Turning of a conical surface, the generatrix of which has a length exceeding 15 mm, is often accompanied by the appearance of vibrations. This leads to the appearance of waviness on the treated surface. Vibrations increase with increasing length and decreasing diameter of the part.
The surface of the workpiece may become wavy if the cutter overhang is large or if its fixation is unsatisfactory. True, vibration does not occur in all cases (for example, a rigid part with a generatrix of short length and a large slope angle is being processed). In such situations, there is a high probability of tool displacement due to the cutting forces acting on it in the absence of proper support or an excessively large overhang. In both cases, the angle of inclination will be different from the required one.
Due to the short length of the cutting edge, the cutter is quite difficult to install on the machine. Lack of straightness of the tool blade leads to deviations of the hole from the desired shape. It should be noted that the cutter must be installed at the level of the centers of the machine.
Machining holes in the form of cones with an installed tool is feasible if:
- the length of the cone generatrix is a maximum of 15 mm;
- the workpiece is highly rigid;
- the cone to be ground is located close to the fixed part of the product;
- the cone has a large angle of inclination;
- the workpiece is not subject to increased requirements regarding accuracy, straightness and quality of machining of the hole.
To check the slope of a cone made with a cutter, you can use a special template.
Step (conical) drill for metal - types, purpose and characteristics
A cone drill is a cone-shaped drill with one or more longitudinal straight or spiral flutes that form the cutting edge of the tool. Thanks to the variable diameter of the drill, it can be used to produce holes of different sizes in the workpieces.
It should be noted that cone drills come in two main types, which are often confused with each other: directly conical drill and stepped drill.
Conical drills are characterized by a smooth transition of diameter from smaller to larger. With their help, you can drill a hole in metal with a diameter ranging from the minimum to maximum diameter of the tool itself.
Step drills are distinguished by a sequential stepwise transition of diameters. When using this type of cutting tool, it is much easier to control the size of the hole being machined, and its diameter will strictly correspond to one of the diameters of the sequential row of drills.
Scope of use, design
Conical drills have a long service life. This is due to high-strength cutting edges. The stepped tool makes it possible to carry out processing for which it would be necessary to use several ordinary drills. The high price of instruments in this group is mainly due to their versatility.
Twist drills with a conical shank make it possible to process parts at high speed. At the same time, the quality of the edge does not decrease at all. The product consists of the following elements:
- tip for preparatory drilling;
- transition with a bevel to eliminate burrs;
- cutting edge that widens the holes.
With a cone drill it is possible to make holes not only in metal, but also in plasterboard, wood, plastic, and other parts. The pointed end of the tool makes it possible not to use a centering device and can easily enter even dense material. The resulting hole does not need to be further processed using a needle file or grinding device.
The progressive recesses of the device, which are arranged in a spiral, are made in various sizes with a smooth transition. This design increases the efficiency of processing thin-sheet material with a twist drill with a conical shank by approximately fifty percent. Conical tools can be used both manually and when mounted on special equipment.
An abrasive consisting of diamond/titanium particles can be applied to the working area of a two-stage drill. There is no contradiction with the rules of GOST (state standard). This coating makes the cutting edges much stronger. Thanks to this, the conical drill does not need to be sharpened often. Of course, it is necessary to follow operating rules and not subject the tool to excessive loads.
A step drill for metal is often used to correct inaccuracies made when processing a part with another device (for example, torn edges). A product with a conical shank is indispensable if you need to drill holes in thin sheet material or fiberglass parts. The versatility of step devices allows us to say with complete confidence that they will definitely come in handy both in production and in your workshop.
Application area
Conical metal drills are used to make holes in sheet and thin-walled metal. Typically, the thickness of the metal being processed is from 1 to 4 millimeters and depends on the height of the drill step. If the height of the step is 4 millimeters, then the maximum thickness of the sheet or rolled metal that can be processed will be, respectively, 4 millimeters. A step drill allows you to work even with thin sheet metal.
The main difference from other types is that with the help of one drill you can get several standard sizes of holes at once.
Note that there are also conical drills for processing not only metal, but also wood, plastic, drywall, and textolite.
A conical drill (sometimes craftsmen call it a carrot drill) is also distinguished by the fact that when used correctly, the hole has virtually no defects. Proper use of the tool allows you to obtain smooth walls and edges of the hole, the absence of burrs and cracks. After drilling, there is no need for additional hole processing. Therefore, craftsmen often use them to correct defects in holes made with another type of drilling tool.
A high-quality metal cone drill bit has hard, sharp edges, which allows it to work with metal of high density and hardness. Some drills also have an abrasive coating, which further increases their effectiveness. Where another tool is powerless, it is often very convenient to use this type of drill.
