Carbide drills for metal
High efficiency in processing products from such materials, like cast iron, non-ferrous metals, plastic, artificial and natural stone, brick and concrete, demonstrate carbide drills. That's why they got this name, that on their cutting part special plates from firm alloys are soldered. The use of these drills allows, example, almost double the productivity of cast iron compared to drilling, performed with a tool made of high-speed steel.
Carbide drills for cutting holes in rails
Though, that cutting plate, which is equipped with such a drill, differ in exceptionally high hardness and wear resistance, it is used infrequently for the processing of steel products, as for this purpose it is necessary to provide high rigidity of working elements of the used equipment. If compliance with this requirement is not ensured, the tool vibrates, which will lead to chipping and even breaking of hard-alloy plates.
Selection criteria
Choosing carbide drills, which may have different geometric parameters and design, the following characteristics should be considered: product material, in which it is necessary to drill a hole, as well as the diameter and depth of the latter. The most important parameters, to which it is necessary to pay attention, choosing a drill with carbide inserts, is:
- material, from which the cutting part is made;
- the strength of the hard alloy used;
- drill quality;
- trademark, producing country;
- cost.
Drills with carbide inserts for drills have sharp cutting edges
Though, that carbide drills, released under well-known brands, differing in the highest price on the market, it is desirable to choose them, as their quality and reliability are at the highest level. Given that fact, that any carbide drill is not cheap, it makes no sense to choose a tool of dubious quality from unknown manufacturers.
Types of drills with carbide inserts
A large variety of carbide drills is available on the modern market, designed to perform work on metal and other materials. The classification of such a tool is based on several parameters, to which, in particular, include:
- carbide plate material, as which alloys of brands VK6 can be used, VK8 and others;
- method of attaching carbide inserts to the main part of the drill;
- form, which have carbide inserts;
- the shape of the grooves between the working surfaces of the drill, designed for efficient disposal of treatment waste.
As a material for making cutting inserts, which is equipped with a carbide drill, mainly tungsten-carbide alloys are used. The most popular is the alloy brand VK8.
Properties and applications of tungsten alloys
Such alloys, obtained mainly by powder metallurgy, fully meet its name - "solid". In particular, hardness of the popular alloy brand VK8 depending on the conditions of its production, is in the interval 1670-2800 units on the Rockwell scale. Thanks to this drill, equipped with cutting plates made of VK8 alloy, can be successfully used to make holes in such materials, as alloy steels (including heat-resistant group), cast iron, solid wood. That is also important, that the alloy of the VK8 brand in comparison with other hard-alloy materials differs in reasonable cost.
Carbide inserts can be fixed on the cutting part of the drill by soldering or by screw (mechanical) connection. In the first case, carbide plates can be reground a limited number of times, although characterized by higher reliability. in addition, they break quite often. That is why the tool has gained great popularity, non-transferable cutting plates on which are fastened mechanically.
Types of carbide plates, used for drills
Carbide-shaped plates are used to equip drills of this type:
- parallelogram;
- rectangle;
- rhombus;
- wrong triangle (such plates are characterized by the presence of six cutting edges).
Of great importance when using carbide drills for metal and other materials is the shape of the grooves between the working surfaces of the tool. Regardless of the shape of such grooves, their inner surface must be carefully polished, that will provide effective removal of shavings from a processing zone.
Carbide drill with internal coolant supply
Features of tool design
Drills with carbide inserts are characterized by a number of design features. Here are the most important.
- Reduced to 20-35% the working length of the drill is explained by that, that its regrinding is performed only on the carbide plate. Length of drills of this type, if they are used in conjunction with a conductor, may be the same, as in the high-speed tool.
- Increasing the diameter of the drill core towards the shank is performed in the range of 1.4-1.8 mm for each 100 mm in length, as in the heaviest instruments of other categories.
- The value of the angle of the helical groove of the tool depends on that, how deep the hole needs to be made.
