There are several ways to make holes in the metal. In industry, they break through on hydraulic presses and dies, and can be squeezed out (for this, steel must be heated above the recrystallization temperature in order to eliminate the hardening effect and correct the fibrous structure). Holes are cut on a laser cutting machine, on an EDM machine and many other technological methods. However, drilling is the most common method for cutting holes in steel and metal alloys. At home, you can hardly find any alternative to a drill for metal.
Features of the tool for drilling holes
A metal drill has characteristic external features, due to which it cannot be confused with a tool designed for processing other materials (concrete, wood).
This drill is double-entry, has two spirals. Sharpening a drill for metal occurs on an abrasive (preferably diamond) wheel as wear and fatigue sparking of the working part. The special heat treatment (hardening plus low annealing) of the drill makes it quite elastic, it does not burst during impacts and distortions, which are inevitable when working with a hand drill.
The purpose of the spiral grooves is the removal of chips from the cutting zone. According to them, in industrial production, when machining on machines, a lubricating coolant is supplied to the hot cutting edge . Also, the grooves improve the cleanliness of the inner cylindrical surface of the hole.
However, there are also drills with one spiral groove. They are designed to perform very specific tasks: for example, for cutting barrels of firearms.
Tool Recommendations
When working with drills of a specific diameter or if you have a whole set of drills for metal, use a tool from well-known manufacturers. Yes, it will come out a bit more expensive, but it will last a long time, unlike numerous fakes, which quickly break and go dull, since the production of cheap tools is performed in violation of the technological process.
Another reasonably significant reason why you should buy a branded instrument is a guarantee from the manufacturer. If the drill was operated strictly for its intended purpose and in accordance with the established standards, but there were problems with it, then the manufacturer undertakes to reimburse the money spent on the purchase of the drill (as well as any other tool).
Drills of domestic production are marked in accordance with state standard No. 19265-72 "High-speed tool steel for the manufacture of drills for metal." Marking is applied to the cylindrical shank of the drill.
If you can buy an old instrument from the time of the USSR, be sure to use it. The Soviet instrument is very reliable; it was once valued all over the world. The instrumental industry of the state supplied high-quality products to many countries around the world.
What can the color of the drill tell?
In appearance , a professional can tell a lot about the stages of its manufacturing technology. Drills are often further hardened by applying wear-resistant coatings, diffusion saturation with atoms of other chemical elements (nitriding or boronation is mainly used).
Matte gray have drill bits for metal, which were not subjected to additional hardening treatment, except for hardening and tempering. Such a tool also serves well and is an ideal option for the home, since at home they do not use a drill very often, so there is no point in overpaying for the reinforcing layer.
The titanium nitride- based coating has a golden color . The coating is wear-resistant, anti-friction, that is, the tool heats up so much, and therefore does not allow red brittleness to occur (lowering the operational properties and strength of the metal when it is heated) and does not cause a decrease in the elastic modulus.
The design and geometry of a simple drill
The word “simple” in this situation, perhaps, is not entirely appropriate, since the technological process of manufacturing the tool is quite complex and requires high qualification from the performers. So in professional slang they call the most common type of drill for metal - a solid tool made of high speed steel, or an ordinary spiral drill of a cylindrical shape. Sometimes such drills are additionally hardened by chemical-thermal treatment methods. At the same time, they strive to obtain a small diffusion layer of the saturating element (nitriding).
These drills can be re-rolled a large number of times. And this, of course, is their significant plus. Cutting edges form a cone with an angle at apex of 118 °. The deviation in the angular size is not more than 30 about . Even a drill that breaks can be sharpened in a new way. At the same time, its outreach and, accordingly, the depth of drilling will change.
Distinctive features of conical drills
This type of tool is intended for machining on machine tools of machine-building plants. The shank is made in the form of a morse cone. Its parameters are strictly unified. A metal taper drill is installed in the mandrel. To remove the drill (for example, to give it to the tool room), you need to insert a wedge of sheet metal into the opening in the mandrel and hit it with a hammer.
It should be said that earlier drills were made, the cartridge of which was designed for the taper shank of the drill. The spindle speed of such devices is relatively low, and besides, they are low-power.
HSS metal core drill
This type of drill is an exception to the rule and is completely unlike its counterparts. Outwardly, it looks more like a concrete drill, but it is not. HSS type drills are designed for drilling large diameters. It should be remembered that with this tool you can make a through hole only in a relatively thin sheet metal.
Carbide drill
Hard alloy is a special type of material obtained by special high-tech methods of sintering nanoparticles of various elements under high pressure. It is characterized by much greater wear resistance and endurance compared to traditional tool high-speed steel. However, a tool made of such a material is much more expensive, therefore, this type of drill is advisable to use for processing only particularly strong structural alloyed materials with high cutting speeds. It is mainly used in processing at machining centers with numerical program control (CNC).
As a rule, the drill is not entirely made of carbide material. The most common are drills with interchangeable blades. And this solution is very successful: after wear of the cutting part of the insert, it is enough to simply unscrew and rotate the other side. This saves the worker from numerous adjustments and setting relative coordinates in the CNC system and running around in the tool room of the workshop.
Description and features of a step drill
Such drills appeared on the market relatively recently and immediately gained popularity in home workshops and households. With such a drill, there is no need to store an uncomfortable case with a set of tools of various diameters in the house. A single step drill for metal allows you to get holes in the sheet material from 6 to 30 mm. But still such a drill can penetrate only thin sheet material. Unfortunately, deep and blind holes cannot be obtained with it.
The purpose of the left-handed drill
The industry produces drills with a left spiral. They are quite rare to meet, but still they are. Basically, they are used by machine tools to drill a broken tool (drill, taps, alignments, etc.). Such a drill is simply indispensable if a broken tool is stuck in an expensive workpiece, and there is no EDM machine available.
Combined screws
On the slang of turners, self-tapping screws, at the end of which there is a drill, are called bugs. The thread is removed into the head of such a screw. The thread pitch is very small, which allows you to securely fasten thin metal products together. For the manufacture of metal screws with a drill, ordinary structural steel is not suitable. High-strength alloyed grades of materials are used.
A self-tapping drill for metal can easily penetrate sheet material up to 2 mm thick, no more, otherwise the drill will burn.
Sharpening a drill at home
The drill is sharpened when it is hooked and begins to enter the metal tightly when cutting, while it is warming, an unpleasant smell is felt in the air. You may need to regrind the tool that was in the hands of an inexperienced master. And finally, the drill may break during operation. In this case, it is not thrown away, but sharpened and reused if the length meets the requirements.
To ensure symmetry and correct geometry, it is better, of course, to sharpen drills on special machines. But not every farm has such equipment. Even on an ordinary emery, you can sharpen a drill bit for metal. How to do it qualitatively? You must first fill your hand. After several unsuccessful trials, everything will start to work out for you.
The main thing in the process is to correctly designate and adhere to the axis of the tool so that the cutting edges are the same length. Without this, the drill will “drive” during operation, crumble intensively and eventually break.
The surfaces of the cutting edges are alternately sharpened on the emery, while a characteristic jumper is formed between the cutting edges, which first touches the metal when it is inserted. In the course of work, both hands are involved. While the left hand fixes and holds the tool, the right gives it a rotational movement.
Working on an emery is fraught with health risks: the workpiece can be pulled out, a small piece can be chipped, which, by bouncing, can damage the eyeball, the tool can fly off the emery wheel and damage its hands. Therefore, with these types of work you need to be vigilant and comply with safety standards and rules when working on industrial equipment.