The cone drill has a sharp tip, which allows the drilling operation to be carried out without preliminary core punching and additional centering.
Instrument care
Today, the industry produces different types of step drills, which makes it possible to choose devices for certain types of work:
- for processing materials with a high degree of hardness;
- drilling products from various alloys;
- for working with wood, plastic, plywood.
Step Drill Care
Step drills require proper care. After use, the tool must be lubricated with a special compound. If you don't have it, you can use machine oil or liquid soap. Regular lubrication will increase their service life.
Sharpening a tool requires some skills that can be learned by following the recommendations of experts. To sharpen a stepped part, you need to use a diamond stone to restore the guide grooves, which have a straight shape. Spiral grooves need to be sharpened with a sharpening machine. The higher the quality of the drill, the easier it is to restore its parameters. It is better to sharpen a cone tool on a machine using an abrasive wheel with sandpaper.
Choosing a cone drill will provide convenience, ease of use and will give you pleasure with a high-quality result.
Shape and dimensions
All cone drills for metal, as already mentioned, have a cone shape and can have a smooth or stepped diameter transition. The most widespread among mechanics is the step metal drill.
This is due to the fact that it is easier for them to work, since the transition from size to size when drilling is clearly visible, and achieving the desired diameter will not be difficult. The resulting hole has a fairly high surface quality and does not require additional finishing. And a fairly smooth transition from one step to another forms a chamfer for a pre-drilled hole.
Step drills differ in the number of steps, their height, diameter range and pitch. Typically, the diameter of the smallest drill step is 4 millimeters. The maximum size of the hole that a stepped tool can drill is up to 40 millimeters. The standard step height is 4 millimeters. This value determines what thickness of metal the tool can process.
The successive increase in diameter can be 2 or 3 millimeters. The standard step is 2 millimeters. Typically, if a cone drill has a wide range of diameter sizes (for example, from 4 to 40), then the step in this case can be 3 or 4 millimeters.
In specialized stores you can find step drills with a different range of diameters, so they should be selected for a specific set of tasks.
In addition to the working part of the drill, the tool also differs in the shape and size of the shank. The shank can have a cylindrical shape of various diameters, a hexagonal or triangular shape, as well as a specialized profile for specific connectors from hand tool manufacturers. A step drill for metal can be installed on a screwdriver, hammer drill or drilling machine.
Types and sizes of stepped metal drills
Stepped tools used to make holes are classified according to several criteria. In order to select the necessary product, it is recommended that you familiarize yourself with each of its types in more detail. The first factor by which such drills are differentiated is dimensions. Depending on this criterion, the following drills are distinguished:
- small;
- average;
- big.
Step drills also differ in coating material. Today you can purchase cobalt metal drills, as well as titanium analogues. The second type of products has higher strength, which is reflected in their cost.
The diameter of the step drill can vary from 4 to 38 mm
The design of drills of this type assumes the presence of a groove. The most common drills are those that have a straight flute. The second configuration option is to arrange the channel in a spiral. On sale you can find models that have a combined type of groove for chip removal (longitudinal-spiral).
Note! Step drills need to be sharpened from time to time. Sharpening will be more difficult if the tool has a spiral groove.
Of course, one of the most important characteristics of any tool is its size. The steps in such a drill can have different pitches. This indicator may differ depending on the type of product. It is also worth paying attention to another important criterion - the diameter of the metal drill. This parameter varies from 4 to 38 mm. The diameter limit may be lower. It all depends on the number of steps in the instrument. The height of one step is usually 0.5 cm.
Number and shape of working grooves in stepped products
One of the most important indicators of such stepped tools is the number of cutting edges. It is important to understand that this parameter has nothing to do with the drill steps. The cutting parts are located on the grooves of the conical product. In addition to their main function, they perform another one: they remove chips that are formed during the work process.
Grooves in step drills help guide chips while working
Grooves can be of 3 types: straight, spiral, and longitudinal-spiral. Each variety has its own advantages and disadvantages. An example is a straight edge that is easy to sharpen. However, during operation it does not behave as smoothly as a spiral one.
Despite its high cost, the step tool replaces a complete set of metal drills. It is much easier and more convenient to operate one product. The number of grooves is an indicator on which the quality of sheet metal processing depends. The quality of drilling may vary depending on the speed at which the material is processed.
When choosing a drill for making holes in metal material, you need to focus on several points. It is not recommended to purchase the first product you come across, as it may not be suitable for a particular job.
Marking features
Step drills for metal may not always be marked. You should not look for markings on cheap Chinese tools or domestic drills of dubious manufacture. Such manufacturers can sometimes put on drills or their packaging only symbols that they understand, which do not characterize the tool in any way, but serve only for internal classification. But a high-quality professional tool from a trustworthy manufacturer always has a marking.
