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An annular cutter (also called as core drill, core cutter, broach cutter, Trepanning drill or cup-type cutter) is a hollow, multiple cutting edges cutting tool used to make/drill holes in ferrous and non-ferrous metals. An annular cutter cuts only an annular groove at the periphery of the hole and leaves a solid core or slug at the hole center.〔Metal Cutting Theory and Practice. David A. Stephenson, John S. Agapiou CRC Press, 02.12.2005. Page number 216.〕 Annular cutter is a substitute for slower, more expensive and less efficient Twist drills and Hole saws. The function of Annular Cutters is more or less same as a hole saw but differs in geometry and material. Annular cutters are faster, easier and are more accurate than the conventional twist drills or drill bits. An annular cutter or core drill removes the material from the metal to create cylindrical holes in a circular cross section. An annular cutter, unlike drill bits, cuts only on the periphery of the hole to be made. Annular cutters use almost the same method as concrete core drills, but are for metal drilling. An annular cutter is a multipoint cutting tool and is made from material like high speed steel and tungsten carbide tips. Annular cutters are available in different sizes generally starting from diameter 12 mm (1/2’’) to 200 mm (7 7/8’’) and larger if required. The length of the annular cutter can be achieved depending upon the thickness of the material to be drilled. In the market the lengths 30 mm, 55 mm, 75 and 110 mm annular cutters are popularly available. These sizes though vary from manufacturer to manufacturer. The annular cutter’s material should be harder than the material to be drilled. Therefore there are various types of material used to manufacture annular cutters, for example different types HSS and TCT material. Annular cutters are also called as core drills because, after drilling hole, the drilled material is ejected from the cutter in the form of a cylindrical blank, this blank is called a core. The first annular cutter was invented by Mr. Dough Hougen which he patented in 1973. The High Speed Steel annular cutter was invented in 1983 by Michael Beharry 〔United States Patent. Patent number 4516890. Filed 12.09.1983. USA.〕 and the tungsten carbide tipped annular cutter was invented in 1985 by Mikiya Toshio and Shoji Michihiro.〔United Kingdom Patent. Patent number 2167983-A. Filed 31.10.1985. UK.〕 Though people use annular cutters on conventional drilling machines like radial drilling machines or pillar drilling machine, it is not recommended because these machines have very high RPM which creates high tool breakage risk for annular cutters as they are hollow unlike solid twist drills. It is always recommended to use an annular cutter or core drill with a magnetic core drilling machine (also called as magnetic drill, magnetic base drilling machine, etc.) as these machines are slower. A magnetic drilling machine is ideally made for using annular cutters. == History == During the early 70s, Mr. Dough Hougen invented the Rotabroach annular cutters. During those days twist drill bits were so poplular that people were not in mood to accept a new idea of cutting holes with annular cutters. Hougen took the annular cutter to many drill bit manufacture but he got a dispappointing response, but when he took the annular cutters to the fabricators and construction steelworker they were very well interested in this concept because during those period the construction steelworker and fabricators used a The annular cutter made by Hougen were comparatively safe, the annular cutter won't break free, the workers liked the cutters but the annular cutter could not solve the heavy weight problem of magnetic drilling machine. Hougen later reinvented the magnetic drilling machine making it just 28 lbs (12.70 Kg.). The reinvention of the magnetic drilling machine with its portability also gave birth to high volume sales of annular cutters.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Annular cutter」の詳細全文を読む スポンサード リンク
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