grind in

verb

(tr, adverb) engineering to make (a conical valve) fit its seating by grinding them together in the presence of an abrasive paste

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012