When trying to drill a smooth surface, the drill often slips to the side, leaving deep scratches and spoiling the workpiece, unless a guide hole is first created. Kerner solves this problem by ensuring the cutting tool is positioned accurately and preventing it from moving away from the intended axis. This simple, but indispensable in metalworking and auto repair tool allows you to form a conical depression that reliably fixes the nozzle of the drill at the beginning of rotation.
The use of a corer is critically important when working with solid alloys, where the slipping of the drill can lead not only to the defect of the part, but also to the breakdown of an expensive tool or injury to the master. Accuracy of markup It depends on the quality of the performed kernation, since even a minimal displacement of the center of the hole can make it impossible to further assembly of the node. That is why understanding how to choose and use this tool is a basic skill for any metalworker.
In automotive business, kernification is often required in the repair of body elements, the manufacture of brackets or the restoration of threaded joints, where the holes must be drilled strictly according to the drawing. Incorrect use of the tool or its absence leads to the fact that the holes are skewed, and the fastening bolts do not fall into their places. Consider in detail the design features, varieties and technology of working with the corer to exclude typical errors.
Design features and principle of work
Classic corer is a steel rod made of instrumental alloy steel, which has undergone special heat treatment. The working part of the tool has a conical shape with a sharpening angle, which is standardized to ensure optimal implementation into the metal without excessive flattening of the edges of the hole. Tails The corer is usually performed with a notch or riff to prevent the hammer from slipping at the time of impact and to ensure maximum force is transmitted.
The principle of operation is based on the creation of plastic deformation of the metal at the point of contact. When a hammer strikes the corer's buckle, the pressure at the contact point reaches values exceeding the yield limit of the workpiece material, which leads to the formation of a funnel-like depression. Geometry of the well It should perfectly match the shape of the cross-section of the drill, which guarantees its centering. If the angle of sharpening of the corer is less than the angle at the top of the drill, then during drilling there will remain undisturbed areas that will quickly dull the tool.
Modern models can be equipped with additional elements that increase comfort and safety. For example, some corers have a spring-loaded mechanism that allows one-handed kernitting without using a hammer. Such kernel It is especially convenient when working in hard-to-reach places or when you need to perform many holes in a short time, saving the power of the master.
⚠️ Warning: Never use a corer with a blunted or damaged point, as this will result in a wide and shallow hole that will not be able to hold the drill.
The main types of corers and their purpose
Depending on the tasks performed and the specifics of the work, corers are classified into several main types, each of which has its own design features. Standard corer 60 degree sharpening angle is a versatile tool used to mark places for future drilling holes. This angle is considered optimal for most spiral drills, providing reliable fixation and the right direction.
For more accurate marking, especially if you need to transfer dimensions from the drawing or template, use corers with a sharpening angle of 90 degrees. They call them. markingThey allow you to make very small, barely noticeable points that are easy to fix in case of error. Such corers are often used in the initial stages of marking, before deepening the mark with a 60-degree angle for direct drilling.
- 🔨 Shock corer - a classic tool that requires the use of a locksmith for applying a label.
- ⚙️ Automatic corer - equipped with an internal mechanism with a spring that works when pressing the end.
- 📐 Electromechanical kerner It operates from batteries or batteries, creating vibration or impact to precisely set the point.
- 🎯 Kerner Center - used to center parts when installed in a lathe cartridge or on a rotating center.
A separate group consists of specialized corers designed for specific operations. For example, corers for punching holes in sheet metal have a flat working part and are used in pair with a matrix. Automotive repairs are also available. pipe-cournerThey allow for the sliding of round surfaces without slipping.
Technology of correct metal kirning
The kerning process requires a certain sequence of actions to achieve maximum accuracy. First, the surface of the workpiece is cleaned of dirt, oil and rust, after which the marking of the places of future holes is made using a drafting machine, ruler and coal mine. Crossing the risqué is the center of the future hole, and it is at this point that the corer tip should be installed.
To improve accuracy, it is recommended to first make a light notch, holding the corer at an angle of about 60-70 degrees to the surface to better see the point of hit. Making sure that the tip got exactly in the center of the intersection of the lines, the tool is transferred to a perpendicular position and a confident blow is applied with a hammer. The impact strength depends on the hardness of the material: for soft metals (aluminum, copper), the impact should be easier than for steel.
When working with large parts or if necessary high accuracy, the kerner is held with the left hand, tightly pressing the thumb and index fingers, and the remaining fingers rest on the surface of the part for stability. This allows you to control the verticality of the instrument and feel the moment of contact. After the impact, you need to visually check the result: the hole should be clear, symmetrical and located strictly at the intersection of marking lines.
☑️ Checklist before starting work
Rules for sharpening and restoring the tool
During operation, the working part of the corer gradually dulls, deforms or even crepts, which requires timely restoration. Kearner sharpening is made on an abrasive circle (sharpening machine) or manually with a file, while it is necessary to strictly observe the angle at the top. For standard work, this angle is 60 degrees, which corresponds to the angle of sharpening of most drills.