In the standard case, proper marking should contain in its designation all the main dimensions of the tool, material of manufacture, as well as characteristics of hardness or strength.
Let's take an example of the marking designation ø4-20/2 HSS4241-Co HRC 62.
This cone drill marking should be read as follows:
But most often, instead of marking, the manufacturer indicates on the packaging the main characteristics of a cone drill for metal. Moreover, the description of the characteristics is often accompanied by explanatory images to facilitate consumer understanding.
Price of tapered step drills for metal: review
The cost of cone drills, the design of which involves the presence of steps, is influenced by several main factors. Various materials can be used to make these types of instruments. Titanium drills are more expensive, as they are high-strength and have a longer service life.
The difference in cost is also determined by the diameter of the tool. Products in the shape of a herringbone, which are coated with titanium, can be purchased in a specialized store or placed an order on the Internet. You can buy a 4-20 mm tool for approximately 450 rubles. The price of metal drills with a large number of steps (4-32 mm) can reach 1100-1200 rubles. It is worth noting that this cost is typical for domestic products.
Foreign analogues may have a higher price, which averages 4 thousand rubles. A Bosch tool with a maximum diameter of 39 mm costs approximately 5 thousand rubles. And even this amount is not the limit when it comes to step drills.
Depending on the size, quality and manufacturer, drills can cost from 450 rubles and more
Note! The high cost of such tools requires careful selection. The modern market is replete with a variety of fakes, the quality of which leaves much to be desired. To eliminate the possibility of purchasing a low-quality product, it is recommended to purchase drills only from trusted manufacturers.
The price range for step drills for metal is quite wide. The most correct decision is to purchase a tool that is located in the middle price range. Before you buy this or that drill, you should take into account that the seller must have a certificate for such products.
A step drill is a professional tool that has a long working life and allows you to make holes in metal without the use of auxiliary parts. When choosing such an element, it is necessary to focus on individual criteria, such as the nature of the work and its frequency. It is also worth considering the material of manufacture, diameter, shape of the grooves and the manufacturing company. If you wish, you can always consult with the seller, who will help you choose the right product.
How to choose the right step drill?
To choose the right step drill, you need to decide on the purposes for which the tool will be used. Thus, it is necessary to determine what size holes need to be drilled. The values of the smallest and largest diameters that are planned to be made are especially important.
You should also decide on what hand tool or machine the drill will be used. The type of shank that should be on the drill depends on this. Therefore, you should carefully study the drill chuck connector and clearly know the shape and dimensions of the shank. If the shank does not fit the existing connectors, you will have to separately purchase a special adapter.
It is important to decide on the manufacturer and level of the tool. As already noted, bright golden-colored stepped conical drills are made with cobalt and titanium impurities, with an abrasive coating and have high hardness. They will last longer and allow you to work with thick rolled products, stainless and alloy steels.
Look for the HSS designation on the label or packaging, which means the drill is made of high-speed steel. Try not to buy dubious Chinese-made drills.
Cone drills are expensive, but at the same time quite reliable and durable cutting tools.
But in any case, after some time, their cutting edges become dull, and the tool loses its characteristics. Some step cone drills are designed to be sharpened, and some are not sharpened. Those that are not intended for sharpening are characterized by high quality cutting edges and durability. Source
Recommendations when choosing a product
Cone drills are expensive, so when choosing them, you need to study all the characteristics. According to state standards, high-quality products are made from high-strength alloy steel in the range of the following parameters:
- with diameters from 5 to 80 mm;
- working cone length – from 58 to 85 mm;
- tail diameter - from 6 to 12 mm.
The color of the metal as an indicator of its strength
An important characteristic of a product is the color of the material from which it is made.
The color of a step drill indicates its quality
The gray color of the cone drill with a steel tint indicates that the steel has not been hardened. Consequently, the product is not of high quality and will not last long.
Hot steam treatment makes the steel more durable; products made from such steel have a significant service life and are distinguished by a black color.
Conical products of golden color are made of higher quality metal, in which residual stresses are eliminated. They are more durable and comfortable to use.
Elements of a brighter golden color have high wear resistance. They are coated with titanium or diamond coating, which significantly increases their service life. The long working life explains the high cost of the products.
Which step drills for metal are best to choose?
To make a high-quality hole in metal, you need to select a drill that will cope with this task.
If you need to perform high-precision work in sheet material up to 4 mm thick, then a step drill for metal will be most suitable for this. Such cutting products not only have increased accuracy, but also require the correct approach to the drilling operation.
To process the material correctly, you need to know some of the nuances of selecting and using such a tool. All the intricacies of metal processing using cone drills will be discussed in detail below.
