In NLRB v. Joclin Mfg. Co., 314 F.2d 627, 631-32 (2 Cir. 1963), we recognized that the Board's discretion in determining whether or not to hold a hearing was not unfettered, but we held that it could condition the right to a hearing on the existence of substantial and material issues: "[This] requirement [is] not only proper but necessary to prevent dilatory tactics by employers or unions disappointed in the election returns."