When sharpening on the machine, it is important not to overheat the metal, so the tool should be periodically cooled in a container with water or oil. Overheating can lead to steel release, and the tip will become too soft, starting to quickly blunt at the first strokes. A properly sharpened corer has a symmetrical conical shape, and its axis coincides with the axis of the rod, which eliminates distortion when striking.
| Parameter | Marking-up kerner | Shock-courner | Automatic corer |
|---|---|---|---|
| Sharpening angle | 90 degrees. | 60 degrees. | Standard (usually 60) |
| The depth of the hole | Minimum | Medium/Deep | Regulated |
| Instrument of impact | Hammer | Hammer | The spring/mechanism |
| precision | Tall. | Medium | Tall. |
If the working end is formed fungus (flattening of metal from frequent hammer strokes), it must be removed on sandpaper or file before sharpening the cone. Leaving the cleaved part is dangerous, since when hit, sharp pieces of metal can break off and injure the eyes or face of the master. Regular inspection and editing of the tool prolong its service life and ensure the quality of work.
Automatic corers: features of use
Automatic corers deserve special attention due to their convenience and the ability to work with one hand. Inside the body of such a tool is a powerful spring and impact mechanism, which is cocked when pressed on the end. When the force reaches a critical value, a sharp descent of the bolt occurs, striking the inner heel of the corer, which creates the necessary impetus for the formation of the hole.
The main advantage spring-model there is no need to swing a hammer, which is especially valuable when working in tight spaces of the car under the hood or inside the cabin. In addition, they allow you to adjust the impact force (in more expensive models), which makes it possible to kirken both soft aluminum and hard steel, without fear of punching through a thin sheet.
Automatic corer device
Inside the cylindrical body there are stingers, a return spring and a trigger mechanism. When pressed on the handle, the buckets move upwards, compressing the spring. At a certain point, the fixator releases the strikers, and under the action of the spring, it moves sharply downwards, striking. Some models allow replacing the working tips.
However, it is worth considering that automatic corers are less reliable when working with very hard steels compared to classic shock models. The mechanism may jam or the spring will weaken over time, requiring maintenance or replacement. However, for most garage and bodywork, they are a great choice, greatly speeding up the markup process.
Safety Techniques and Typical Errors
Working with a kerner, like any other locksmith, requires compliance with safety rules. The main risk is the possibility of bouncing the hammer or chipping off metal particles, so the use of safety glasses is a must. Eye protection. It should always be ensured, regardless of the experience of the master, since an injury to the eye with metal shavings or a fragment can have irreversible consequences.
One common mistake is to use an overly heavy hammer, which results in the formation of too deep holes or even the penetration of thin sheet metal. Also, there is a frequent error of the wrong angle of installation of the tool, when the corer is held not perpendicular to the surface, but with a slope, which shifts the center of the future hole. Deformation of the jock The hammer can also cause injuries and poor quality kernation.
The quality of the drilling determines the accuracy of all subsequent drilling, so saving time at this stage or using a blunt tool is unacceptable.
When working with hardened steels or alloys, special care should be taken, since the risk of slipping the drill and breaking the corer increases. In such cases, it is recommended to use corers from harder alloys or use specialized lubricating and cooling liquids, which also help to remove heat from the contact area.
⚠️ Attention: It is strictly forbidden to hold the part with your hand at the time of impact, if it is not fixed in the vice or strub – this can lead to serious injury to the fingers.
Frequently Asked Questions (FAQ)
Can I use a kerner to work with ceramic tiles or glass?
A conventional steel corer is not designed for ceramics or glass, as it can break the material. For these purposes, there are special hard-alloy corers with diamond spraying or spear-like sting, which do not split, but gently push the material. Using a standard locksmith corer on the tile is highly recommended.
What angle of sharpening to choose for drilling holes under thread?
For the preparation of holes for subsequent thread cutting (drilling under the meter) is also used standard angle of 60 degrees. The main requirement is the accuracy of getting into the center of the marking, since the skewed hole will lead to the fact that the gauge will go crooked, and the thread will be defective.
How is a core different from a corer?
In professional slang, a “kern” is the metal hole itself (deepening) left on the parts, and a “kerner” is the tool that makes that hole. However, in colloquial speech, these concepts are often confused, calling the process itself or the result a tool.
Do I need to lubricate the corer when working?
Lubrication of the corer is usually not required, since the process occurs due to plastic deformation. However, when viscous metals (for example, some grades of aluminum or copper) are kernitted, metal can stick to the tip, which degrades the quality of the point. In such cases, you can periodically wipe the edge with a rag.
How to restore the cleaved end of the kerner?
The open end (fungus) must be polished on an abrasive circle until the cylindrical shape of the tailing is restored. After that, the cone part is sharpened at the desired angle. Leave the fungus can not - when hit by a hammer, the edges can break off and fly away at high speed.