A flat steel plate drilled with holes of various sizes, each marked with the correct size or number into which small twist drills may be fitted to determine the size of their diameters. See also: Drill Bits. Found on https://www.encyclo.co.uk/local/20687
A flat steel plate drilled with holes of various sizes, each marked with the correct size or number into which small twist drills may be fitted to determine the size of their diameters. See also: Drill Bits.