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An annular cutter (also called a core drill, core cutter, broach cutter, trepanning drill,hole saw, or cup-type cutter) is a form of core drill used to create holes in metal. An annular cutter, named after the annulus shape, cuts only a groove at the periphery of the hole and leaves a solid core or slug at the center. [1]
An annular cutter is a more expensive and efficient alternative to spiral drill bits and standard hole saws. An annular cutter is similar to a hole saw but differs in geometry and material. The two most common types are high-speed steel (HSS) and tungsten carbide tipped (TCT).
Like a hole saw, but unlike a spiral drill bit, an annular cutter cuts only the periphery of a hole, leaving a circular "slug" at the center.[ citation needed ]
Annular cutters are best used with a drill press or magnetic drilling machine, both for their stability against high torque forces created by such a drill bit and lower RPMs compared to other types of drills.
The annular cutter was patented in 1973. [2] The high-speed steel type was patented 1983, [3] and tungsten carbide tipped in 1985. [4]
As an annular cutter cuts only on the periphery of the hole to be made, which cuts and removes the complete material of the hole, annular cutters are considered to be 3 to 4 times faster than conventional drill bits.[ citation needed ] Also, while using a twist drill bit or metal hole saw, one has to do pre-drilling and step-drilling operations for bigger diameter holes, whereas an annular cutter requires no pre-drilling and step-drilling. It is a one-shot drilling operation.
The annular cutters have fewer teeth and less wear, therefore with an annular cutter holes can be made at a higher or faster cutting speed and a faster feed rate of the drilling machine. [5]
Because annular cutters do not have to drill/cut through the complete workpiece, they require less thrust and thus less energy to drill through material. [6]
The cooling of annular cutters is internal. The internal lubrication is provided through a hole with the help of a pilot pin. Internal lubrication makes the annular cutter faster and more efficient for deep-hole drilling. [6]
As the annular cutters require very low RPM (from min 50 RPM), these cutters are often used with light-duty drilling machines or portable magnetic base drilling machines. [6]
Annular cutters come in a variety of sizes. Annular cutters are available from 12 mm (1/2’’) in diameter to 200 mm (7 7/8’’) and larger. Depths of 30 mm, 55 mm, 75 and 110 mm are commonly available. Annular cutters start from 12 mm diameter up to 150 mm diameter and more if required. Various cutting depths (lengths) of annular cutters can be sourced depending on the requirement. [6]
HSS annular cutter can be easily re-sharpened on a grinding machine and can be reused for drilling. Re-grinding can be done until the desired cutting length is available on the annular cutter. [6]
The types of core drills are categorized by the material used to manufacture them: Primarily a metal core drill is made from High-Speed Steel and Tungsten Carbide Tips. So commercially the types of core drills are HSS core drills and TCT core drills.[ citation needed ]
HSS core drills are made from high-speed steel material. These are the most popular core drills or annular cutters in the market. HSS core drills are cheaper for smaller diameters i.e. 40 mm. The HSS core drill, unlike the TCT core drills, has the ability to re-sharpen. HSS core drills are re-sharpened and used until the desirable length is remaining. HSS core drills have a longer service life, and high heat resistance: the characteristic of HSS core drills is that drilling with these core drills can be done without the use of excessive force.[ citation needed ]
The HSS Standard core drills are made from M2 steel. These core drills are one of the most popular core drills in Western countries due to their cost and resharpening advantage. The Standard HSS core drills are used to drill Mild and Structural steel, Aluminium, Stainless steel of lower BHN., etc.[ citation needed ]
The HSS Cobalt are core drills made from M42 Steel. These core drills have 8% Cobalt in HSS. These core drills are harder than the Standard HSS core drills which gives better performance to drill harder material. A high percentage of Cobalt in HSS makes it faster, stronger, and durable.[ citation needed ] Cobalt HSS core drills are used to drill materials like Structural Steel, Stainless Steel, Cast iron, etc.[ citation needed ]
