Annular cutters are tools used for drilling hole, but instead of removing material from the metal plate with twist drills, annular cutters remove the outer ring of material from the metal plate. Annular cutters move more fast than twist drills and use less power than twist drills. However, annular cutters are only as efficient as if the tool revolutions per minute are set to the correct speed for the diameters of the annular cutter and the type of material being cut.
Using an RPM that is too fast for the material will lead to the teeth of the annular cutter overheating. Using an RPM that is too slow for the material will cause the annular cutter to rub against the metal plate instead of cutting it. The RPM must be matched with both the diameter and the material to ensure that the annular cutter function correctly.
How to Use Annular Cutters: Speed, Materials and Care
The diameter of the annular cutter and the RPM of the tool are related to one another because the cutter must maintain the same relative surface speed. The surface speed is the actual speed at which the annular cutter’s cutting edge travel. This speed is the same for a given material, regardless of the diameter of the cutter.
A small diameter annular cutter will spin at a high RPM to reach the same surface speed as a large diameter annular cutter spinning at a low RPM. Thus, the larger the diameter of the annular cutter, the smaller the RPM of the cutter has to be to maintain the same surface speed. The hardness of the material will impact the rate at which the operator should use the annular cutter.
Materials like stainless steel will work better at approximately half the rate of mild steel. This reduced rate helps to reduce the chance of the stainless steel becoming more harder by the cutting process. Aluminum plates work best at twice the rate of mild steel.
However, to cut aluminum efficiently with an annular cutter, flood coolant is required to prevent the aluminum from adhering to the teeth of the cutter. Cast iron can be cut using dry cutting methods with annular cutters. Dry cutting methods avoid the use of coolant because the coolant can cause a type of thermal shock to the cast iron.
The construction of the annular cutter have an impact upon the tooling costs and heat tolerance of the cutter. High-speed steel cutters are relatively affordable and work well for structural steel projects. However, cobalt cutters work better for stainless steel projects because they can better tolerate the heat produced when cutting stainless steel.
Carbide-tipped cutters can cut at higher speeds and have longer lasting tools, especially when cutting abrasive materials. However, carbide-tipped cutters cost more money and require more steady machining machines to function proper. In these cases, the longer lasting tool is less costly per unit of work performed if there are deep holes to drill in the metal plate.
The depth of the material being cut will impact the way in which the annular cutter is used. Annular cutters are rated for specific depths of penetration. An annular cutter rated for one inch of penetration may work on thin metal plate.
However, attempting to drill into a three inch thick plate of metal may cause the annular cutter to flex and bind into the metal. Longer annular cutters are available for deep penetration holes. However, the longer the annular cutter the less rigid the cutter will be.
Thus, a shorter annular cutter should be used for deep holes so that the cut is kept straight and vibration is reduced. There are steps that can be taken to protect the annular cutter. Using cutting fluid will extend the life of the annular cutter when cutting steel.
However, many people will forget to use cutting fluid for the annular cutter when they are in a hurry. Using a pilot pin will center the annular cutter prior to the teeth of the cutter making contact with the metal. The pilot pin will prevent the cutter from moving across the metal plate.
Additionally, the magnetic base of the drill should always be seated on the metal workpiece to prevent the drill from shifting during cutting operations. Each of these steps will help to prevent the failure of the annular cutter. There are some problems with the annular cutter that can be recognized.
For instance, blue or discolored metal chips indicate that the RPM of the cutter was too high for the material. Thick and powdery metal chips may mean that the cutter was rubbing against the material instead of cutting it. Squealing sounds or chatter from the annular cutter may mean that the arbor components are loose or the magnetic base is not making sufficient contact with the metal workpiece.
By monitoring the chips and the sound the cutter makes while in operation, the operator can make corrections to the cutting operation. In each of these instances, the operator can protect the annular cutter from damage. Annular cutters may cost more money than twist drills.
However, annular cutters save time when cutting holes that are larger than half of an inch. Additionally, annular cutters will produce a clean slug of metal and create a smooth cut in the metal plate. Furthermore, using the annular cutter will eliminate the necessity of step-drilling when compared to using twist drills.
Thus, although the annular cutter costs more money, it is more efficient when cutting holes in metal plates as large as half of an inch or larger in diameter. The efficiency will be experienced with the right selection of the speed and the feed of the cutter. Use the provided chart to determine the specific reference points for the speed and the feed for the material being cut.
