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The principle of operation of the automatic core. Homemade puncher. Types of punches - photo

If, among professionals, someone called this tool a core, it ceased to be such by definition. A core or core is a hole in the material - the result of the work of a center punch and nothing else. And also a sample of the soil rock, obtained in a special way, but this is definitely not the subject of our article. Now, even Wikipedia gives the word "core" as the second name of the tool - the center punch, which is fundamentally wrong, but let's leave it to the conscience of the authors of the material.

The center punch is a metal rod made of tool steel with a pointed impact part, sharpened at an angle of mainly 120 ° and hardened to a length of 20–30 mm, and a striker, on the other hand, also heat-treated, but by 10–15 mm. It is also called a butt pad. It is used in plumbing to obtain holes or cores necessary for the convenience of drilling material.

Most of the tool remains non-hardened, and therefore less fragile, which is done primarily for the purpose of its safe use. The cross-sectional shape of the center punch rod does not play a special role: it can be round, and then knurling is often done on it, so that it is more convenient to hold it in your hand, or maybe hexagonal. The material of the hexagons is heat-treatable carbon steel, so if you need to quickly make a center punch at home and find a suitable hexagon in cross section, you can safely use it - it will accept hardening without carburizing (saturation of the surface layer of steel with carbon).

Piercing, in almost all cases, is performed for subsequent drilling of the material so that the drill does not slide on the surface of the workpiece for initial stage drilling. But there are options...

Depending on the diameter of the drill, the dimensions of the center punch are also selected, but this is more often the case in production during mass punching, to obtain holes of different diameters.

Also, the angle of sharpening the center punch may be different, because for soft metals the drill is sharpened at a smaller angle.

How to work with a puncher

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

For punching you need:

  1. Align the tip of the striker with the intersection of the marking lines;
  2. Set the punch strictly perpendicular to the surface of the workpiece;
  3. Apply one confident, accurate hammer blow to the striker, trying to make the blow vector coincide with the center punch axis.

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

If you made a mistake when corening, then do what you will not be advised in any plumbing textbook:

  1. Gently, with light blows of a hammer, settle the edges of the core funnel to the level of the workpiece, if necessary, process this place with an emery cloth fixed on a flat bar;
  2. Resume marking lines;
  3. Take a smaller diameter punch with a sharpening angle of about 60 ° (for such cases, you need to keep it in your home workshop);
  4. Perform the punching procedure with extreme care, but with less impact force;
  5. After making sure that the location of the new core is accurate, take a standard center punch and, aligning its tip with the new hole, one with a strong blow make a punch.

Types of punches - photo

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

  1. Center punch compass, in addition to a clear punching in a circle from a given (and also punched) center, it allows punching at a predetermined distance from the edge of the workpiece, which is convenient if there should be a lot of such cores. In addition, the leg can be changed to a simple extension device and, again, set aside the desired distance from the edge, reducing the number of marking lines.
  2. Punch bell designed primarily for punching spherical surfaces. Installed on a ball, it will perfectly self-install on its top, which is why it is also called a center finder. The base line can serve as a circle outlined by his skirt. Also, with the help of a center finder, it is easy to core the centers of the ends of cylindrical figures, of course, if the diameters are suitable.
  3. Mechanical spring punch allows punching with one hand, it is only important to set it strictly perpendicular and not change this position when pressed. Among its advantages is also the same depth of the obtained cores. And the ability to adjust the force makes it possible to work even with fragile or soft materials without fear of damaging them.

The factor of a clear increase in the speed of the core is also important.

4. In an electric punch the induction coil retracts the spring-loaded striker. Everything else is very similar to the mechanical version of the tool.

How to make a do-it-yourself punch

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

To make a simple center punch from this material, it is enough to grind its impact part, sharpen its tip at a given angle and harden it and the striker. And you can do it even on a regular gas stove, heating the metal to a bright pink glow. Although it is much faster to do this with gas burner or a gasoline blowtorch, which we hope you already have in your workshop.

The heated metal must be lowered for 4-5 seconds. into the water, then for 1 sec. remove and re-lower another 10 -15. If you perform the same procedures, but dipping the tool in oil, burnishing will occur, which is even better.

You can also quickly make a primitive, but fully functional center punch from an old drill that has lost its lateral edges, and therefore cannot be sharpened, by simply sharpening its end.

True, we still do not recommend using such a tool in its pure form - it is very fragile and can break and cause injury upon impact. In extreme cases, put a piece of hose on it high pressure, as in the version in the photo, but better - pick up a metal sleeve from a tube of a suitable diameter or machine 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 it by a spark when processing on a grindstone. And here is the video:

And if you did not see the long-awaited stars when sharpening a suitable bar 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 the farm, then the one shown in the video is the most acceptable and simple.

