Tools required for work
On an industrial scale, special machines are used for drilling metal parts. In everyday life, a drill is used, both manual and electric. Moreover, the first is irrevocably a thing of the past, since such a tool is already inconvenient and unproductive.
Many home workshops are equipped with compact drilling machines. They differ from industrial designs not only in size, but also in performance. And the most practical option for the home is a special device in which an electric drill is attached.
Previously, such a stand could only be seen among folk craftsmen. Now it is sold in any hardware store. The convenience of the device is that it has a vice. The part is fixed motionless, and the cutting tool, clamped in the drill chuck, is fed to it strictly vertically.
They make holes in the metal using special drills. And most often they are called drills. They have a cutting part, a shank and a working surface that removes chips from the hole. Cutting tools differ from each other primarily in diameter, length and shape.
Metal drills Source skladom.ru
Types of drills for metal:
- Spiral, as a rule, have a cylindrical shape. Their diameter can reach up to 80 mm, and the cutting edge is sharpened at an angle of 118 degrees.
- Conical ones are made in the form of a cone with a stepped surface. In addition to drilling holes, they are good at correcting defective passes that have already been made.
- Crowns are often called annular cutters. A hollow serrated drill can make a neat hole in the thinnest metal. The cavity in the bit also helps with deep drilling by allowing chips to pass through.
- The feather ones have replaceable working plates. With their help you can get the perfect hole by penetrating to great depth. Moreover, in metals of any strength.
Good drills are made either from cobalt or high-strength alloys. Typically, tool steel is selected for the base, and the cutting edge is either alloyed with cobalt, or carbide alloy plates are fixed to it. Cobalt drills are not afraid of high temperatures and can drill metal with the highest viscosity. Carbide tools are capable of self-sharpening during operation.
Drill with cobalt coating Source zakaz64.ru
Some difficulties of the process
As the depth increases, more difficulties arise with processing the excavation.
When deep drilling, a specialized tool is used, technically equipped with additional capabilities for the use of cutting and other types of devices. This is necessary for the reason that the use of standard devices does not allow achieving high productivity of the process, and sometimes makes it impossible.
Solving technological problems often requires the participation of non-standard devices, which can be equipped with special equipment.
Drilling mode
To drill metal correctly, you need to select the desired rotation speed of the drill. The force applied to the drill also plays an important role. It is guided along its axis and ensures the depth of the cutting tool with each revolution. The correctly selected mode is easily determined by the chips. If the effort and speed are not exceeded, then it is long and beautiful.
There are simple rules for correctly selecting a drilling mode. The harder the metal that needs to be processed, the lower the number of revolutions the drill should have. This principle also works when selecting the diameter of the drill. The thicker the drill, the lower the cutting speed.
Dependence of drill rotation speed on its diameter:
- 5 mm – from 1200 to 1500 rpm;
- 10 mm – 700 rpm;
- 15 mm – no more than 400 rpm.
You also need to monitor the force applied to the drill. The deeper the immersion into the metal, the less pressure on the tool is necessary. Ideally, the pressure on the drill should gradually decrease during the drilling process.
Adjusting the speed of a drill Source ytimg.com
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How to drill in hardened steel? — Machine tools, welding, metalworking
To improve the basic characteristics of the metal, it is often hardened. This technology involves increasing the hardness of the product due to strong heating of the metal and its rapid cooling.
In some cases, after heat treatment it is necessary to perform drilling. By increasing this characteristic, drilling hardened metal becomes more difficult.
Let's take a closer look at all the features of drilling hardened steel.
How to make the right hole
To drill a hole in metal, you first need to securely secure the workpiece. If the part has good mass, it is often enough to simply place it on a flat surface. Its own weight will not allow it to “slither” from side to side.
Parts of small dimensions and light mass must be clamped in a vice. If you first mark the future center of the hole according to the applied markings, then this notch will allow you to confidently start when working. The drill installed in it will no longer move to the side.
Through hole
From the lips of some masters you can hear the word “passage”. Because the drill completely penetrates the workpiece in its movement. In fact, this is the easiest operation. But special attention needs to be paid to the final stage.