The HSS core drills with Hard Coating are core drills with a coating on them, generally TiN Coating. This makes the core drills more resistant to heat, longer tool life, and even removal of chips. These core drills are gaining a lot of popularity over the Standard HSS core drills these days. These core drills are used Structural steel, Stainless steel, etc.[ citation needed ]
Tungsten carbide tipped (TCT) core drills have tungsten carbide on their tips, a very hard material suitable for cutting through tougher materials. TCT core drills are more expensive than HSS core drills but are faster and more efficient in making larger holes. TCT core drills are cheaper for bigger diameters i.e. above 41 mm. Tip breakage is more likely than with HSS core bits, and TCT bits may not be re-sharpened.[ citation needed ]
A Standard TCT core drill has tungsten carbide tips. These types of core drills are now available in a vast range of diameters, for up to 150 mm. These are popularly used core drills on magnetic core drilling machines. These core drills are popularly used to drill materials like railway tracks, structural steel, stainless steel, cast iron, etc.[ citation needed ]
The TCT core drills with Hard Coating are core drills with a coating on them, generally TiN Coating. This makes the core drills more resistant to heat, longer tool life, and even remove of chips just like the advantage of HSS core drill. The biggest advantage of hard-coated core drills is that these cutters are very good for cutting larger diameters on hard material. These core drills are popularly used to drill materials like corroded or weathered material, structural and stainless steel.[ citation needed ]
"Weldon shank" annular cutters have 2 flats and this is the traditional method adopted by many of the popular magnetic drill manufacturers. "Weldon shank" annular cutters fix in the chuck by tightening grub screws in the two flat areas.
"Universal shank" annular cutters have one flat and three quick connect grooves. This is also a popular method for using annular cutters into mag drills quickly, without any strain of tightening grub screws. mostly "universal shank cutters" can be used in "weldon -shank machines, whereas weldon-shank annular cutters can't use in "one-touch" machines without the help of an extra adapter. While using "universal shank cutters" in "weldon shank" machines, the tightening area (flat area) is only one, which is also not 100% sufficient to tighten both screws.
Annular cutters can also be used to make holes in pipes and tubes without dimpling and deburring.
To make a hole in a tube or pipe easily an annular cutter should be used with a magnetic base drilling machine and a tube/pipe clamping device. The tube clamping device is a metallic device that is clamped on the tube with an adjustable chain. After clamping the device the magnetic drilling machine is placed on the device, which gets clamped to the device by switching on its magnet.
With the help of magnetic drilling machines' proper RPM, the annular cutter makes a perfect hole in the tube.
Generally, a HSS annular cutter is used to make holes in tubes and pipes, as the TCT annular cutters have more chances of cutting teeth breakage due to curved surfaces of tubes and pipes.[ citation needed ]
As annular cutters are hollow there is no dead zone resistance. The cutting takes place only on the periphery of the hole to be made. Annular cutters distribute the load equally on the periphery of the hole with its multiple cutting edges, thus the required thrust and energy are also much less comparatively. [7]
Annular cutters are also manufactured with special grade, especially for drilling railway tracks. Rail annular cutters are designed for railroad rail drilling operations. [8] The rail annular cutters with special manufacturing technology are made to drill very hard and corroded material like rail. Rail annular cutters are available in HSS and TCT types, though TCT rail cutters are more popular worldwide.
HSS core drills are cheaper than the TCT core drills for smaller diameters up to 40 mm, while TCT core drills are cheaper than HSS for diameters above 41 mm.
Once the HSS cutter loses its sharpness, it can be re-ground on a grinding machine and can be used again. Similarly, re-grinding the TCT core drills is possible, but takes more time.
The chances of defects in TCT core drills are higher because the tungsten carbide tips are glued to the core drill and when the core drill falls down or crashes on the material, the chances of tip breakage are higher. HSS cutters on the other hand are less likely to fail that way since they are completely made out of a single material.