Required Tools
Professional metal drills (for example, Bosch, Makita, Metabo or Hawera) are made exclusively from high-speed steel HSS. Some are coated with a protective layer, which increases their wear resistance when drilling.
Hand tools - drills and drill bits should be selected carefully. If you have no experience in this area, you should seek advice from a store employee. Purchasing an expensive, high-end drill does not always guarantee its long service life.
Compliance with the technology for making holes in metal and a correctly selected drill significantly increases its service life and protects against premature wear. Basic rules for operating cutting tools:
- Selecting the appropriate type of gimlet for drilling metal of a certain hardness. Many manufacturers have developed entire programs using which you can select the appropriate tool.
- Selecting cutting modes, setting the correct rotation speed.
- Correctly selected feed, application of appropriate pressure on the cutting tool.
- Application of cooling. An oil-based emulsion is recommended.
- Proper fastening of the material (for example, in a vice).
- Attaching the drill to the stand is precise and perpendicular.
- Use of an expanded set of gaskets when drilling through holes.
Technological process
Drilling is the process of removing small parts of the material being processed, chips, using a drill. During drilling, the temperature of the workpiece increases. The cutting force leads to damage, the friction force causes a change in the geometry of the cutting edge, plus high temperature, as a result the tool gradually becomes dull.
Most drills are made from high-speed steel with varying cobalt content. It is very important that it is sharpened correctly: the cutting edges are of equal length, the jumper between them is located along the axis of the cutting tool.
This ensures that both edges will perform identical work during the drilling process. The drill will not have runout, the hole diameter will correspond to the size, and heating of the part and the tool will be minimized.
A drill-drill with chamfer correction has a smaller jumper, due to this the cutting edges are lengthened. With such drills you can drill a hole without preliminary marking with a core.
The choice of drills depends on the type of work being performed . NWKa HSS Baildon drills are optimal for drilling:
- structural steel;
- cast iron;
- brass;
- bronze;
- aluminum;
- plastics;
- tree.
Advantages of cone drills
Stepped products have the following positive properties:
A step drill allows you not only to perform high-quality drilling of metals, but also to correct hole defects that were made with other types of products. For example, if the center of the hole is displaced when using spiral analogues, a conical one can completely correct the defect.
It is also possible to expand the holes if necessary to a fixed diameter. Despite the higher cost of cone drills, significant savings can be achieved with frequent use. Due to the absence of the need to purchase a large number of tools of different diameters.
A cone drill allows you to chamfer during drilling and therefore does not require additional time, which saves time during large volumes of work.
Where are cone drills used?
Cone drills are used for drilling holes of different diameters in thin sheet materials. Moreover, the resulting holes are distinguished by such advantages as evenness and accuracy without scoring, chips or burrs. You can drill through thin-sheet material with a regular cylindrical drill, but the quality of the work will suffer and the task will also become more complicated. For example, the slightest deviation of the drill from the surface will result in a triangular or oval hole rather than a round one. In addition, burrs, scuffs and chips are formed, which ultimately negatively affects the quality of the work performed.
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The use of conical drills can significantly simplify the work, eliminating all the disadvantages of cylindrical devices. Due to its advantages, the equipment has found its application in various fields:
- Automotive and repair
- Landscape design
- Construction
- Installation of plumbing equipment
- Installation of electrical installations
The device is not effective in situations where you have to drill holes in materials whose thickness is more than 10 mm.
How to choose a cone drill
An indirect sign of a quality product will be its price. In addition, by the color of the metal it will be possible to tell from the material and what strength the gimlet is made of.
Stepped products can be divided by color into several quality groups:
In addition to the quality of the material, the final cost will be influenced by the diameter of the purchased tool.
Cone drills from domestic manufacturers are always cheaper, but if it is possible to purchase an imported tool, then you should do so. Despite the higher cost of imported products, the resource of manufacturers such as Bosch, AEG, Irwin will be noticeably higher, but only when purchasing original products.
What are the best step drills for metal can be determined by reviews on the Internet. You can get high-quality information on specialized forums where specialists who use cone products in their daily work communicate.
Tool sharpening
To sharpen a cone gimlet, you must perform the following steps:
This way you can restore the functionality of the cone tool yourself.
If you have the opportunity to contact specialists, you can get a complete restoration of the gimlet for little money.
How to drill
With a well-sharpened tool, it is easy to make high-precision holes in a metal sheet up to 4 mm thick.
To perform drilling correctly, it is advisable to follow the recommendations:
If the requirements are met, the cone product will last a long time, without sharpening.
How to sharpen it yourself
Cone drills provide the ability to drill holes with a radius from 0.2 to 1.6 cm. They are manufactured in 2 versions. One of them can be sharpened, the other cannot. The increased price of tools that belong to the second type is due to their high strength.
