《天工开物·中篇·锤锻》
凿子是用熟铁锻造成的，是在刀口上嵌钢，凿身为圆形，中间留有孔洞，用来方便装进木柄。
凡凿熟铁锻成，嵌钢于口，其本空圆，以受木柄。
The chisel is made of wrought iron, with steel embedded in the blade, and the chisel body is circular, with a hole in the middle to make it convenient to fit into the wooden handle.