No. 97-1026 Argued October 24, 1997 Decided December 12, 1997 Marc B. Gursky argued the cause and filed the briefs for petitioners. Frederick C. Havard, Supervisory Attorney, National Labor Relations Board, argued the cause for respondent, with whom Linda R. Sher, Associate General Counsel, and Aileen A. Armstrong, Deputy Associate General Counsel, were on the brief. Thomas C. Keeney argued the cause for intervenor Brown Sharpe Manufacturing Company, with whom William R. Powers, III was on the brief