The cutting edge of such drills (if you follow all operating rules) does not deform for a long time. It is worth noting that an attempt to sharpen such drills for metal will most likely lead to them becoming unsuitable for subsequent use. First, you should study the technology of sharpening a conventional drill, and then take on a similar tool.
To properly sharpen a drilling tool, you need to watch a special video and listen to the advice of professionals. To sharpen a step drill, you do not need a drawing. You can simply restore the original geometry of the drill.
It is possible to sharpen a step drill using a special machine device that is equipped with an abrasive wheel. The working area of the circle should be covered with ordinary sandpaper. In addition, you can use diamond stones of small thickness, which are often used for sharpening knives, scissors, and other objects.
Restoring the geometry of conical tools, the guide recesses of which are located rectilinearly, can be done manually. If they are arranged spirally, it is necessary to use a sharpening machine device. Remember that the better the quality of the drilling tool, the easier it is to sharpen it.
Manufacturers of step drills
Products made in China are of low quality (there are exceptions). To buy a good cone drill, you should pay attention to tools made in Europe and Russia.
1. “Zubr” - stepped drills from a domestic manufacturer are of reasonable cost. The quality is at a fairly high level.
Cone drills can be made from ordinary tool steel or coated with more wear-resistant alloys. In the latter case, the price will be significantly higher, but the quality of the cutting surface will remain sharp longer even when performing a large volume of work.
2. “Attack” - Russian-made conical drills, which in quality and cost are not inferior to the best products from foreign companies.
Reviews about the products of this company are only positive, so you don’t have to worry about the quality, and in order not to overpay, you should select a tool taking into account the maximum diameter that will be needed in the work.
3. “Bosch” - the products of this German company are excellent for professionals and for working with metal at home.
The diameters on the tool are marked using a laser system, so in case of long-term use, the inscriptions are not erased. To increase the drilling speed, the top of the Bosch step drill is sharpened crosswise, and the workpiece is ground in both the transverse and radial directions.
Such processing of the tool allows, when using it, to obtain a high-quality hole, the diameter of which will fully correspond to the stage of the product.
4. “Falon-Tech” - drills from a German company have an additional titanium coating, which allows you to increase the tool life by more than 2 times.
The product has a laser marked diameter and a standard shank that is ideal for use with a screwdriver or hand drill.
Despite the increased quality of the product, its cost remains low. If you need to purchase a cone drill for home use, then the choice of products from this company is the most optimal.
All of these cutting tools do an excellent job of drilling metal up to 4 mm thick. If you need to work with thicker metal, it is recommended to use core drills.
Conclusion
We figured out what a cone drill is needed for. A properly selected product will last for many years. When working with metal of small thickness, to obtain high-quality holes, the use of drills of this design is the optimal solution.
Source
Color of step drills used for metal processing
All step tools used for processing metal sheets of small thickness are divided into groups according to quality. Identifying a particular drill is quite simple. All you need to do is pay attention to its color. The following instrument options are currently available for sale:
Step drills come in black, gray, dark and bright gold
- gray;
- black;
- golden (dark);
- golden (bright).
Gray drills. This color indicates that the material for the manufacture of the product is ordinary steel, which has not undergone additional processing. These tools do not have high strength characteristics. One of the advantages of such devices is their low cost.
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Black. This color indicates that the steel product has undergone additional treatment with steam heated to high temperatures. This enhances the technical characteristics of the tool and extends its service life. The price for such products is higher than for gray ones.
Note! The material and the product itself made from it must comply with all the parameters specified in GOST. Gray metal drills are not suitable for long-term use.
Black drills are treated with high temperature steam, which increases the technical performance of the tool
Golden (dark). Such instruments undergo quite intensive temperature treatment. This type of procedure helps eliminate stress in the metal product. The result is a durable part that is best suited for extended use. The cost of such drills is quite high.
The color of the drill is not related to its configuration. All products have a special channel. The presence of a groove allows for efficient drilling of metal. Special curved channels can also be found in other products that are used for drilling metal. A good example in this case are metal screws with a drill.
Golden (bright). Another option for step type drills. This coloring is obtained by applying a special protective coating of titanium to the surface of the product. Such tools have the highest strength.
Cone drills
The shape of the working part of such drills is a conical series of step-by-step annular transitions and a longitudinal-spiral or simply longitudinal groove, forming sharp cutting edges.
This makes it possible to use one tool to produce holes of different diameters. Thus, we save not only time on replacing drills during work, but also money on their assortment. Progressive changes in size are made with smooth transitions between steps. This surface shape promotes easy rotation and increased processing efficiency of sheet materials. The use of high-strength steels for the manufacture of cutting edges on step drills provides them with longer service life without sharpening.
