Precision parts are difficult to assemble using only position control. To deal with this difficulty, force control approaches, which provide proper motion responses against contact forces, are investigated. Moreover, hole detection is a crucial step in eliminating the uncertainty in robotic assembly. Without a proper hole detection algorithm, assembly time increases with the position difference between the peg and the hole. In this study, we propose a shape recognition algorithm based on a 6-axis F/T sensor and a hole detection algorithm. The proposed hole detection algorithm can find the direction of a hole regardless of the size of the position error between the peg and the hole with some overlap of the hole and the peg. The same algorithm can be implemented not only for a circular peg, but also for a polygonal convex peg. A series of experimental results show that the proposed algorithms can estimate the shape and location of a peg reasonably well.