grand piano (ascr. Franz Jacob Späth ca. 1770) Detail: key fronts

P.1: 

Späth grand original, keyboard with bright upper (bone) and dark lower keys (top covers ebony,  front blackened pear).

evidence: key fronts blackened pear (evident by visual examination under the microscope).

P. 2: Späth grand original, detail key fronts.

production hypothesis: profiles of the key fronts scraped/cut in circular movement with a turning tool.  plates in full circle profiles subsequently halved.

P. 3: 

Making a matching turning tool by filing a matching profile into a card scraper.

P. 4: 

Initial material are honed pear boards honed (to 2 mms strength) and cut in length and width to approx. final dimensions. A specific  four-jaw chuck is required. First step is the centering to assist the follwing centering of the grooved tool for scraping.