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:
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.
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:
Three Modes of Production of the 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.