What is a center punch, its types, working methods, photos

Manual and automatic punch A punch or core (German: Körner, core, tap, poke)
is a metalworking tool, shaped like a metal rod, one side of which is sharpened, and the other is prepared for striking with a hammer. Its purpose is to create holes (cores) that make further drilling of the material as convenient as possible. This recess prevents the drill from suddenly slipping when drilling hard metals, even round shapes (pipes) or at an angle.

In its design, the center punch is similar to a punch and punch, but has a pointed end at the end of the working part with an apex angle of 100° - 120°. From the side it resembles a gable roof on a house.

The working part of the punches (cone) is thermally treated over a length of 15 - 30 mm to a hardness of HRC 55 - 59, and the striking part is heat treated over a length of 15 - 25 mm to a hardness of HRC 40 - 45. The middle part of the punch is knurled (knurled) for ease of use .

Punching is done by hitting the hammer on the opposite part of the punch - the buttplate. If each step is strictly followed, the result of the core will be accurate, and the hole will be of the correct shape, which will allow you to drill an even hole in the future. The procedure requires some physical effort and time, which is why modern punches are made mechanical or automatic.

Punching

Formation of pinholes on a workpiece or product

See what “Kerning” is in other dictionaries:

punching - Ndp. core The formation of pinpoint depressions on a workpiece or product. [GOST 18970 84] Inadmissible, non-recommended cores Subjects of equipment. for chipless processing General terms forming operations ... Technical Translator's Guide

kerning - heeling ... Brief dictionary of anagrams

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Contour - Threaded connection is a detachable connection of machine parts using a screw or spiral surface (thread). This compound is the most common due to its many advantages. In the simplest case, to connect you need to tighten... ... Wikipedia

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GOST 18970-84: Metal forming. Forging and stamping operations. Terms and definitions - Terminology GOST 18970 84: Metal forming. Forging and stamping operations. Terms and definitions original document: Cutting (Changed edition, Amendment No. 1). 18. Notching The formation of recesses on the workpiece due to the introduction of... ... Dictionary of terms of normative and technical documentation

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Nacking

After cleaning the ends of the welded holes, the centers of the holes for the threads are marked and punched, a hole of 0 29 mm is drilled and the Briggs thread is cut.  

Any preparation for sawing begins with marking and marking marking marks, drilling holes along marking marks and cutting out armholes for sawing holes in the workpiece.  

Before removing the winding, it is necessary to mark a groove (by punching adjacent teeth), as well as those collector plates to which the ends of the sides of the sections lying in this groove are connected. This is necessary to maintain the same location of the winding in relation to the collector.  

Special punches (Fig. 35a) are used for punching small holes and rounding small radii. The use of such a center punch significantly improves marking quality and productivity.  

Notes about the next test performed are made with indelible paint or marking on all mechanisms and devices used for rigging work.  

A special center punch (Fig. 32, a) is used for punching circles and rounding small radii. A punch of this design greatly speeds up marking and improves its quality due to its increased accuracy.  

When connecting parts with countersunk screws, locking is ensured by capping the part (Fig.  

Leshchev's center punch (Fig. 74, c) is used for punching points at equal distances from each other, as well as for punching points on circles and arcs of small radius from a given center. The center punch consists of a rod to which a spring leg is attached and an adjusting screw. By rotating the screw, you set the angle of the arc being marked or the step between the points that should be marked. The tip of the leg is placed at a given point and the marked point is punched with a hammer on the end of the eraser/cue.  

Special punches (Fig. 35, a) are used for punching small holes and rounding small radii. The use of such a center punch significantly improves marking quality and productivity.  

To determine the position of centers on the ends of small processed workpieces and simultaneously mark them, special devices called center markers are used. The marking consists of placing the center finder with a funnel on the end of the part, checking its installation by eye, and then hitting the punch head with a hammer. At the end of the part, a center is outlined.  

During routine repairs, reduction of the increased gap is temporarily achieved by spreading the rings by punching both ends of them (Fig. 103) to a depth determined by experience.  

Locking through local plastic deformation is carried out after tightening the screw or nut by punching (Fig. The operation of punching bolts or studs is much faster by using a special punch fixed on the nut (Fig.  

Device and characteristics

As mentioned above, the device is made in the form of a cylindrical rod.

One side is prepared for striking with a hammer, it is called a striker or butt plate, the other is sharpened in the shape of a cone, and the sharpening angle is 120 degrees.

