Microfinishing Film – the hands down very best filing material for piano hammers. This is an industrial abrasive with some very interesting characteristics and applications for us piano technicians. The backing material is a fairly stiff and very durable mylar film. It has the advantage that it will only bend in one plane at a time. This helps to maintain flat filing surfaces and crisp and defined edges on hammers. It will not stretch and will never tear.
The grit itself is aluminum oxide – a sharp and durable abrasive. The grains are micro-sorted by size to a high degree of precision; this results in an aggressive cut, yet a smooth finish. The Microfinishing film is denoted by the grain size in microns e.g. 100µ, 60µ etc. This material comes in 100µ, 60µ, 40µ, and 15µ which corresponds to 100, 200, 320 and 600 grit for fine polishing the striking surface.
This material’s amazing performance and durability makes it the abrasive of choice for hammer shaping. It is ultimately very cheap to use, costing only pennies per set of hammers filed. This material will outlast any sandpaper; one university technician recently reported having filed almost 1000 (!) sets of hammers over five years years with one set of strips which were still going strong.
The Microfinishing Film is sold in the Hammer Filing Kit, consisting of four 2″ strips of different grits plus one Plexiglass file for mating hammers to individual strings as shown in André Oorebeek’s book “The Voice of the Piano”.
- # 130315 Microfinishing Film Filing Kit