How to make a piano keyboard

Step 7 Marking up the keyplank

I drilled and cut the keyboard manually so I had to mark different details on it.

I used the marking gauge to scribe lines on the top of the keyplank corresponding to the back of the wide portion of the white keys, usually about 4.5cm from the front, and another line about 3mm behind it corresponding to the front of the black keys. I scribed similar lines on the bottom but offset from the top one making about a 10° downward angle toward the front for the wide part of the natural keys which reduces some weight and makes clearance for the raised keys. Sometimes the raised keys are cut with a smaller angle toward the back.

I adjusted the gauge to about the middle between the front of the keyplank and first bottom line, and scribed this across the top, and then scribed a second line about 1cm behind the front of the black keys. These lines correspond to the two rows of holes for the front pins. It can also be helpful to make lines on the bottom about 5mm to either side of them to show the limit of the mortises, especially if the mortises are going to be bushed so that the wood between them can be planed cleanly down by about the thickness of the cloth.

I trimmed the keyplank to its final width, with table saw for the parallel sides at the front and bandsaw for the angled sides at the back as well as the front, and then marked out the divisions for the individual keys. First I marked the heads, or the wide front parts of the natural keys, making even spaces up to the first line on the top of the key, and up to about the back of the raised keys between every E and F, and B and C keys.

To find the divisions for the back of the natural keys and for the raised keys Blüthner, Wolfenden and writer on pianos Lawrence Nalder all described dividing the space occupied by C, D, and E, into five equal spaces, and F, G, A, and B, into seven, but Wolfenden points out this can make it hard to play between F# and G#, and G# and A#. The two different spacings make the rear portions of the C and F keys wider than the neighboring B and E keys, though this can be remedied by sawing to the side of the line instead of in the middle, and requires two sizes of sharps, which can be adressed in the same way. Architect and writer on organs George Audsley suggested to subtract the width required for equal sized sharps before dividing into three and four spaces respectively, which results in an even greater difference between the neighboring tails, and Wolfenden suggested alternatively that the Cs, Ds, and Es be made slightly wider than the Fs, Gs, As and Bs, with uniformly narrow sharps.

Each writer advised making a wooden pattern from the divided keyboard to save the effort of dividing it again. Blüthner suggested drilling holes through a wooden pattern so their positions can be transferred with a punch, and Audsley described that in the key making department at the Steinway factory they used patterns with embedded points so that all the marks would be made at once.

I already had a pattern to work from that I used to mark the divisions in the front. I glued the pattern for the divisions at the back of the keys to a piece of thin plywood and punched holes for both sides as well as the middle of each key. The balance pins fall in two rows so the leverage of all the keys is the same, and I scribed lines on the top of the keys set back a little from where they set in the rail because having the pins angled back makes the keys easier to put on and take off.

I lightly pencilled lines connecting the marks for the sides of the keys at the front and back, and punched marks for the balance pins centered between the pencil marks, along the corresponding scribed line. Technically their most efficient position falls in line between the where the key is pressed and where it works the action, but it's also important that they are centered on each key and aren't surrounded with short grain. When there's a large sideways offset between these it's common to make multiple angles so that the portion around the balance pin is parallel with the front and the back parts, in a shape sort of like a dog's back leg, to have more wood and stiffer straight grain at the fulcrum.