What if the purchase welding machine still in the plans, then look for a metalworking plant nearby, where cast iron parts are sharpened and collect cast iron shavings, the finer 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 hardened into cast iron chips. The carbon from the cast iron will move into the surface layer of your mild steel and make it hardenable.

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

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

Anyone who has ever tried to drill solid surfaces knows how difficult it is to make a hole exactly in the intended place. The drill tends to slip at least a little to the side. You 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 make it? For this, a special core tool was invented, it is also a center punch.

A conventional core tool consists of one piece - a strong steel rod. It 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 is seven-sided or rounded. The length of the punch ranges from 10 to 16 cm, the thickness is 0.8-1.2 cm.

The process of marking cores (holes for installing a drill) occurs as follows. Hold it with your left hand. The sharp end of the tool is installed in the place of the intended hole. With the right hand, a precise blow is applied with a hammer on the butt plate (flat part). On the processed surface there is a trace from a center punch (core). This word should not be confused with the concept in geology, where it refers to the rock produced by drilling.

To prevent the hand from slipping 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 basting a hole for a drill.

It does not make sense to sharpen the core with emery, since its material cannot be processed in such a way.

Application

With the help of a core, you can make a mark on any surface. It is advisable to use it when working with smooth materials. These are tiles, polished surfaces. Most often it is used when drilling metal. Therefore, core is more often referred to as metalwork tools.

It is also actively used by masons. For this, special masons' punches have been created. They are not much different from locksmiths. They are often powder coated bright color to make it easier to find if lost.

Cores are also used to make processing lines visible. To do this, the applied markings are passed with frequent cores, making it dotted.

What are there?

  • manual;
  • automatic;
  • electrical;
  • with special features (center finder for coring on cylindrical or spherical parts, a device for marking at the desired distance from the edge of the workpiece).

The automatic punch allows you to:

  • mark with one hand;
  • work without a hammer;
  • adjust the force when working with delicate materials;
  • get marks of the same depth;
  • get the job done faster.

An automatic core allows you to make up to 50 strokes per minute at a distance of 2 cm between the holes.

Instead of a core point, a brand can be inserted into the rod and parts can be stamped.

An automatic (mechanical) core looks a bit like a metal fountain pen. It consists of two chambers, each of which has its own striker. The first is made in the form of a cut cone. There is a shock striker, which will apply cores to the surface. Behind it is a spring-impact striker with a guide rod. Its spring is slightly offset to the side.

Behind it inside the case there is a through hole. In the second chamber, a piston with a beveled edge spring-loaded with a powerful spring.

When the instrument is placed on a surface and the thumb right hand press the stop cap, the impact striker rests against the edge of the spring-loaded piston, lifting it. The spring behind it is compressed and creates a counter pressure.

At the end of the compression process, centering and alignment takes place towards the primary chamber. This leads to the fact that the stem breaks and falls sharply into the hole.

The spring pressure is transmitted through the intermediate elements to the striker. It hits the surface of the material, and a hole from the automatic center punch remains on it.

In some models, the lower head can be changed, thus extending the life of the tool.

The impact force of the automatic core can be changed by turning the stop cap on the top of the tool. In this case, the spring under it is weakened or compressed. The minimum impact force is 10 kg, the maximum is 15 kg. Hole depth from 0.2 to 0.3 mm.

Electric core

In electric punches inside the case there is an electromagnet coil, a tip, a spring and a striker. After pressing the body, it lowers, the washer of the tip, which does not move at this time, closes the electromagnet circuit. The impact occurs when the solenoid retracts the ferromagnetic striker. It strikes the tip, leaving a mark on the surface.

Which core to choose?

A simple core is the cheapest, an electric one is much more expensive. When choosing a tool for yourself, decide how often you are going to use it. If only occasionally, then a conventional or inexpensive automatic is enough (so that you can do without a hammer). For professional activities, they buy high-quality mechanical or electrical.

If you have car valves lying around at home, do not rush to throw them away!

I want to tell you how you can make an excellent core from a valve with your own hands, which will work no worse than the factory one, and it will not look bad at all.

Only the inlet valve needs to be used, as it is completely one-piece and does not have a cavity inside like the exhaust valve.

Materials and tools

To make a core, we need:
  • intake valve from any car;
  • screwdriver or drill;
  • grinder or emery;
  • heat-shrink tubing.

Manufacturing

Clamp the valve in a vise and cut off the cap.



After the cap has been cut off, we clamp the valve into a screwdriver or drill in order to sharpen the end of the workpiece with a grinder or emery.

In extreme cases, this can be done by holding the valve with your hands, while not forgetting about safety.



Now I clamp the valve into the screwdriver from the back and clean the entire surface.


I sharpened the valve from the side of the cap and you should get it as in the picture.


Then, with the help of a burner, a technical hair dryer or a lighter, I upset the heat shrink tube.


