The present invention relates to an abrasive-bladed or, in particular, diamond-bladed cutting wheel. More particularly, the invention relates to a cutting wheel bladed on the outer periphery of a base wheel with abrasive particles such as diamond particles and particularly suitable for cutting sintered magnets of a rare earth-based alloy.
It is usual that a sintered block of a rare earth-based alloy magnet is fabricated into desired forms of magnets by cutting with a diamond-bladed cutting wheel. The diamond-bladed cutting wheels currently under practical use for this purpose include two types as grossly classified. A cutting wheel of the first type is formed by bonding fine abrasive particles to the inner periphery of an annular thin base wheel which is a so-called internal-bladed cutting wheel and a cutting wheel of the second type is formed by bonding abrasive particles to the outer periphery of a circular thin base wheel which is a so-called outer-bladed cutting wheel. FIGS. 1A, 1B and 1C illustrate an internal-bladed cutting wheel 1 consisting of an annular base wheel 3 and a cutting blade 4 having a thickness t formed on the inner periphery of the annular base wheel 3. It is a trend in recent years that the major current of the cutting technology for rare earth magnets is to use the cutting wheels of the latter type in view of the higher productivity obtained therewith.
When a large number of magnet products of definite dimensions are produced by cutting a large sintered block of a rare earth-based magnet alloy using a diamond-bladed cutting wheel, one of the major factors to determine the production cost of the magnets is the correlation between the thickness of the cutting wheel and the material yield of the workpiece, i.e. the sintered block of the magnet alloy. Namely, it is important that the cutting wheel used has a thickness as small as possible and the cutting work is conducted with high accuracy so as to reduce the material loss by cutting and to increase the number of the finished magnet pieces taken from a single block.
Needless to say, a diamond-bladed cutting wheel having a small thickness can be prepared only by using a base wheel of a small thickness. In this regard, the internal-bladed cutting wheel is advantageous as compared with the outer-bladed cutting wheel because an internal-bladed cutting wheel is used under rotation by outwardly tensioning the outer periphery of a thin annular base wheel in a slackfree fashion something like a drumhead so that the thickness of the base wheel can be small enough. The base wheel of an internal-bladed cutting wheel can be formed from a thin sheet of a stainless steel having a thickness of about 0.1 mm to which a peripheral cutting blade of 0.25 to 0.5 mm thickness is provided on the inner periphery of the annular base wheel. The base wheel of an outer-bladed cutting wheel under practical use, on the other hand, is formed from an alloy tool steel of the grades SK, SKS, SKD, SKT, SKH and the like specified in a JIS standard. A base wheel made from the above mentioned alloy tool steel and having such a small thickness, however, does not have a high mechanical strength suitable for cutting of sintered rare earth magnet blocks having a high hardness so that the cutting wheel under working unavoidably causes warping and undulation not to give a high cutting accuracy. Moreover, sintered rare earth magnet blocks in general have a higher hardness than that of the above mentioned alloy tool steels so that the base wheel is eventually damaged by the chips formed by cutting from the sintered block and jammed between the base wheel and the workpiece to decrease the durability of the cutting wheel or to increase warping or undulation of the base wheel.
USPTO Backgrounds
USPTO Backgrounds