A knife-edge shank is a ring band whose cross-section tapers from a flat or slightly rounded base to a sharp central ridge along the upper surface, producing the visual impression of a narrow blade running around the finger. The profile narrows the visible upper surface of the band to a single line, which makes a centre stone appear to float above a near-invisible support and which is favoured for solitaire designs intended to maximise the apparent size of the diamond. It is sometimes catalogued under the trade term peaked shank.

Profile and metalwork

The shank is normally executed in 18-carat gold or platinum at a base width of 1.6 to 2.2 millimetres, with the upper ridge brought to a controlled sharpness rather than a true edge so that the ring remains comfortable on the finger. Hand-fabricated knife-edge shanks are filed and polished to the apex, then hardened slightly through work-hardening or careful reflowing of the alloy at the ridge to resist deformation in wear. Cast shanks must be finished by hand at the bench to bring up the ridge, since casting tends to round the apex.

Use and durability

The knife-edge shank is most commonly paired with a single round, oval or cushion centre in a solitaire engagement ring. Its weak point is the apex itself, which is vulnerable to wear over time as the wearer's daily contact with the band gradually rounds the ridge. The original sharp profile usually requires restoration after five to ten years of regular wear, achieved by re-filing and re-polishing at the bench. Knife-edge shanks are not well-suited to channel-set or pave bands, since the narrow upper surface does not accommodate side stones, and are therefore reserved for designs in which the band itself is meant to read as plain and sculptural.