figure.

The edges of the best figure, except for small pieces in the corners, will be strictly straight ! And if you continue to live from the cutting, then you will see the corners, then the result will be exactly a square.

In order to be described above, the center of the triangular Re-lo needs to be moved along the trajectory, clearly la-yu-shchey-glue-coy from four one-to-one arcs of el-lip-owls. The centers of the el-lips are located at the tops of the square, and along the axis, at an angle of $45^\circ$ from-but-si-tel-but the sides of the square are equal to $k\cdot(1+1/\sqrt3)/2$ and $k\cdot(1-1/\sqrt3)/ 2$, where $k$ is the length of a hundred square meters.

Curved, rounded corners also appear as du-ga-mi el-lip-sovs with centers in the corners of squares , their half-axis is at an angle of $45^\circ$ from the sides of the square and is equal to $k\cdot(\sqrt3+ 1)/2$ and $k\cdot(1/\sqrt3-1)/2$.

The area of ​​the invisible corners is only about 2% of the area of ​​the entire square!

Now, if you make a drill in the form of a triangular Re-lo, then you can drill square holes with a little -go-round-the-corner-of-me, but ab-so-lyut-but straight-we-a-hundred-on-mi!

All that's left is to make that drill... Or rather, it's not difficult to make the drill itself, you just need it to fit in this is the triangle of Re-lo, and the cutting edges of the owls are with its tops.

The difficulty lies in the fact that, as already mentioned above, the tra-ek-to-ria of the center of the drill must be -one hundred of four arcs of el-lip-owls. Vi-zu-al-but this curve is very similar to a circle and even ma-te-ma-ti-che-ski close to it, but still it is not a circle ness. And all the ex-cen-tri-ki (a circle placed on a circle of another ra-di-u-sa with a shifted center), use-use- They are in tech, they move strictly in a circle.

In 1914, the English engineer Harry James Watts figured out how to arrange such a drilling. On the surface he places a right-handed template with a pro-cut in the form of a square, in which a drill moves, inserted into a socket with a “free-floating drill in it.” A patent for such a pa-tron was issued to a company that started manufacturing Watts drills in 1916.

Je-ro-la-mo CARDANO (1501 - 1576). When, in 1541, im-per-ra-tor Charles V tri-um-fal-no entered the Za-vo-e-van-ny Milan, rector of the College of Vra -whose Kar-da-no was walking next to the bal-da-khin. In response to the honor, he offered to equip the royal crew with the weight of two shafts, which were not you-ve-det ka-re-tu from go-ri-zon-tal-no-go po-lo-zhe-niya […]. Justice demands to note that the idea of ​​such a system goes back to antiquity and that at the very least in the “At-lan-ti-che-sky codex” Leo-nar-do da Vin-chi has a ri-su-nok su-do-vo-go com-pa-sa with kar -given under the weight. Such com-pa-sys in the first half of the 16th century, apparently, without influence -I-niya Kar-da-no.

S. G. Gin-di-kin. Talk about physics and ma-te-ma-ti-kah.

We are using another known structure. We attach the drill rigidly to the triangular re-lo, placing it in a square on the right-hand frame . Sam-ma ram-ka fi-si-ru-et-sya on the drill. All that remains now is to transfer the rotation of the drill to the tri-corner of Re-lo.

As a rule, problems with the formation of round holes in metal do not arise. Today you can find a huge number of drills on sale, some can be used to form a square or rectangle. To solve this problem, special devices are also used.

Drill or cutter

Square holes are often obtained by using milling cutters. This type of tool has become extremely widespread, but in some cases it is easier to get square holes in metal using drills. Let's take the following points as an example:

1. The work is rarely carried out, so you need to reduce costs by purchasing special tools. Milling cutters are much more expensive.
2. Small processing area. The geometric shape of common cutters determines the restrictions on their minimum size.
3. You need to get a through hole in metal with a large thickness.

In addition, cutters are installed in machines, which are expensive, but conventional equipment is not suitable for drilling. This is due to the fact that the drill must move along a certain path.

Design and principle of operation

The Watts square hole drill is based on the Reuleaux triangle shape. Among the features are:

1. The working part of the drill is formed by forming an area of ​​intersection of three equal circles of a special shape.
2. If you place several parallel reference lines near the triangles of the working part of the drill, then the distance between them will be the same.
3. During operation, the drill axis must move along a certain path, resulting in a square or rectangle.

It is worth considering that the resulting rectangle or square has slightly rounded corners. Devices for drilling Watts square holes should not limit the movement of the chuck with the drill, otherwise it will not be possible to obtain the shape in question. The operating principles and design of the recommended equipment allow you to create it yourself using scrap materials.

Alternative Methods for Making Square Holes

The production of radius arcs leads to a significant decrease in the quality of the resulting product. That is why the possibility of using other methods for obtaining a square hole is often considered:

1. Laser systems are widely used today. They can be used for processing along a given trajectory; when the beam is focused, the metal is heated, due to which the required surface is formed.
2. The stamping method has been used for a long period. It involves the use of special equipment that is capable of exerting high pressure on sheet and other workpieces. The disadvantage of this method is the high cost of the equipment, as well as the possibility of obtaining only shallow recesses.
3. When using gas welding, it is also possible to form a rectangular shape. However, this technology is characterized by low practicality in application, and the resulting products are of low quality.

There are special sets of punches on sale that can also be used in this case. The kit is represented by a combination of the following elements:

1. Bushing for guiding the punch.
2. Special holder.
3. Ring travel stop.
4. Matrix.

In order to place a high load on the working tool, a hydraulic jack is used. This technology is characterized by the fact that the resulting figure has clean and even edges, that is, additional mechanical processing is not required to improve the quality of the surfaces.