When to Replace Piano Hammers (vs. Voicing Them)

Piano hammers wear over time, and worn hammers cause harsh, bright, metallic tone. Two solutions exist: voicing (reshaping or treating the felt) or replacement (fitting new hammer sets). Voicing costs S$120–S$350. Replacement costs S$600–S$1,200. The right choice depends on how worn the hammers are. Here is how to tell which is needed.

How Piano Hammers Wear

Each piano hammer is a felt-covered wooden block. The felt is compressed wool — dense and resilient when new. Every keystroke drives the hammer against the strings, compressing the felt contact area. Over thousands of strikes, the contact area (which should be a small convex crown) flattens into grooves — one groove per unison string (two in the middle register, three in the treble). Grooved hammers produce bright, metallic tone because the flat surface makes full contact with the string simultaneously rather than a progressive contact. Hardened felt in the grooves compounds this effect.

Voicing — What It Is and When It Works

Voicing is the process of adjusting hammer felt density by needling or treating. A piano technician uses a voicing needle — a thin spike — to pierce the felt and break some of the compressed fibres. This loosens the felt, allowing it to deform during string contact and produce a rounder, warmer tone. The grooves can also be reshaped with fine abrasive tools to restore crown shape.

Voicing works well when:

• The hammers are moderately worn — visible grooves but felt thickness is still adequate
• The hardening is at the surface, not through the full depth of the felt
• The tone is harsh but not metallic and clangourous
• The piano is a home instrument used for practice, not a performing piano

Voicing cost: S$120–S$350 for a full set. Result lasts 2–5 years depending on usage.

When Hammers Must Be Replaced

Hammers need replacement when:

• The felt is worn through — the grooves are so deep that the felt crown is exhausted (if you look at the hammer from the front, the grooves are nearly touching)
• The felt has hardened through its full depth (needling has no further effect)
• A hammer or shank is broken and the set is old enough that replacement of the whole set makes more sense than matching one hammer
• The piano is being used for performance or teaching and requires consistent, controllable tone quality

Replacement cost: S$600–S$1,200 for a full 88-hammer set including fitting, regulation, and initial voicing. Different hammer grades (Abel, Renner, Yamaha-specification) are available at different price points.

What Happens After Hammer Replacement

New hammers require fitting to the action (alignment with strings), break-in (initial voicing to control brightness from factory-hard felt), followed by full regulation of the action to accommodate the new hammer geometry. The process takes one to two visits. After break-in, the piano tone stabilises and can be refined further with voicing visits over the following months.