Until now, there was no precise tool to measure the horizontal drilling angle of hammers in relation to the strings. We developed a a protractor that offers maximum precision and is extremely easy to use. It is compatible with all types of hammers, whether for upright or grand pianos. 
 
The adjustable hammer head helps measure the exact angle between the hammer shank and the strings. It screws onto a new shank in place of the hammer head. The upper part is adjustable, and once installed in the piano, you are supposed to ajust it to face the strings.
 
The rake angle protractor helps measure the vertical angle between the shank and the hammer head. Start by drawing a line on your hammer. Then place the tool on the shank, on either side, and align the edge of the tool (or the groove, depending on the version of the tool you have) with the line. You can then read the value, typically 90° or 91°.
 
Download the User Manual in English. 
 
(Hammer-head, shank and flange not included...)