Abstract: A keyseat wiper or reamer for enlarging keyseats which are often formed in drilling bores during well drilling operations. The wiper comprises a generally cylindrical body including a cylindrical middle guard portion which has a greater cross-sectional diameter than the greatest diameter of the cutting elements of the tool, the middle portion being free of any cutting elements. Cutting elements extend in a tapered manner from the middle portion to opposed locations toward the ends of the wiper. Because the middle guard portion does not carry cutting elements and is the largest diameter portion of the keyseat wiper, the keyseat wiper will cut only when the hole through which it is passing is of diameter smaller than that of the middle guard portion or when the well bore has a curve or dogleg.