Drilling deep holes in metal

Deep hole drills. cannon, gun, ejector

A gun drill is a tool that drills through and blind holes, which differ in considerable depth. Holes of this type are made in shafts for various purposes, in spindles, as well as in other parts characterized by a significant length. For this purpose, not only cannon drills are used, but also, in particular, single-edged and double-edged drills with internal chip evacuation. Drilling with the help of the latter is characterized by low productivity, but at the same time, the deep holes performed are characterized by high purity, accuracy of geometric parameters and straightness.

Deep hole drilling process on a turn-milling center

Deep hole drilling in metal technology

Features of drilling blind holes in metal workpieces

Blind holes are drilled to a certain depth. There are the following methods to install it.

Using the rulers available on the machines.

Installation of bush stops on drills.

Limiting the length of drills using chucks with adjustable stops.

Photo: drill with an installed sleeve stop

Modern machines are equipped with automated feeding systems. With its presence, the technology of drilling blind holes in metal is greatly simplified. You just need to set the cutting parameters.

Note! When making long blind holes in thick workpieces, it is necessary to interrupt the metal drilling process several times to force the removal of chips.

Drilling technology for large and small holes

Drilling a hole in metal is a common technological procedure that can be performed using a variety of equipment. Work methods differ depending on the required depth, diameter, surface type, and the required accuracy.

Drilling technology for thick metal sheets

For drilling thick sheets of metal, either tapered (for holes with a diameter of up to 30 mm) or core drills (for holes of large diameters) are usually used. They are equipped with drilling machines or powerful drills. The main requirement is that the equipment must maintain the operating mode at the lowest speeds.

Photo: core drills for metal

The technology of drilling thick metal sheets with core drills is highly efficient. Energy costs are minimal. Holes after drilling with crowns are smooth and precise.

Metal hole drilling technologies used in industry

In industry, more complex types of metal drilling are used. Use massive two-handed drills and special metal drilling machines (portable and stationary).

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Let’s talk about the features of various metal drilling technologies in production.

Types of drills for metal and their sharpening technique

Above, we examined the basic type of drills. It only takes a little knowledge and practice to understand how corners are formed when sharpening. It is best to sharpen drills on a grinding machine with a hand-hand, in the worst case, you can use a universal sharpener. It is impossible to sharpen drills on an angle grinder: firstly, this contradicts safety precautions when working with this power tool, and secondly, due to the high rotation speed, the metal overheats and loosens, becoming soft.

When sharpening, the drill is placed on the handrail so that its cutting part is slightly raised. Turning the drill and moving the shank to the left, you need to ensure that the cutting edge is located strictly horizontally and parallel to the end of the circle. You need to sharpen the left and right edges alternately, removing a thin layer of metal and periodically cooling the drill in water.

If you simply fix the drill in the desired position and bring it to the emery, you will not be able to properly grind the back surface. Due to the fact that the whetstone is round, the occipital part of the edge is concave. This leads to rapid edge dulling and chip evacuation problems. To avoid this phenomenon, after touching the stone, the front part of the drill should be slightly raised, feeding forward and without releasing the pressure. This creates a convex flank surface, which takes up the cutting load much better.

Edge turning should be performed before removing sharp edges without chips or burrs. In this case, the removal on both sides should be uniform, which can be judged by the shape and position of the remaining bridge, as well as by the length of the edges themselves. If the web is misaligned, the drill will rotate eccentrically, which will increase the hole diameter. This effect can be used if a drill of the required diameter is not available.

When the main edges have been pulled out, the lintel is sewn. To do this, the drill must be placed on a handrail at an angle of about 45 ° and pressed with its back to the edge of the circle, without touching the cutting edge. On the lintel, two small notches up to 1/10 of the drill diameter are formed, which act as lead-in and centering edges.

A more specific type of drill is used for drilling thin sheet metal. When making a deep hole, the drill is first centered at the top, and at the exit is held by the ribbons of the spiral part. However, in thin metal, the apex goes right through before the ribbons hit the edges, making the hole ragged, misaligned, or oval.

