The process is put together from different pianos. And there must be some better ways to do this.
Remove screws on pinblock, drill out dowels with spade drill bit. This type of drill bits are pointy, won't slide everywhere.
Mark a line on both bass and treble, 3 inches away from case. This will be where we'll saw. Put a mirror on keybed, get a reading on stretcher thickness with a combo square, set it about 2mm over the actual thickness.
Set the router bit to match the stretcher thickness including the 2mm room so we won't cut into the stretcher. Route from under the stretcher. Safety classes shall be put on very tightly. Saw dust shoots everywhere.
Use sawzall to cut at the 3 inch mark on two ends. Hammer the pinblock off.
Chisel the rest of block off layer by layer. The shop owner uses power plane to remove the remainder thin layer of pinblock. To be safer, use a wet rag plus hot water or steam to soften glue, then chisel off the remaining thin layer.