The procedure requires some physical effort and time, which is why modern punches are made mechanical or automatic.

The design of a mechanical tool is based on the tight compression of a spring built inside and its subsequent release.

The impact on the butt plate is carried out due to the cocking and trigger mechanism.

In this case, a hammer is not required for applying cores.

In an electric automatic device, work is started due to the action of an electrical circuit built inside the punch.

Moreover, the process takes little time and in one minute the master is able to make at least 50 holes.

Marriage during marking

First of all, when marking, defects that were made at previous stages of production emerge. Products from procurement sites or workshops, as well as materials purchased from other enterprises, reveal:

• violation of dimensions
• shape distortion
• warping.

Such castings or rentals are not subject to further marking operations, but are returned to the department or organization that caused the defect to correct it.

At the marking stage itself, defects can be caused by the following factors:

• Inaccurate drawing. The mechanic, without hesitation, displays incorrect dimensions on the part, and during further processing, defective products come out.
• Inaccuracy or malfunction of instruments. All marking tools are subject to mandatory periodic verification by the metrological service of the enterprise or an authorized metrological center.
• Incorrect use of tools or marking accessories. There are known cases when instead of calibrated measuring pads, ordinary pads were used to set the level. In this case, erroneous application of angles and slopes is also possible.
• Inaccurate placement of the workpiece on the marking table or plaza. They lead to distortions when setting aside dimensions, violation of parallelism and coaxiality.
• Wrong choice of reference planes. It is also possible that some of the dimensions were applied from the base planes, and some from the rough surfaces of the workpiece.

Marriage during marking

Separately among the reasons for defects are the marker's errors. These include:

• Incorrectly read drawing. It is possible to apply a radius instead of a diameter and vice versa, inaccurate application of the centers of holes relative to the center marks, etc. If any difficulties arise, the mechanic must seek clarification from the foreman or foreman.
• Carelessness and inattention when punching and drawing lines.

Negligence can be committed by both the mechanic himself and his supervisors, who did not check the tool on time or issued inappropriate marking devices.

Typically, marking operations are entrusted to the most experienced and responsible workers, counting on the fact that they will not mechanically transfer dimensions from the drawing to the workpiece, but will treat the matter thoughtfully and promptly notice and eliminate the reasons for possible defects on their own or by contacting their managers.

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A punch is a metalworking tool, shaped like a metal rod, one side of which is sharpened, and the other is prepared for striking with a hammer.

This tool is also called a core; its purpose is to create holes that make further drilling of the material as convenient as possible.

This recess prevents the drill from suddenly slipping and ensures that the hole is created in the desired location.

Types of core samples and their purpose

Types of core differ in their operating principle and main purpose. In the arsenal of locksmiths you can find the following types:

Manual locksmith

Designed for working with metal, tiles, and other types of polished or smooth surfaces.

Center punch compass

It differs from the classic version in that it allows you to make holes at a preset distance.

Kerner bell

Used for punching surfaces shaped like a ball.

What you need to know about the center punch

When choosing a core sample, you need to remember several important points about this type of instrument.

Firstly, it does not matter at all what cross-sectional shape the tool rod has.

It is much more important to pay attention to its other characteristics.

Secondly, you should buy a device based on the diameter and type of drill with which it will be used.

Thirdly, if you plan to use a center punch when working with soft metals, it is better to choose one with a smaller sharpening angle and vice versa.

Electric sharpener

To make work easier when sharpening tools, there are various electric sharpeners and sharpening machines.

Choosing an electric sharpener is extremely simple. Such a machine consists of an asynchronous motor (such motors are perfectly mastered by industry), grinding wheels (they are replaceable and can be changed with a wrench) and casings. If the sharpener is not taken for industrial use, then the brand does not matter so much. Such equipment is turned on for a short time, and its resource will be consumed extremely slowly - even an inexpensive machine will last for many years.

The diameter of the wheel directly affects the price of the sharpener, so an amateur craftsman or small enterprise should not chase larger diameters.

When inspecting the electric sharpener before purchasing, try moving the shaft. If it not only rotates, but also walks, then you have a marriage. Spin the stone with your hand and look at the free end of the shaft, does it vibrate? It is best, of course, to turn on the sharpener, but not all stores allow you to do this.

How to use a center punch

Like any other professional tool, all types of center punches require compliance with certain rules for working with them.

Only in this case can we guarantee the best results and safe operation.

While there are ways to rework an incorrect core, they will require more skill than the original hole punching.