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In such situations, it is better to use a feather drill with a centering nose. This can be made from a conventional metal drill by regrinding it in a certain way. Everything is done in the same way and with the same angles, but the edges are not turned from the top to the edges, but brought together towards each other. The drill must be sharpened against the edge of the stone, leaving the lintel intact. Seam the edges until the bridge forms a nose protruding 1–2 mm above the tops of the cutting part.

drilling, deep, holes, metal

The third type of drills for metal is tapered stepped. They have several cutting edges of different diameters, which allows you to make different sized holes with just one tool. However, despite the seeming versatility, it is quite difficult to find a really good step drill, and its cost will be at least 25. Another disadvantage is that such drills can be sharpened only on a specialized machine.

For drilling in cemented carbide and hardened steel, it is better to use concrete drill bits. Their sharpening is initially designed for crushing action, however, if you bring out the edges at an angle at the top of about 135 ° and sharpen them at an angle of 20 °, even in a very hard part you can easily make a neat hole.

How not to blunt drills

Violation of the drill operation mode leads to a loss of cutting qualities. This is due to excessive heating of its surface, which is caused by the force of friction.

When drilling holes, do not exceed the recommended speed. Most models of hand tools are not equipped with a spindle rotation adjustment mechanism, so there is only one way out. do not press the power button with all your might. The rotational speed of the drill can be assessed visually: if the spiral channels do not merge into one, the rotational speed does not exceed 1000 rpm.

When drilling holes in thick-walled workpieces, coolants must be used.

Features of drilling large holes

Drilling a large diameter hole is a challenge, even for an experienced turner. As mentioned above, a cone-step drill or a crown nozzle is used as a working tool.

An alternative way to drill a large hole in metal is to use multiple drills, going from smaller to larger.

Experts recommend using crowns. Despite the high cost of the procedure, it allows you to get more accurate holes.

Devices to facilitate the process

As a lubricant for drilling metal at home, use:

  • Technical Vaseline. for soft materials.
  • Soap solution. for aluminum.
  • Turpentine with alcohol. for silumin.
  • Blend of oils. for tool and alloy steels.
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Some craftsmen prefer to use a universal composition that includes laundry soap (200 g) and motor oil (20 g). The components are mixed and boiled until a homogeneous emulsion is obtained.

Drilling Deep Holes with Small Drill Bits

The use of industrial cutting fluids allows to increase the drilling speed of various types of metal. For example, when processing stainless steel, productivity increases by 30%. For cast iron, this parameter increases to 40%.

Can I use a victory drill

Pobedit is a hard alloy based on tungsten carbide and cobalt. Its hardness is comparable to diamond.

Victory soldering on drills is used for crushing hard materials: stone, brick or concrete. Considering the fact that drilling holes in metal is based on the principle of cutting, it is better to use classic tools made of tool steel.

Using a victorious drill for processing metal products will lead to quick wear of the brazing.

How and how to drill deep holes

Ensure that drilling by-products are removed in a timely manner. They can clog the channels and break the drill. A small workpiece can simply be turned over. the chips will fall out of the hole due to gravity. For massive parts, there are special devices with magnetic tips.

For household chores, it is better to purchase drill guides. It is a convenient support mechanism that fixes the tool in a fixed position, allowing you to drill holes with high precision.

In the absence of a guide, you must carefully monitor the perpendicularity of the drill. The slightest deviation can break the tool or damage the workpiece.

Marking the future hole

To improve the accuracy of work, pre-drilling technology is used. When offset from the center, notches are made using a chisel that guide the drill in the desired direction.

The template is useful when processing several workpieces For example, for simultaneous drilling of several sheets connected by a clamp.

To obtain an accurate hole located at a certain angle, special conductors are used. They are a small bar with hole templates. Conductors are used in many industries. Now there are many types, including:

  • waybills;
  • swivel;
  • universal;
  • sliding;
  • fixed.

Mode and speed selection

Beautiful and long chips indicate that the drilling parameters are correct.

How to drill a hole correctly

To obtain a high-quality hole, the master must know the features of the operation of the drilling tool, as well as the subtleties of surface preparation before work.