Abstract: The grinding effects of small diameter cup CBN wheel which monorail grit is wrapped by metal layer bond (it is named monorail grit CBN quill) in face grinding of bottom of grooves are discussed. There is wheel self-dressing of monorail grit CBN quill in the grinding process. The flank wear, edge chipping, crack, breaking and fall off of CBN grits are happened in succession. The grinding force of monorail grit CBN quill changeful characteristics of low–frequent and high-frequent fluctuation, which is the integrated function of CBN grit being blunt during the flank wear and subsequently the blunt grits occurring chipping and breaking. The process is dominated by the performance of CBN grit and state of its cutting edge. High-toughness polycrystalline CBN grit (BORAZON550, GE type) will keep the sharpness of monorail grit CBN quill, prolong the serve time of single grit, has obvious group-effect when new grit with low protrusion height add to grinding process and grinding force has obvious low-frequent fluctuation. It will be processed continuously that single-crystal CBN grit (BORAZON500, GE type) is breaking and chipping and accordingly new grit cutting edges join to grinding process, as the results, grinding force will show high-frequent fluctuation obviously.

Key words: CBN grit chipping and breaking, CBN quill, Face grinding, Grinding force, Monorail grit