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One of the main types machining cutting of various materials used in modern technology is drilling. It is carried out using a special tool called a drill, which is told rotational movement(in some cases the workpiece rotates). By drilling you can get holes various depths and diameters.

In most cases holes, obtained by drilling, have a cylindrical shape. However, the use of special tools and special processing techniques makes it possible to give them an ellipsoidal, square, curvilinear, oblong, triangular and other shapes.

Oblong holes for fastening GOST 16030 – 70
D	B		L
	1st row	2nd row	3	4	6	8	10	12	14	16	18	20	22	25	28	32	36	40	45	50	55	60	70	80	90	100	110	125
2	2.4	-	×	×	×	×
2.5	2.9	-		×	×	×	×
3	3.4	-		×	×	×	×	×
4	4.5	-			×	×	×	×	×	×
5	5.5	-				×	×	×	×	×	×
6	6.6	7					×	×	×	×	×	×
8	9	10						×	×	×	×	×	×	×	×	×	×	×
10	11	12							×	×	×	×	×	×	×	×	×	×	×
12	13	14								×	×	×	×	×	×	×	×	×	×	×
14	15	16									×	×	×	×	×	×	×	×	×	×	×
16	17	18										×	×	×	×	×	×	×	×	×	×	×
18	19	20											×	×	×	×	×	×	×	×	×	×	×
20	22	24												×	×	×	×	×	×	×	×	×	×	×
22	24	26													×	×	×	×	×	×	×	×	×	×	×
24	26	28														×	×	×	×	×	×	×	×	×	×	×
27	30	32															×	×	×	×	×	×	×	×	×	×	×
30	33	35																×	×	×	×	×	×	×	×	×	×	×
36	39	42																	×	×	×	×	×	×	×	×	×	×
42	45	48																		×	×	×	×	×	×	×	×	×
48	52	56																				×	×	×	×	×	×	×

Square holes for fastening GOST 16030 – 70
	Square size bolt headers	B		R
		1st row	2nd row
	5	5.5	-	0.5
	6	6.6	7	0.5
	8	9	-	0.8
	10	11	12	0.8
	12	13	14	1.0
	14	15	16	1.0
	16	17	18	1.2
	20	22	24	1.2
	22	24	26	1.6
	24	26	28	1.6

Laser processing

In the conditions of modern engineering and any other production, there is often a need to obtain various materials holes having a very complex shape. A method often used for this is to use a laser beam operating in a controlled thermal splitting mode.

Today, laser processing is one of the most advanced methods of forming and processing square, oblong and others holes in a wide variety of materials. This technology allows for high-quality processing, which creates conditions for its larger-scale use.

The use of laser equipment with numerical control allows not only to manufacture or process holes a variety of shapes and configurations, but also to obtain completely finished products.

Electroerosive processing method

In technology, electrical erosion refers to the destruction of the surface of a product or workpiece, which occurs under the influence of electrical discharges.

This processing method is most often used to change, within certain limits, the size and shape of holes previously made in metal products and workpieces. Developers of mechanical engineering products that they design are often faced with the need to manufacture holes that may be different from cylindrical. It can be square, oblong, rectangular, curved and others holes.

It is especially difficult to process them when the material itself has characteristics such as increased hardness or high viscosity. It is in these cases that electrical discharge machining is usually used.

As practice shows, it is most effective for processing products of complex configurations made of hard materials. The fact is that the use of common mechanical methods often results in increased wear of the cutting tool.

Tapered drill bits for drilling sheet metal

In thin sheet metal Quite often you have to do various holes cylindrical shape. This happens, for example, when you need to produce electric installation work in steel boxes, and this is often not so easy to do.

Drilling holes in thin sheet metal using conventional twist drills is not an easy task, since the tool begins to, as they say, “pick up”. This can (and often does) lead to its breakdown, as well as to the fact that the holes are of an irregular, curved shape. Cone drills and step drills cope with this task much better.

The fact is that, thanks to their specific shape, the layer of processed material is cut evenly, without so-called “picking up” and jerking. Therefore, the drilled holes have a perfectly cylindrical shape.

Depending on the exact geometric characteristics of the cutting tool, the use of drills with a conical cutting edge makes it possible to obtain resulting diameters of various sizes. If drilling conditions are particularly difficult, then experienced craftsmen Step drills are used instead of conical ones. This cutting tool allows for very precise dimensions of the resulting holes.