Basic Rules

In order to correctly perform the procedure for working with any type of punch, you need:

1. Markings are applied to the material on which holes need to be made.

2. The striking part of the center punch is aligned with the intersection of the marking line.

3. After this, the device is installed strictly perpendicular to the material.

4. Depending on the type of device, impact is applied (with a hammer, using a trigger mechanism or other available method).

If each step is strictly followed, the result of the core will be accurate, and the hole will be of the correct shape, which will allow you to drill an even hole in the future.

Mark. We drill where we need to!

Anyone who has ever tried to drill into solid surfaces knows how difficult it is to make a hole exactly in the intended location.
The drill tries to slide at least a little to the side. I have to try again several times. But if there is already at least a small hole in the right place, the process goes much faster. But how to do it? For this purpose, a special core tool was invented, also known as a center punch. A conventional core tool consists of one piece - a strong steel rod. This can be U8 steel, hardened to 65 HRG and tempered. Chrome-vanadium alloy or other durable types are used. One end is sharpened in the form of a cone, the other is flat. The rod itself can be seven-sided or round. The length of the center punch ranges from 10 to 16 cm, thickness - 0.8-1.2 cm.

The process of marking cores (holes for installing a drill) goes like this. Hold it with your left hand. The sharp end of the tool is placed at the location of the intended hole. With the right hand, a precise blow is applied with a hammer to the butt plate (flat part). A mark from the punch (core) appears on the surface being processed. This word should not be confused with the concept in geology, where it refers to rock obtained by drilling.

To prevent the hand from sliding over the tool during operation, the cylindrical surface is covered with special notches or knurling. The conical (working) part is sharpened at a certain angle. The sharper it is, the higher the marking accuracy. A core with a sharpening of 30-45° marks the centers of circles, 75° is used when marking a hole for a drill.

There is no point in sharpening the core with emery, since its material cannot be processed in such a way.

How to choose the right core

To choose the most suitable type of device for yourself, you need to be guided by two factors: your own financial capabilities, the purpose of purchasing the device.

The cheapest type is a regular bench punch, which will be sufficient if you plan to use it in rare cases.

The most expensive type is the electric automatic center punch.

It, as well as mechanized types, are purchased by professional mechanics for daily work.

How to make a core with your own hands

You can make the simplest type of tool yourself, using a hexagon as a basis.

At the same time, its striking part is ground, and the tip is sharpened with a certain amount of coal, after which the tool is hardened on both sides.

A regular gas stove is suitable for hardening.

The metal needs to be heated to a bright pink color, and then placed in water for a few seconds, pulled out, and immediately lowered again, but holding the tool in the water a little longer.

This simple type of device is quite suitable for home repairs, and its production will take no more than an hour.

Kerner rating

The most famous manufacturers of professional and semi-professional tools offer to purchase a center punch from them.

The highest positions in the ranking are occupied by:

• HAUPA company, whose core is said to be comfortable for the hands and made of high-quality impact-resistant steel;

• RENNSTEIG company – the only drawback is the overpriced;

• TOREX company – traditionally producing strong tools.

• KRAFTOOL company – produces high-quality products.

By choosing a punch from a well-known manufacturer, you can guarantee its long service life and safety in use.

Source

Literature[ | ]

• Kerner, instrument // Encyclopedic Dictionary of Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg, 1890-1907.
• Kerno // Encyclopedic Dictionary of Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg, 1890-1907.
• GOST 7213-72 “Core punches. Technical specifications"
• Kerner // Commodity dictionary / I. A. Pugachev (editor-in-chief). - M.: State Publishing House of Trade Literature, 1957. - T. III. - Stb. 477

Techniques for working with a center punch

There are only two ways of punching: one is correct, the second is incorrect.

For core you need:

That's all, failure to follow these rules will lead to a violation of the accuracy of the core or the shape of the hole, which may cause the drill to move away.

If you made a mistake when punching, then do what no plumbing textbook will advise you to do:

How to make a punch with your own hands

For those who do not want to pay 300 - 500 hard-earned rubles for a center punch of more or less normal quality, there are several options for making this tool on your own. We have already mentioned the first one - from a hexagon.

You can also quickly make a primitive, but quite workable center punch from an old drill whose side edges have lost their functionality, and therefore cannot be sharpened, by simply sharpening its end.

