Anonymous ID: e1659b June 8, 2018, 10:36 a.m. No.1669433   ๐Ÿ—„๏ธ.is ๐Ÿ”—kun   >>9473 >>9494 >>9548

>>1669412

Trepanning was the Medieval term for it. Trepanning is a term still used in metalworking for drilling tubular holes, like you would with a hole saw.

 

Trepanning is a drilling process that leaves a core. Trepanning is a deep hole drilling process that has broad application over many industries. In many cases, trepanning is meant to be a roughing operation to be honed for finish, or machined further. In other cases, the trepanned hole is fit for use 'as-drilled'.