Steingraeber & Söhne KG

Steingraeber-Ferro-Magnet-(SFM) action®

Grand piano touch in upright piano models 130 and 138


SFM ® (DGM 202011001773.7) means grand-piano-like, deep repetition for professionals and is available on models 130 and 138. Four years of research and development and continous improvements resulted in a new product which offers the ergonomic qualities of grand piano mechanisms in upright pianos.

1Three specialties characterize the SFM-action®:

1) Magnet #1 underneath the hammer-butt leather.

2) Magnet #2, located at the tip of the jack, is activated by magnet #1.

3) No jack springs were used.

All parts are produced by Renner in Gärtringen.






A Summary of the Design Process

  • 2003-2004: Steingraeber tests began, using special parts in  Renner mechanisms.
  • 2005: The first prototype was presented in a Stein-graeber 130. This Dotzek-Ferro-Magnet-(DFM)-action was equipped with two magnets, a backstop-wire and -lead. Both types of springs, hammer-butt and jack, were dispensed with. 
  • 2006: The DFM was developed into the Dotzek-Schäffler-Ferro-Magnet-(DFM)-action by Wolf-gang Schäffler (Steingraeber's  production manager). Performance was optimized, and undesirable side-effects like "double strikes" were eliminated. Since October 2006, piano master builder Schäffler has collaborated on further refinements with Renner's head of operations, Günter Kolb.
  • 2007, September: Renner delivered the first, completed SFM parts ("Steingraeber-Ferro-Magnets"), all features were tested and optimized. In  anticipation of future EU lead regulations, lead free balance hammers were used.


1Two magnets in the hammer butt and in the tip of the jack activate each other. Thus, no jack spring is needed.

1Wolfgang Schäffler (left) was instrumental in the development of SFM. He is with the Company Steingraeber for more than 40 years now.

Sehen Sie hier die SFM-Mechanik in Aktion, in einem Video unseres Zulieferers GMB Deutsche Magnetwerke:




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