An example of a cone drill
The tool allows you to perform technological operations at a time, which under normal conditions require the sequential use of several tools. The material can be processed at high speed, guaranteeing excellent edge quality, even with the smallest sheet thickness. This form of arrangement of cutting edges makes it possible to drill not only sheet steel, but also soft non-ferrous alloys, wood, plastics, gypsum and other products.
The sharp tip eliminates the need for pre-punching and ensures precise positioning of the tool during operation. Step drills can be installed on stationary machines, portable hand drills, and with adapters, even on a hammer drill and grinder.
Conclusion . Considering the design features and technical capabilities of drills, we can say that the main purpose of this tool is to drill holes in thin sheet workpieces. In addition, they are used to correct defects formed after the use of traditional drills in the form of burrs, misalignment, triangular holes and others. Therefore, such drills are widely used in car repair, plumbing installation, electrical panel manufacturing, construction and finishing work.
Sharpening cone and step drills
Sharpening on professional equipment
During operation, the cutting edges of the tool gradually become dull and require sharpening. The most correct decision in this case is to contact a specialized workshop that has the equipment and specialist to perform such work. By paying a certain amount, you can be sure that the drill will be returned to you in working condition and you will not have to decide on purchasing a new one. This sharpening guarantees:
- maintaining the diameter of all stages,
- maintaining the correct cutting edge angle,
- no overheating.
Sharpening by hand
However, it is not always possible to find craftsmen who will undertake sharpening of a conical step drill. Most workshops refuse, citing the complexity of execution and insufficient experience of workers.
Therefore, quite often you have to sharpen the drill yourself. In this case, the following basic rules must be observed:
- the cutting edges of each step must remain identical with precise dimensions;
- the angle of the edge planes remains unchanged as a result of sharpening;
- the distance between the cutting angle and the opposite side surface on each diameter must be the same;
- sharpening is carried out in the presence of a support stand or with rigid fixation of the drill;
- Only fine-grained abrasives are used for work;
- when performing, one should focus on the maximum possible restoration of the original geometric shapes of the cutting edges.
Good results can be obtained if you use a sharpening machine with an abrasive wheel, the surface of which is covered with sandpaper. The quality of the sharpening performed is determined by the type of chips formed during drilling. With a high-quality result, it will be the same shape and size.
If the grooves have a rectilinear shape, sharpening can be done manually using an even rectangular block, processing several edges at the same time.
If the machine is replaced with a grinder, it must be well fixed in a stationary position and sharpening must be carried out with a strong support bar to hold the drill.
And yet, if you have the opportunity to entrust sharpening to specialists, take advantage of it. Lack of practical skills can lead to damage to an expensive tool and unexpected material costs.
Types of Step Drills Available for Sale
For the manufacture of cone tools, high-speed steel HSS (High Speed Steel) is used. The types of additional processing of the material and surface can be judged by the color of the metal :
A thin layer of abrasive material made from artificial diamonds or titanium alloys can be applied to the surface of the drill. Such processing does not contradict the requirements of the standards and significantly increases wear resistance.
Step drill in action, video
Existing shapes and sizes
There are three forms of cones : a regular stepped one, in the form of a truncated figure without a guide point, and a figure made up of two conical parts with different angles of inclination of the surface.
Shanks for mounting in the chuck can be cylindrical, triangular or hexagonal. The last two types eliminate rotation, but create the risk of injury when the drill jams in the material being processed. However, with sheet thickness up to 4 mm this usually does not happen.
When choosing a tool, you need to pay attention to the size of the starting and finishing diameters. The first size starts from 4 mm or 7/8”, the latter maximum can reach 38 mm. The successive step steps up to 12 mm are every 1 mm, and after that every 2 mm. The usual step height is 5 mm, but can be found at 3, 4 and 6 mm. The value of this size determines the maximum permissible thickness of the material intended for processing.
Number and shape of working grooves
The number of cutting edges is determined by the number of grooves (not to be confused with steps), which can be from one to three. The shape of the grooves is longitudinal straight or spiral. Experts say that the spiral shape increases the service life of the tool, but makes the sharpening process very difficult. Step drills with three flutes are designed to work at high speeds, and with one recess the processing speed must be reduced.
The quality of metal processing at low speeds also depends on the number of grooves.
Stepper drill markings
A high-quality branded tool is always marked with an alphanumeric designation, which indicates:
For example, the inscription Ǿ 4-24/2 HSS-Co 72 says that the first diameter is 4 mm, the last 24 mm, the sequential step of sizes is 2 mm (4, 6, 8 ... 20, 22, 24 mm), made of high-speed steel with the addition of cobalt, Rockwell hardness 56 mm.