When leaving the workpiece, the drill can not only damage the surface of the workbench, but also break itself from the impact. To avoid this, you need to do the following. Either place the part above the through hole in the workbench, or place a wooden spacer under it.
Through hole in a metal workpiece Source onarzedziach.pl
Also, a sharp exit from the part creates a hart (burr) on its reverse side. To prevent this from happening, it is necessary to reduce the drill speed at the final stage to the very minimum. This technique will help if you need to make a through hole in the metal, when the part cannot be dismantled and clamped in a vice. That is, drilling occurs at its location.
Blind hole
To ensure that the drill does not go right through the part, but stops at the required depth, two methods are used. A special stop is attached to the drill, positioning it at a given distance from the cutting edge. The device usually has the form of a sleeve.
Or the drill has a movable pin in the chuck area. It is clamped with a screw so that its end creates an emphasis on the workpiece. Not allowing the drill to penetrate deeper than the measured distance.
Drill with stop Source icover.ru
If a machine is used to drill a blind hole in metal, it usually has a ruler. Knowing the required depth, the operator stops the mechanism at the right moment. There are machines in which such an operation is fully automated. And the most serious inconvenience in such work is that it is periodically necessary to remove chips from the hole.
Safety and tips
Before drilling a hole in metal, it is necessary to ensure safety measures. First of all, you need to pay attention to work clothes. It should not contain elements that could get under the rotating parts of the tool.
During operation, chips can fly in different directions. It is necessary to protect your eyes from it by wearing safety glasses. Before drilling itself, check how securely the part is secured in a vice or how tightly it fits to the surface of the workbench.
The drill, approaching the surface of the metal, should already be rotating. This avoids premature dulling. Also, do not stop the drill while removing the drill from the hole. You just need to slow down. Otherwise, the tool will either jam or break.
When the cutting edge penetrates into the metal with great difficulty despite the applied efforts, this indicates that the hardness of the machined surface is much greater than that of the tool. You need to take a drill with a carbide tip. And set the drill to the lowest speed.
Boring
If the diameter of the hole exceeds the diameter of standard drills or countersinks, then the hole is bored. Boring is also used when machining holes with uneven allowance or with a non-linear generatrix.
Depending on the purpose, turning boring cutters are distinguished for processing through and deep holes. For turning boring rod cutters, the cantilever part is made round, and the rod for fastening the cutters is square; With such cutters you can bore holes with a diameter of 30.65 mm. To increase vibration resistance, the cutting edge of the cutters is made along the axis of the rod.
On turret lathes, round boring cutters are used, which are mounted in special mandrel holders (Fig. 4.30).
The shape of the front surface and all angles of the boring cutters (except for the back one) are taken to be the same as those of the cutters used for external turning. The cutting angles of boring cutters can be changed by setting the cutting edge of the cutters relative to the longitudinal axis of the part (above or below the axis).
When boring, the cutter is in more difficult conditions than during external longitudinal turning, since the conditions for chip removal, coolant supply and heat removal worsen.
A boring cutter, compared to a turning cutter, has a smaller cross-sectional area of the holder and a larger overhang, which causes the cutter to be pressed out and contributes to the occurrence of vibrations; Therefore, when boring, as a rule, smaller chips are removed and the cutting speed is reduced.
When rough boring steel, the cutting depth is up to 3 mm; longitudinal feed - 0.08. 0.2 mm/rev; cutting speed is about 25 m/min for high-speed steel cutters and 50.100 m/min for carbide cutters.
When finishing boring, the cutting depth does not exceed 1 mm, the longitudinal feed is 0.05. 0.1 mm/rev, cutting speed - 40.80 m/min for high-speed steel cutters and 150.200 m/min for carbide cutters.
Sources:
https://www.inmet16.ru/sverlenie-otverstij/ https://moy-instrument.ru/instrumenty/tehnologiya-obrabotki-otverstij-na-tokarnyh-stankah.html
Briefly about the main thing
When drilling metal, you need to be able to choose the right working tool. You will need a powerful drill capable of performing operations at low speeds. You also need to stock up on either cobalt drills or drills with carbide alloy bits.
To make large-diameter holes, you need to have a conical stepped drill or a crown with carbide teeth. And if the metal being processed is very thick, then it is better to replace the drill with a stationary machine.
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