Flexshaft handpiece mount for workbench (rotatable, parametric)

Sometimes it is quite useful to have the flexshaft handpiece mounted in a fixed position on your jewellers' workbench. This will do just that with the added flexibility of being rotatable wround its Z-axis.
The handpiece holder is to be mounted on a piece of wood that can be held in the benchpin holder of the jewellers' workbench.
By default, you will need an M5x16mm (Allan key) screw and nut to hold the handpiece in place and a M6x40 hex-nut screw, washer and a wingnut to mount it on the wooden board that goes into the benchpin holder.
The design of the handpiece mount can be altered/adjusted to match your handpiece (the default is for a Foredom 3-jaw-chuck handpiece) and your preferred screw sizes.