Punching holes

One of the most common technologies for sheet metal stamping is punching. For example, in such high-precision production as instrument making, a very significant number of parts are manufactured using this method. For punching square and oblong holes special equipment is used, made of high-strength materials, resistant to long-term and constant mechanical loads and does not require frequent and thorough maintenance.

Punching holes can be done both on complex mechanized equipment and on simple hand presses. Its procedure is that a workpiece is placed between the punch and the matrix, in which a hole must be punched.

Any hole, if it is made with a drill, has a round shape and in order to make it square, you need to work well with some filing tool. Let's look at how you can drill a square hole in metal with minimal use of a file using the example of making a convenient and reliable tap driver.

In order to make a driver with a square hole for a tap, having a side of 10mm, you will need:
1. Metal rectangular block blank 13mm thick.
2. Electric drill.
3. Kerner.
4. Center drill.
5. Drills for drilling metal with a diameter of 4mm and 9mm.
6. Any coolant.
7. Small triangular file.

The production of the knob is as follows:
1. Make a square of paper with a side of 6mm, mark the center on it and glue it to the workpiece at the place where the hole is drilled.

2. Place the workpiece on a suitable anvil and mark the vertices and center of the glued square on it with a core.

When the paper is removed from the surface of the workpiece, five punched marks remain on it.

3. Fix the workpiece on the surface of the workbench with clamps, having previously placed a wooden plank under it.

4. Use a centering drill to drill all five holes marked on the workpiece.

5. Finally drill four holes in the vertices of the square with a drill having a diameter of 4 mm,

remembering to cool them from time to time a small amount coolant

6. Having reduced the speed of the drill, use a 9mm diameter drill to finally drill the last, fifth hole located in the center of the square, again not forgetting to cool it from time to time.

7. Disassemble the design of the clamps. The result is a crank blank with a drilled square hole.

However, the edges of the hole turn out to be uneven and the tail part of the tap does not “fit” into it.

8. In order for the tap shank to fit completely into the hole, its edges are additionally processed with a file. It is more convenient to do this, of course, by clamping the workpiece in a vice, and the whole work takes no more than 15-20 minutes.

After processing with a file, the square hole in the workpiece becomes smooth, neat, and the tail part of the tap fits completely into it.

How to drill a hole round shape, almost everyone knows, but about the drill for square holes not everyone knows. Meanwhile, you can drill a square-shaped hole both in soft wood products and in harder metal parts. To solve this problem, use special tools and devices, the principle of operation 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 as follows: 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, working on the principle of the Reuleaux triangle, you can drill square holes in metal blanks even on a regular machine that is not equipped with special attachments. In order to create a square hole in wooden part, you can also use a regular drill, but for this it needs to be equipped with additional devices.

Make a simple device that allows you to drill square holes in wooden blanks, you can follow the following recommendations.

• To start, use a sheet of plywood or wooden board small thickness, it is necessary 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 a square with geometric parameters, completely corresponding to the dimensions of the hole 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 operating on the principle cardan shaft truck.
• 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

In some cases, it is necessary to obtain square-shaped holes. Conventional methods inefficient and heavy. 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 in the corners of the square outer surface

describes 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. Technical solution

for the Watts drill was patented in 1916, and a year later mass production of such tools began.

Drill or cutter?

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 more than one cutting plane, as in regular drill, but four, which is 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 mutual 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 clamping fixture with residual speed

(1 – 0.625)f = 0.375f.

The resulting cutter rotation speed can be determined more accurately using technical characteristics drill/hammer, but it is clear that it will be much lower than what the tool was originally designed for. 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. More complex design

1. has an adapter spindle. It includes:
2. Frame.
3. Ring gear. Seat
4. under 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).
5. Drive gear.
6. Main spindle.
7. Meshing gears with a ring gear.

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 communicate eccentric movements cutting tool

. The thickness of this frame determines the depth of the resulting hole.

1. To connect the device to the machine chuck, a special adapter is also required. It consists of:
2. Cases.
3. Floating shank.
4. Swinging ring.
5. Replaceable bushings for cartridges of various metalworking machines.
6. Mounting screws.

Support balls. For practical application

For 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.

//www.youtube.com/watch?v=60WbTPNFT-8

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.. 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 available in household welding inverter a square hole in a steel piece can be burned. 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.