TCT cutters are used to cut harder materials with ease. Especially for boring larger diameter holes in hard materials, TCT core drills can be used to great success. Comparatively, HSS core drills are more often used for drilling softer materials and for small-diameter hole sizes.
The teeth on TCT core drills are harder than HSS, allowing them to cut more difficult materials.
The biggest disadvantage of a core drill or annular cutter is that it can not drill blind holes. A core drill, due to its hollow geometry, can only make it through holes. The cost of a core drill is high compared to a twist drill, but the cost per hole made with the core drill is less as compared to twist drills, this is because a single core drill makes 5 to 10 times more holes than a twist drill. [9]
Annular cutters are more fragile than a drill bits of the same diameter and may thus shatter more easily. They are also more difficult to remove if stuck, as they have a larger contact area with the workpiece than a regular drill bit.
The use of lubricant or coolant is important with any type of annular cutter to deliver longer life from the cutter. TCT annular cutters require coolant not a lubricant, and HSS annular cutters required cutting oil not coolant.
Overhead drilling with liquid lubricants can cause damage to the motor of the drilling machine. High performance cutting paste can be used in both overhead and normal orientation and is suitable for both HSS and TCT cutters as well as for thread cutting taps and dies.
The ejector pin (also called a pilot pin) has three major functions:[ citation needed ]
The magnetic drilling machines are provided with speed gears and some machines are also equipped with variable speed control. As per the diameter of the annular cutter and the type of annular cutter the speed of the magnetic drilling machine has to be set.[ citation needed ]
The formula for calculating the speed is:
d = diameter of the annular cutter in mm.
v = cutting speed of the annular cutters.
Trade-offs between HSS and TCT annular cutters include: [10]
The router is a power tool with a flat base and a rotating blade extending past the base. The spindle may be driven by an electric motor or by a pneumatic motor. It routs an area in hard material, such as wood or plastic. Routers are used most often in woodworking, especially cabinetry. They may be handheld or affixed to router tables. Some woodworkers consider the router one of the most versatile power tools.
A drill is a tool used for making round holes or driving fasteners. It is fitted with a bit, either a drill or driver chuck. Hand-operated types are dramatically decreasing in popularity and cordless battery-powered ones proliferating due to increased efficiency and ease of use.
A drill bit is a cutting tool used in a drill to remove material to create holes, almost always of circular cross-section. Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. In order to create holes drill bits are usually attached to a drill, which powers them to cut through the workpiece, typically by rotation. The drill will grasp the upper end of a bit called the shank in the chuck.
High-speed steel is a subset of tool steels, commonly used as cutting tool material.
Drilling is a cutting process where a drill bit is spun to cut a hole of circular cross-section in solid materials. The drill bit is usually a rotary cutting tool, often multi-point. The bit is pressed against the work-piece and rotated at rates from hundreds to thousands of revolutions per minute. This forces the cutting edge against the work-piece, cutting off chips (swarf) from the hole as it is drilled.
A reamer is a type of rotary cutting tool used in metalworking. Precision reamers are designed to enlarge the size of a previously formed hole by a small amount but with a high degree of accuracy to leave smooth sides. There are also non-precision reamers which are used for more basic enlargement of holes or for removing burrs. The process of enlarging the hole is called reaming. There are many different types of reamer and they may be designed for use as a hand tool or in a machine tool, such as a milling machine or drill press.
The phrase speeds and feeds or feeds and speeds refers to two separate velocities in machine tool practice, cutting speed and feed rate. They are often considered as a pair because of their combined effect on the cutting process. Each, however, can also be considered and analyzed in its own right.
In machining, a tool bit is a non-rotary cutting tool used in metal lathes, shapers, and planers. Such cutters are also often referred to by the set-phrase name of single-point cutting tool, as distinguished from other cutting tools such as a saw or water jet cutter. The cutting edge is ground to suit a particular machining operation and may be resharpened or reshaped as needed. The ground tool bit is held rigidly by a tool holder while it is cutting.
