An online measurement system for the deep hole machining force of quartz prefabricated rods has been designed and implemented， addressing the unique characteristics of the rods' mounting structure and the critical relationship between cutting force and tool wear. Leveraging the drilling process dominated by axial force， a double-guide design was employed to isolate the tilting moment and other directional forces， enabling low-cost， real-time cutting force measurement through a unidirectional piezoelectric force sensor. To validate the system's effectiveness， multiple experiments were conducted on quartz prefabricated rods using tools exhibiting varying degrees of wear， and the correlation between cutting force and tool wear progression was analyzed. Experimental results on Panda bias-preserving fiber prefabricated rods indicate that the core is susceptible to fracture when machined with a 12.8 mm diameter tool at cutting forces approaching 150 N.