Bits or Wicks for Metal?

Wicks or drills are cutting tools for drill or lathe. These tools perform a machining mode called drilling which consists of creating holes in different metallic materials. There are diamond bits used to cut materials such as ceramics, porcellanites, etc.

A characteristic of the wicks is that they have a helical body through which the chip comes out.

The tool is used with machining lubricants to maintain its useful life. Chip formation is determined by the material of the part you need to drill, the geometry of the drill bit, the cutting speed and to a certain extent by the type of lubricant used. Chip shape and length are acceptable as long as you can evacuate them effectively.

The propeller of the drill has the objective of evacuating the chip but also has another function that is to cut and dismember in smaller pieces the residues coming from the perforation of metallic materials. Due to the metals’ physical characteristics, the chip tends to come out of the propeller in loops which if not segmented by the same, would increase the friction of the tool against the piece to be drilled, producing the following undesirable effects:

  • As the friction increases, the working temperature increases which cause the material to be hardened and hardened.
  • As a result, the service life of the drill bit is shortened, as it is made of temperature hardened material.
  • For these reasons, the importance of efficient chip evacuation and there is an emphasis in the predominant use of coolant.

Elements of a Drill Bit

There are countless bits or wicks with different applications, but they differ in their technical characteristics which arise to be able to drill in different materials.

Total bit length: There are extra short, short, normal, long and extra long bits. The latter is used with a bench drill to drill deep into a surface and that the drill does not damage or damage the hole.

Cutting Length: It is the maximum depth that can be drilled with a wick and is defined by the useful length which is determined by the length of the propeller.

Cutting Diameter: It is the diameter of the hole obtained with the drill bit.

Cutting Angle: The normal cutting angle in a drill bit is 118º at the tip, but there are also 135º bits so that the higher the contact with the material, the wick is self-centered and does not slip on the surface.

Handle Diameter and Shape: The handle of a drill bit can be cylindrical, triangular or conical. The cylindrical stem is the most common, but you should know that there is a subtype that is the reduced handle. It consists of a reduction in the size of the handle in drills whose diameter exceeds 10 mm or 13 mm. It is the process to do so you can use a drill bit in mandrels of the above measures.

Drill bits

As for the triangular handle, it is a drill with notches in the surface that are in contact with the chuck to the ends so that the tool does not slip. It is styled to make this modification in strands intended to drill tough metals, such as alloy steels, matrices, etc.

Finally, there is the conical shank which has the particularity of being positioned on a special drill chuck, usually used to drill deep holes and a significant thickness.

Helix angle: The wick depends on the material you drill; it may have a particular aspect of cutting the chip and evacuate it. There is a series of letters to identify the application and the angle of the drill: N is the angle of the propeller of 30º for general use. W corresponds to the angle 40º/45º intended for machining Aluminum and long chip materials. The H type, known as the slow helix for its long helical pitch at an angle of 15º/20º. It is ideal for bronze and other materials whose chip is of high volume.  Finally, there is the S-type helix with a 35º angle. At first sight, you can notice the highlight of the quality of having a solid groove for quick chip removal; this type is perfect for stainless steels.

Getting the best drill bit set is definitely a big challenge whether you’re a simple DIYer or a professional handyman. Read our Drill Bits Buyers Guide to get more information on which drill bit set to buy.

Wick Constituent Material:

  • High-Speed Steel (HSS): for drilling low to medium hardness steels.
  • Tungsten Reinforced High-Speed Steel (HSS M2): More resistant than the previous one, it perforates high resistance alloy steels.  It is a more economical option against 5% cobalt wicks.
  • High-Speed Steel with 5% Cobalt (HSS Co 5%): High-speed steel is reinforced with 5% cobalt for a better performance against hard to machine materials.
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    High-Speed Steel with 8% Cobalt (HSS Co 8%): In this case, the reinforcement in the HSS reaches 8% to achieve the highest thermal resistance according to the American standard M 42.
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    Hard Metal (tungsten carbide): It is the material for rotating cutting tools, as it has advantages that stand out against high-speed steel, such as its hardness, resistance to wear and heat, rigidity and better cutting edge.  In the market, there are usually two types of bits with this material. On the one hand, there are the integral wicks, made entirely of tungsten carbide and are used in bench drilling machines. The material has very little flexibility, and the least vibration runs the risk of breakage. Drills manufactured with hard metal are more expensive than the common HSS drills, but their application is on materials that are extremely hard to drill.On the other hand, there are the drills with a hard metal plate in the tip. Its helical body up to the handle is produced in high-speed steel. It fulfills the same functions as an integral one, but it is economical, and its useful life is short. It is determined by the edge and the permanence of the tungsten plate in the tip.

