Frankly, for very hard wood I would not recommend full-chisel cutters.
I am also waiting to see the pictures, but based on what the Australian guys say when cutting their hardwoods, I would be suggesting semi-chisel cutters, filed at 25°, with limited ‘hook’, as a starting point.
The STIHL 2-in-1 can be positioned at 25° (mark the new angle with a protractor and tape), but may take down the depth gauges too far.
On a grinder I would start at 25° / 60° / 0°. More acute cutting edges will not hold up as well.
Philbert
I am also waiting to see the pictures, but based on what the Australian guys say when cutting their hardwoods, I would be suggesting semi-chisel cutters, filed at 25°, with limited ‘hook’, as a starting point.
The STIHL 2-in-1 can be positioned at 25° (mark the new angle with a protractor and tape), but may take down the depth gauges too far.
On a grinder I would start at 25° / 60° / 0°. More acute cutting edges will not hold up as well.
Philbert