What type of metal blade. Bronze is too weak to do the job.
Limestone is nothing to cut or chisel away.
American indians drilled holes through everything from slate to tough conglomerate with river cane, which contains silica. Once you get started, the debris in the grooves acts as grit to improve the sped of the cutting. It’s how they prepared atlatl weights for hafting on atlatls, etc.
To saw conglomerate rather than drill it, one may just need grit to pour into the path of the swinging blade, which would not need to be any harder than bamboo.
The article notes that it isn’t limestone.
The blade is not the cutting agent. As with today’s glass slotted tube drills made from brass, there are slots that hold a cutting medium, sand. That medium along with water does the actual cutting.