Now our core has a beautiful appearance and is completely ready for work.

Core check

And to check how the core works, I will be on a steel strip 2.5 mm thick.



The core does its job perfectly and, as you can see in the photo, the tip is absolutely not blunt.

Video from the author of homemade


Good luck to everyone, and the implementation of all plans.

Hello.

In today's review, we will talk about an automatic center punch that I purchased on eBay. If suddenly you decide to drill hard metal or material with a smooth, even surface, then the drill may slip off the intended point, leaving behind a fairly decent scratch. To avoid such situations, a center punch is used, which makes a small depression (hole) in the surface of the material being processed. As a rule, a punch is a metal rod made of carbide steel. One end of it is pointed, and on the other "butt". We put the tip in the place where we need to drill a hole - we hit the "butt" with a hammer and the hole is ready. It’s simple, but not always convenient, since, firstly, you need to use both hands, and, secondly, to constantly carry a hammer with you is also a so-so prospect. In order to simplify the process, an automatic center punch was created. But first things first.

So, this product was ordered a long time ago, however, I only got around to writing a review just now. But during this time I managed to check the tool in almost all possible situations and so far nothing has broken, which is good news :) If you are interested, you can see the route of the package from China to Belarus.

A live punch is not much different from what can be seen on the seller's page and looks like this:


In addition to the appearance, the seller’s page also has core characteristics:

Material: High speed steel material HSS, Hardness up to HRC58 - 60;
Color: gold + red;
Total length: about 125mm.;
Style: conical;
Usage: industrial;
Load type: compression;
Red ball-shaped plastic handle for shock absorption, good for hand grip;
Can be used for marking, punching, scoring and scribing on wood, metal and plastic, can also be used to break glass.

This tool also has a more budget variation - without a red plastic handle. It just seems to me that because of the rather stiff spring, it will not be very convenient to use them. So it's better not to save here, especially since this performance cannot be called expensive.

The total length of the core is 128 millimeters.


The diameter of the brass handle is 11.5 millimeters. The handle is covered with a grooved pattern, so that the core does not slip at all even in a wet hand. So they are equally comfortable to use even in the rain, even after swimming in an oil bath :)


The diameter of the needle is almost 4 millimeters.


So his dimensions not so big, and given the weight of only 77 grams, the core can be considered more than a compact tool (given that a hammer is not required to use it). It can easily fit in a pocket or small bag, which improves mobility while working on, say, rooftops or other challenging environments.

Despite their apparent simplicity, core devices can hardly be called elementary. There are 8 pieces in total.


To simplify the perception of how it works, I will give a diagram of the device of such a tool:


To put it simply, in order to pinch the hole, you need to put the needle at the right point and press the core from above, at a certain moment there will be a click and the tool will do its job. It works by compressing and then abruptly releasing the shock spring, which sets the striker in motion, striking the counterpart and then the needle.

A bias spring is installed on the counterpart of the side resting against the needle, which compresses under load.


Due to the fact that on the one hand its diameter is narrower, and on the other it is wider - the movement of the counterpart of the striker occurs with an offset relative to the center. That is, roughly speaking, its shank rests against the edge of the striker.
In the striker, in turn, on the one hand there is a hole that acts as a trigger mechanism.


At a certain moment, the shank of the impact part is centered and falls into this hole.


The load applied to the striker from the side of the needle disappears and the shock spring does its job - releasing abruptly, the striker strikes the counterpart, and that, in turn, strikes the needle, which is why the mark is obtained.

The shock spring is located under the red plastic part so that it can be used to adjust the force of the shock, which is important.


In principle, there is nothing more interesting and useful as in appearance, and this tool is not in the device, which means you can proceed to its practical tests.

For starters, a Soviet-era hammer was used as a test subject:


"Holes" on closer inspection:


As you can see, they are all neat, approximately the same both in diameter and in depth. And, most importantly, one mark takes 1-1.5 seconds, no more.

Duralumin:


For fun, I tried it on a regular board :):


It didn’t break through, but the marks are more than decent.

And here is a short video on how it all looks live (I immediately apologize for focusing - my camera cannot focus the way I would like, but the essence of the process is clear):


Summing up everything that was written here, I can say that the instrument met all the expectations placed on it. In operation, it is trouble-free, besides, using an automatic core is much more convenient and faster than a conventional one. True, at first the center punch sometimes stuck and had to disassemble and assemble the impact part in order to restart the process. The installation of an eccentric spring on the contrary helped to get rid of this problem. So if you have to make holes in hard steels, ceramic tiles etc., then you can consider this product as an upcoming purchase. It is not expensive, but at the same time it will really reduce the time of work and the integrity of the surface of the processed material.

On this, perhaps, everything. Thank you for your attention and your time.

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