B bit

B bit

[′bē ‚bit]
(mining engineering)
A nonstandard core bit no longer in common use except in drilling deep boreholes to sample gold-bearing deposits in South Africa; the set outside and inside diameters are about 2¹⁄₁₆ and 1⅜ inches (52 and 35 millimeters), respectively.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.