OAK INDUSTRIES <OAK> TO BUY REXNORD <REX> UNIT Oak Industries said it signed a definitive agreement to buy the stock of Rexnord Inc's Railway Maintenance Equipment Co unit, for an undisclosed sum. The company said Railway Maintenance had 1986 revenues of 16 mln dlrs. Oak said the acquisition is part of its two-tier strategy of buying releated and unrelated businesses. Oak had a tax loss carryforward of 125 mln dlrs at the end of 1986.