Milling cutters are cutting tools typically used in milling machines or machining centres to perform milling operations. They remove material by their movement within the machine or directly from the cutter's shape.
Burrs or burs are small cutting tools; not to be confused with small pieces of metal formed from cutting metal, used in die grinders, rotary tools, or dental drills. The name may be considered appropriate when their small-sized head is compared to a bur or their teeth are compared to a metal burr.
A lathe center, often shortened to center, is a tool that has been ground to a point to accurately position a workpiece on an axis. They usually have an included angle of 60°, but in heavy machining situations an angle of 75° is used.
A tipped tool is any cutting tool in which the cutting edge consists of a separate piece of material that is brazed, welded, or clamped onto a body made of another material. In the types in which the cutter portion is an indexable part clamped by a screw, the cutters are called inserts. Tipped tools allow each part of the tool, the shank and the cutter(s), to be made of the material with the best properties for its job. Common materials for the cutters include cemented carbide, polycrystalline diamond, and cubic boron nitride. Tools that are commonly tipped include milling cutters, tool bits, router bits, and saw blades.
In the context of machining, a cutting tool or cutter is typically a hardened metal tool that is used to cut, shape, and remove material from a workpiece by means of machining tools as well as abrasive tools by way of shear deformation. The majority of these tools are designed exclusively for metals.
A modern core drill is a drill specifically designed to remove a cylinder of material, much like a hole saw. The material left inside the drill bit is referred to as the core.
A hole saw, also known as a hole cutter, is a saw blade of annular (ring) shape, whose annular kerf creates a hole in the workpiece without having to cut up the core material. It is used in a drill. Hole saws typically have a pilot drill bit (arbor) at their center to keep the saw teeth from walking. The fact that a hole saw creates the hole without needing to cut up the core often makes it preferable to twist drills or spade drills for relatively large holes (especially those larger than 25 millimetres. The same hole can be made faster and using less power.
A cold saw is a circular saw designed to cut metal which uses a toothed blade to transfer the heat generated by cutting to the chips created by the saw blade, allowing both the blade and material being cut to remain cool. This is in contrast to an abrasive saw, which abrades the metal and generates a great deal of heat absorbed by the material being cut and saw blade.
In the oil and gas industry, a drill bit is a tool designed to produce a generally cylindrical hole (wellbore) in the Earth’s crust by the rotary drilling method for the discovery and extraction of hydrocarbons such as crude oil and natural gas. This type of tool is alternately referred to as a rock bit, or simply a bit. The hole diameter produced by drill bits is quite small, from about 3.5 inches (8.9 cm) to 30 inches (76 cm), compared to the depth of the hole, which can range from 1,000 feet (300 m) to more than 30,000 feet (9,100 m). Subsurface formations are broken apart mechanically by cutting elements of the bit by scraping, grinding or localized compressive fracturing. The cuttings produced by the bit are most typically removed from the wellbore and continuously returned to the surface by the method of direct circulation.
Cemented carbides are a class of hard materials used extensively for cutting tools, as well as in other industrial applications. It consists of fine particles of carbide cemented into a composite by a binder metal. Cemented carbides commonly use tungsten carbide (WC), titanium carbide (TiC), or tantalum carbide (TaC) as the aggregate. Mentions of "carbide" or "tungsten carbide" in industrial contexts usually refer to these cemented composites.
A magnetic drilling machine is a portable drilling machine with a magnetic base. It can use twist drill bits, annular cutters, milling cutters, and other rotary cutters. With suitable bits it can also tap threads, ream, and countersink. Its combination of a stable magnetic base and low RPM help resist or reduce torque forces created by large diameter bits. Magnetic drilling machines with reversible motor and variable speed controls can also perform operations like tapping, countersink and reaming. A magnetic drilling machine with a cross table base can also perform light milling.
A Rail Drilling Machine is a type of portable drilling machine specialized for drilling holes in rails. Rail Drilling Machines are also popularly called as Rail Drills, Portable Rail Drill, Rail Core Drilling Machines, etc.