In addition, the marking may additionally contain data on the accuracy class and the manufacturer's trademark.
Pros and cons of using step drills
| Advantages | Flaws |
| replacing several drills with one universal drill with different diameters | high price |
| high quality drilled holes | complex sharpening technology |
| possibility of processing thin sheet materials | a cone drill has a conditional accuracy of hole diameter |
| drilling at high drive speeds | |
| reliability and durability | |
| short length, creating more comfortable working conditions | |
| savings on purchasing a complete set of drills |
The most famous manufacturers and prices
A brand very often speaks not only about the quality of products, but also seriously affects their cost. Well-known Western manufacturers guarantee the reliability of their products, but the price of their drills is much higher than domestically produced tools.
Cheap doesn't mean bad ! Among the popular Russian brands producing high-quality stepped cones, the trademarks “Ataka” (ATAKA) and “ZUBR” should be noted. Among the Ukrainian products, Globus conical drills are in demand. The manufacturing level of this instrument is not much different from its European counterparts, but the price can be 2-3 times lower.
The most famous European manufacturers of cone drilling tools are the following brands:
*I would like to point out that the figures may have changed since the publication of the article, so they are given for comparison purposes only.
For a more complete review of popular manufacturers, see here .
The same should be called the American brand MILWAUKEE and the Japanese Yato. You can hear only good reviews about their products, and if not for the high cost, then drills from these brands can be universally recommended for wide use.
Chinese products are distinguished by high manufacturing precision, but the quality of metals leaves much to be desired. Tools from the Middle Kingdom are most often short-lived, quickly dull and wear out; you can find a full range of tools on the most popular website for such products, aliexpress.
Video review of a tool purchased on this site
How to make the right choice
The purchase of a step drill should be based on an accurate formulation of the technological problems that must be solved when using it. Therefore, when choosing, take into account :
As already mentioned, the brand also determines the quality, but in this matter you need to independently choose the best option for the ratio of price and reliability of the tool. See a review of popular manufacturers here .
When purchasing tapered step drills, you will be drawn to a very wide range of prices. For example, products made in Russia and Ukraine with a final diameter of up to 20 mm cost an average of 400-500 rubles per piece, and with a final size of 30 mm or more they are sold 2-2.5 times more expensive.
Tools from well-known foreign brands up to 20 mm are sold for no less than 3,000 rubles, and with a finishing diameter of 30 mm for 5,000-7,000 rubles. Therefore, many buyers prefer to buy two or three drills from a domestic manufacturer rather than pay for one foreign product.
Drilling metal
A special feature of the drills is the presence of a sharp edge, which allows for mechanical processing of the material. They have an equal diameter along the entire length, and the blade is sharpened at an angle of 118°. The sharpening angle varies depending on the hardness of the material, for example, for alloy steel, it is 135°. This type of drill is made of HSS steel with 5% cobalt. During operation, they require cooling with special drilling oil .
In order to drill a nozzle in metal evenly and accurately, it is necessary to use a guide device - a jig.
When drilling, it is best to use as little force as possible. When drilling a through hole, when the moment of exit of the cutting tool approaches, it is necessary to reduce the feed so that the part does not tear out, the drill does not break, or burrs do not form.
A conical drill is used to produce a conical hole in metal. It is used as an independent tool. They can drill a cylindrical hole, turning it into a conical one. A conical hole in the metal is made on a lathe in order to drill and bore the resulting nozzle with a cutter.
Cutting modes
The most common mistake is using too high a drilling speed . The more difficult the material to process, the lower the drilling speed should be used. For example, in the case of drilling an 8 mm hole in brass, the drilling speed should be 2500 rpm, for harder alloy steel - 800 rpm. The best sign that the drilling speed is correct is nice, long chips.
Depending on which tool to choose, cutting parameters are important. It is necessary to select the correct rotation speed and feed. Bench-top drilling machines provide the best parameters, but they cannot be used everywhere. It is necessary to follow the principle: the lower the speed and the lower the feed, the longer the tool will last.
For example, take stainless steel, 8mm hole, 4mm thickness, cooling lotion or oil, HSS drill bit, drill or drilling machine: The revolutions should not exceed 400 rpm, and the feed should not be more than 0.10 mm/ turnover In other words, you can drill at a speed no higher than 400 rpm. But this speed is not optimal. Therefore, it would be optimal, for example: 170 rpm, and the feed for every 30 revolutions is 1 mm (three times less than recommended).
Cooling the drill during the drilling process is very important. Use emulsions, oils, drilling sprays. Water should be avoided, as it does not have the properties of lubricating fluids, but only cools.
