I have often marvelled at the fineness and regularity of line produced in Tsuba with ito sukashi.   Question: How did they get such a fine and controlled piercing?   I've been told various tales over the years, but none of them seem to fit the bill.   e.g. A London Nihon-To dealer once told me that the designs were cut larger and hammered tightly to a spring steel shim which acted as the spacer, the tsuba would later be heated and upon expansion, the shim removed.   A Sotheby's Rupert