However, we still do not recommend using such a tool in its pure form - it is very fragile and can break upon impact and cause injury. As a last resort, put a piece of high-pressure hose on it, as in the version in the photo, but better - select a metal sleeve from a tube of suitable diameter or grind it.

In addition to the options mentioned, there is a way to make a center punch from almost any steel, but only carbon steel can be hardened. If you are not sure about the carbon content in it, then you can check this by sparking when processed on a grindstone. And here is the video:

And if you did not see the long-awaited stars when sharpening a suitable rod for making a center punch, then you can carry out the cementation process, which we mentioned at the beginning of the article. There are two ways to do this at home. If you have a welding machine on your farm, then the one shown in the video is the most acceptable and simple.

And if purchasing a welding machine is still in your plans, then look for a nearby metalworking plant where they sharpen cast iron parts and collect cast iron shavings, the smaller the better.

Or buy cast iron powder online. Having heated the metal to the same bright pink glow, lower the part of the workpiece that needs to be quenched into cast iron shavings. The carbon from the cast iron will move into the surface layer of your mild steel and allow it to harden.

The procedure can be repeated several times, but sharpen the center punch before it. However, the instrument can be repaired in the future in the same way.

Dear readers, if you have any questions, please ask them using the form below. We will be glad to communicate with you

Source

Automatic center punch – user choice

SKRAB 26291

Advantages and disadvantages

convenience

good impact force

Marks weakly on thick metal

BISON Expert 21420-10

Professional automatic center punch, used for precise marking of parts when drilling. High quality and fast execution of work.

Advantages and disadvantages

price quality

light weight and size

tip made of durable steel

no significant

Kraftool 21425-12

Designed for marking metal and non-metallic materials.

Advantages and disadvantages

price quality

comfortable

impact force adjustment

tip made of durable steel

no significant

RENNSTEIG RE-430230

Advantages and disadvantages

good quality

pressure stop

replacement pin

nothing significant, except for the price

What is a punch, its types and purpose

Any metalworking operation is preceded by marking the part with lines and reference points deepened into the surface of the metal. The first ones are done with scribers, and for applying the second ones there is a special marking tool - a center punch. In general form, it is a small metal cylinder with a sharpened working end and a flat back. GOST punches are made of rolled rods of alloy and carbon tool steels. In conventional punches, the marking point (core) is applied by hitting a hammer, while in mechanical automatic punches a spring and a striker are used for these purposes.

Application

First of all, a center punch is used to make indentations (cores) on pre-marked lines. Cores are made so that the marks are clearly visible and are not erased during the processing of the part.

In addition to marking, the center punch is also used to lock (prevent unwinding) threaded connections.
To do this, place one to three core holes in the gap between the threads of the screw and the nut or along the edges of the slot of a countersunk screw. The deformation of the metal that occurs upon impact is sufficient for locking, but allows the threaded connection to be unscrewed using a conventional tool. Another area of ​​use for center punches is impact-point marking. Coding of parts is mandatory for their subsequent processing and identification in assembly production. Usually, specialized pneumatic and electric machines are used for this, but for single production in small volumes, it is quite possible to get by with an automatic mechanical punch.

Applying markings using a center punch

What is a center punch and what is it for?

A center punch or core (German Körner - “tap, poke”) is a hand-held metalworking, impact-cutting tool designed for marking central holes (cores) for the initial installation of a drill and other visual markings. A center punch can be classified as a metalworking tool, since holes for drilling are usually made on metal, tile, polished or any other smooth surface.

Using a punch allows you to avoid the drill from slipping through the material and helps to achieve greater precision in the location of holes. Externally, the center punch is a round rod.

At the beginning of the tool there is a striker (impact part), at the end there is a pointed cone, the middle part of the tool, as a rule, has stripes, notches, knurling or corrugation for better grip. The working part of the cone - the pointed end is sharpened to an angle of 60° or 90° (this angle is called the sharpening angle of the center punch).

Punch punches are manufactured in two versions: with a rounded impact end or with a chamfered impact end. The punches are made from tool alloy steel grades 7ХФ and 8ХФ in accordance with GOST 5950-2000, from tool carbon steel grades U7A and U8A in accordance with GOST 1435-99, or from steel of other grades with mechanical properties in a heat-treated state not lower than the specified steels. The hardness of the working part of the punch should be 54.5...58 HRCe for steel grades U7A and U8A and 56...60 HRCe for steel grades 7ХФ and 8ХФ. The hardness of the impact part should be 36.5...41.5 HRCe and 41.5...46.5 HRCe, respectively.