- On the transverse edge of the drill it is necessary to make a sub-point with dimensions of 1.8-3.5 mm, which allows to reduce axial forces and reduce the load on the body of the tool.
- Conical shank, by means of which the drill is fixed in the machine spindle, must be precisely fitted to the landing part, which will increase the rigidity of the drill bit and minimize the risk of vibration loads, which can cause chipping of the carbide plate and even its breakage.
- To increase the reliability of the use of carbide drills for metal, in their inner part often make a hole for the supply of lubricating and cooling fluid. This reduces the cutting temperature, reduce the intensity of tool wear, as well as to facilitate the process of removing chips from the processing area.
Drill device with replaceable plates
To give the working part of the drill the necessary hardness (56-62 units on the HRC scale), the tool is subjected to heat treatment, which, usually, performed simultaneously with the soldering of carbide plates.
High processing productivity, as well as the stability of drills of this category provides a number of parameters. These include the shape of the carbide plate, geometric parameters of its front surface, as well as material, from which such a plate is made. Currently, the most common tools with carbide inserts of the correct three - and quadrilateral configuration, which allow you to drill holes with almost flat bottom.
Better drilling results can be achieved, if you use the tool, equipped with profiled carbide inserts.
Drills with such plates, the cutting part of which is made in the form of a wave, allows to carry out processing by technology of step-by-step cutting. The use of the latter not only provides stabilization of the position of the tool at the time of its cutting into the workpiece, but also minimizes the risk of its removal in the process of further processing. in addition, drill with a wavy cutting edge can significantly reduce the cutting force, formed during drilling.
Drills with mechanical fastening of replaceable polyhedral plates (drills with MNP)
Design of drills, equipped with replaceable carbide inserts, allows to carry out with their help not only drilling, but also such technological operations, as boring pre-drilled holes, chamfering. In such cases, the peripheral carbide plate is involved, attached to the tool.
Drills with hard plates, which are fixed to the tool mechanically, are effectively used for processing of inclined and concave surfaces, while processing with such a tool can be performed without pre-drilling holes. To successfully cope with such a technological task, the amount of feed, with which the tool cuts into the workpiece, must be reduced by 50-70%.
Cooling and lubrication of carbide drills
As mentioned above, to make drilling with carbide inserts more efficient, it is necessary to provide internal cooling of the tool. It is possible not to use lubricating and cooling liquid at application of such drills, when the depth of the molded hole does not exceed one diameter of the tool.
On the quality of the hole, as well as the speed of its drilling is affected not only by the amount fed into the inner cavity of the drill ZOR (no less 12-15 l / min), but also the magnitude of the pressure (no less 12-15 Atm). Lubricating and cooling fluid, supplied to the processing area in such quantities and with such pressure, which provides not only intensive cooling of the tool, but also efficient removal of chips and other drilling waste.
Drilling with external coolant supply
Useful recommendations
Before making a hole in a metal product, using including carbide drill, the tool should be centered. You can use such a convenient device, as a centering pin. The place on the surface of the product, on which the center of the future hole will be located, should be pre-nakernit.
An important parameter when using drills with hard-alloy platinum is speed, with which processing is performed. When using such a tool, the speed of rotation of the machine spindle must not be lower 25% from the recommended parameter. It is very important not to underestimate or exceed (more than on 20%) recommended drill speed, as this may cause the tool to vibrate, chipping and even breaking of carbide plates, which it is equipped with.
Modes of cutting with drills with SMD
This is the drilling parameter, as the supply of a cutting tool, is also important. At the initial stage of drilling, the drill must be fed at speed, which is twice lower than recommended, and as you cut into the material being processed, this parameter can be gradually increased. This should be borne in mind: if the drilling is performed with a blunt tool or the workpiece is too hard, increase the feed rate will not work, no matter how much pressure you put on the drill.
And finally a little video about it, how to drill hot metal with carbide drills.
