This project to convert an 8 bass Hohner Preciosa to 12 bass by uniting the treble side of a Hohner Preciosa with the bass side from a Hohner Regina piano accordion.  here are the two boxes at the start of the project.

The Hohner Preciosa and Hohner Regina

Fortunately the bellows are identical so its very quick to do this:

Preciosa treble joined to Regina 12 bass

But that’s not quite all there is to do.   The arrangement of the bass buttons has to be completely changed.  The buttons are to altered to a retabgular grid, instead of the skewed pattern at present.  The function of the buttons also has to be changed from a stradella system, to a custom melodeon system.  This will require modifications to the reeds, and to the mechanism that connects the buttons to the reeds.

First task is to make a new button panel to replace the one with skewed button layout.  Removing the old panel is nice and easy because it is glued in with that wonderful substance: hide/scotch/animal glue.  It softems in water so just apply some water to the joints, leave for half an hour, scraping off the surface glue after a while and eventually it comes out without damage.

soaking the glue prior to removing button board.

glue released

Now to prepare the replacement.  A suitable piece of plywood which should be less prone to distort than the original, and some white pearloid that is not quite an exact match, but pretty close.

replacement material

To glue these together I simply flood the surface of the wood with acetone, place the pearloid sheet on top, and clamp for a couple of hours in this wonderful nipping press.

Nipping press

Then with a bit of measuring and four cuts on the saw we have the new board ready to mark out and drill.