If the material is soft and the thickness of the workpiece is small, then you can make holes with a center punch - you just need to hit it with more force. But in other cases it is better to use a tool specially designed for this purpose.

Types of cores

In addition to the manual version of this tool, there are other varieties of it.

Basic Rules

In order to correctly perform the procedure for working with any type of punch, you need:

If each step is strictly followed, the result of the core will be accurate, and the hole will be of the correct shape, which will allow you to drill an even hole in the future.

How to make a core with your own hands

You can make the simplest type of tool yourself, using a hexagon as a basis.

At the same time, its striking part is ground, and the tip is sharpened to a certain angle (about 60 degrees), after which the tool is hardened on both sides.

A regular gas stove is suitable for hardening.

The metal needs to be heated to a bright pink color, and then placed in water for a few seconds, pulled out, and immediately lowered again, but holding the tool in the water a little longer.

This simple type of device is quite suitable for home repairs, and its production will take no more than an hour.

Source

Tool classification

The center punch is designed to create small conical recesses on the metal surface using a pointed end, which, in accordance with GOST, must be sharpened at an angle of 60÷90º. The principle of operation of all punching tools is the same: the tip deepens into the marked material when hitting the rear end of the rod, and the force applied depends on the hardness of the workpiece. The main differences between individual types of punches are the methods of striking and holding the rod in a given position. First of all, a distinction is made between conventional manual and automatic punches. The latter, in turn, are divided into mechanical devices with manual drive and installations with pneumatic and electric hammers. In addition to devices for punching with manual holding of the rod in the required position, tools are produced with automatic installation of the tip in the desired location and at a given angle. This includes transfer and self-centering punches. In addition, there are a number of devices for punching, supplemented with special equipment (magnifying glasses, compasses, etc.). Devices for impact-point marking, which are essentially automatic punches for special purposes, are usually classified into a separate group.

Manual punch

Unlike an automatic marking tool, which is a prefabricated product, a conventional manual punch is a monolithic metal rod and consists of four functional parts (see figure below):

1. Impact end. In accordance with GOST, it can be round or, as in the figure, with a chamfer. The tool is considered unsuitable for use when a rivet appears at the end of the impact end.
2. Lever. The length of the handle according to GOST must be at least 35% of the total length of the punch. For reliable retention, corrugation must be applied to its surface (this also applies to automatic devices).
3. Conical part.
4. Point. According to the standard, the tip should be sharpened at an angle of 60º. But for more precise marking, you can use a sharpening angle of up to 30º, and for marking centers for drilling - up to 75º. The requirements for this part do not depend on the type of marking tool and are the same for both conventional manual punches and automatic ones.

Automatic center punch

Among automatic punches, the most common are manual mechanical ones, which allow you to apply markings with one hand. Most of them use a Sweet mechanism with an intermediate pusher, and only high-force industrial models use other types of mechanisms without pushers. The body of a typical automatic mechanical punch consists of three parts (see figure below). This design was chosen solely for the convenience of its manufacture, as well as assembly and disassembly of the tool.

Inside the body of the automatic center punch there are:

• a working spring, which, when straightened, forms a shock impulse;
• a massive striker with a recess on the front part, whose depth determines the working stroke of the tip;
• a pusher that serves to cock the device and transmit impulse to the rod;
• a pointed rod made of carbide, the tip of which creates a core depression.

The working cycle of the mechanism of this automatic device includes three stages (see figure below):

1. The sharp end of the rod is installed according to the markings. At this time, the pusher, due to the shape of the front surface of its cap, is in a slightly skewed state and rests its upper end against the edge of the striker. When the body is moved downwards by manual force, the working spring is compressed.
2. At the top point, when the spring is fully compressed, the pusher moves from a lateral to an axial position, occupying a place directly opposite the recess in the striker. This is a key feature of this automatic mechanism, for which its inventor received a patent.
3. The upper part of the pusher passes into a recess in the striker, the spring is free to move and transmits the accumulated impulse through the striker and pusher to the pointed rod. Since the body of the automatic center punch continues to be held by the mechanic’s hand, all the kinetic energy of the striker will be directed toward breaking through the core hole.

The meaning of the word "kernel"

put on

1. tech. apply cores ◆ If it is necessary to core

a lot of holes. Make a groove in a wooden block and use rubber bands to clamp the center punch into it. Nikolay Zvonarev, “Home Locksmith”, 2009

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