Large diameter holes
To the question of how to drill a large diameter hole in metal, there is only one answer: in the technological process of drilling necks . For example, you need to increase the neck and get a size of thirty millimeters in diameter. First, it is drilled with a tool of a smaller diameter, for example, four millimeters, then to a size of 8 millimeters, then 12 millimeters, and so each size is expanded to the result.
A large diameter neck in a product can be made on a lathe. The operation is as follows: drilling a hole, boring the neck of the desired size. As pre-drilling is required, the process can be divided into stages: small-diameter drilling, reaming with a gradual increase in drill diameter.
Drilling thin sheet metal
The peculiarity of obtaining an armhole in a thin sheet of metal is its reliable fastening . After the drill comes out to the other side, there is a danger that the sheet may suddenly jam and tear out if it was held in your hands. The best way to securely fasten a sheet is a clamp. In this case, the risk that the tin will be torn out is much less. The number of burrs formed is reduced, which will greatly facilitate the finishing of the element.
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If the metal is 0.1 millimeter thick, you can make a hole without a drill by using a metal punching tool. Its design is very simple, like pliers. A punch is attached to one lever, and a matrix to the other. The principle is the same as cold stitching using a stamp.
To cut a through groove in sheet steel, you need to drill a successive row of holes according to size, connecting them into a single slot using a chisel and hammer. To do this, it is necessary to cut off the bridges between the holes and smooth out the unevenness with a file.
Metal pipes
When drilling a metal pipe, make sure that the workpiece is securely secured in the vise. It is advisable to mount the drill on a vertical stand. Insert a piece of wood of the same shape and size inside the pipe, which will protect the pipe from deformation. In this case, use low feed.
Getting narrow nozzles
Drilling deep holes of small diameter can only be done on a special machine or lathe using a device. The part is clamped into a 3-jaw chuck and checked for runout with an indicator. The device is mounted on a tool holder. A drill chuck with a drill is installed in the fixture. First, the hole is centered, then the nozzle is drilled to a given depth. Using a tailstock is problematic, since it needs to be constantly removed to remove chips and lubricant.
To obtain vertical holes, a right angle drilling device is used. For an electric drill, this is a vertical stand at an angle of 90 degrees to the base. The easiest way is to use a vertical drilling machine.
The working area of a cone drill (also known as a “step drill”) is a spiral-shaped recess with several annular transitions of different radii. This device, due to such design features, makes it possible to determine at any stage of processing what size the hole is.
At first it seems that the use of conical step drills, which are characterized by an increased price, is inappropriate, since it is always possible to take a drilling tool of a specific radius and use it to make the desired hole. However, they have some advantages that make their use worthwhile in a variety of situations.
What kind of work can you use herringbone drills for?
Functional parts of this type are used to create holes in metal sheets. Such drills belong to the category of specialized tools, so their cost is quite high. Often this fact stops buyers from making a purchase. However, the purchase of such a product may be justified, for example, in cases where precision is required when performing work.
Step drills are mainly used to create holes in metal.
Each level of the step tool has a unique diameter that increases as it approaches the base. The convenience of this type of design is undeniable, since it is very easy to select the desired diameter during drilling.
Such products are used to make holes in metal. Herringbone drills for metal are distinguished by high quality drilling. Moreover, this is noticeable even when very thin sheet material is processed. Other drills do not allow making a smooth hole in a metal sheet up to 1 mm thick.
It is worth saying that step-type tools are used not only for metal processing. They can also be used for drilling holes in the following materials:
Herringbone drills can produce perfectly straight holes
If you need to make a hole in a pipe, it is also recommended to use a metal step drill. Reviews about such a tool can be studied on the Internet. It should be said that step drills are often used to grind the edges of holes made with other tools. Metal shavings can also be removed manually, but this is much more difficult.
Design and characteristics of a cone-step drill
These instruments have a rather complex design. Their configuration may differ depending on the variety. Let us consider in more detail what parts such products consist of. The top of the drill is represented by a pointed tip, which makes it possible to cut into metal of any density without much difficulty.
Other tools are also used for processing metal sheets, for example, crown tools. A metal drill of this type does not require the use of auxiliary centering devices, but it is not suitable for working with thin metal. Spiral analogues also do not allow such work to be performed accurately.
Step products are very effective when working with aluminum, steel, copper and other sheets and pipes. Tools of this type are shaped like a cone, which includes 2 grooves. They promote drilling of materials. During operation, when moving to the next level, a chamfer is formed for the hole that is created by the previous step.
Due to their design, step drills are suitable for working with copper, steel and aluminum sheets
A 4-32 mm step drill for metal also has an opposite end, which is mounted in the tool chuck. The opposite end, or tail, has the most suitable design for this and consists of six edges. The advantages of such tools are undeniable, which is why many craftsmen recommend them for working with metal parts.