Three Modes of Production of the Wicks

Different types of wicks

Laminated drills: their confection is carried out from a metallic piece. One side has a cylindrical sector (that later will be the end of the drill), and the other side has a flat part whose thickness is smaller to the other sector. Then, through a laminating machine (hence its name) takes the flat portion and gives it the helical shape by twisting it. They are very economical drills. Therefore their performance is very low. The cutting tip is not self-centering (split point).

Rectified drills: these drills come from a cylindrical metal piece whose propellers are achieved by grinding the metal with a stone. The rectification process is more exact than the lamination process and gives this drill a higher quality than the previous one with a higher yield. Also, it does not have a split point.

Milled and Ground Drills: these are from a cylindrical piece where it can acquire the propellers by grinding the metal with a stone. And then, a milling cutter is used to make recesses in the propeller. It facilitates the evacuation of chips and at the same time providing aid to progress in drilling. The quality of these drills allows the user to give superior performance to the other two and a better finish. The cutting tip is self-centering at an angle of 135º.  All wicks for professional use are constructed this way.

Finishing: A layer of black oxide or nickel’s application start from the cutting point to the handle depending on the use and application of the wick.  Usually, these finishes are to avoid tool rust, and the choice of one or the other is a cultural matter of the markets. In some countries the glossy finish wick has a higher quality status than the black finish wick, in others the opposite is true.

There are also coatings that are usually partial, but their function is to provide further durability to a drill bit, give better performance, and to avoid premature wear. Also, it facilitates the separation between the material to be machined and the cutting tool, and finally thermal insulation. Among them are the wicks with titanium nitride coating, with its characteristic yellow color, and those of TiAlN (titanium aluminum) for dry drilling in machining centers controlled by a computer.

However, one disadvantage of the coating is the impossibility of sharpening the wick once the edge is lost because in doing so, the performance of the tool decreases.

Special Bits or Highlights

Refrigerated drills: These are hollow drills in which the coolant passes through its interior and goes directly to the cutting point. They are used to evacuate swarf quickly and in conditions where it is necessary to lower the temperature arising from machining drastically.

Centring Drill Bit: This drill bit is used to drill a part to be used in a lathe if it is lightweight, the part to be machined is usually left as a counterpoint. If the piece is heavy, the function of the drill bit will be to make the hole for a tailstock to enter.

Drill Bit for Magnetic Base Drills: These drills have a double cutting geometry for perfect centering of the tool. The thermal treatment gives them a longer useful life. Also, they are capable of drilling with superior performance to high-speed steel drill bits and morse cone bits.

Its operation is detailed below:

1) The pilot guide rests on the material to be drilled, and the drill bit approaches until the beginning of the drilling.

2) The ring drill pierces a ring on the material, and the pilot guide remains on the undrilled material.

3) The pilot guide ejects the excess cylinder. At the end of the operation, the material core is expelled by a pin driven by the force of a spring. This pin also serves as a centering point at the start of the operation and as a flow valve for the lubricating oil.

Conical wicks for plates: Its function is characterized by making holes of exact diameter in metal sheets. The most used are the staggered ones because they have in their body the measurements of the holes to be produced.

Summary
Bits or Wicks for Metal
Article Name
Bits or Wicks for Metal
Description
Wicks or drills are cutting tools for drill or lathe. These tools perform a machining mode called drilling which consists of creating holes in different metallic materials.
Author
Publisher Name
Jack Noelsson
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