The UJK Parf guide system relies on the fine tolerance of the fit between the dog holes and the dogs, neither too tight or too loose. Changes in humidity can cause difficulties in inserting or removing bench dogs. This stainless steel UJK Combined Chamfer and Reamer tool does two jobs at once. It has a 10mm hexagonal shank for a secure grip in a cordless drill chuck (1,400 - 1,700rpm). The Reamer portion has a gentle lead in and four cutting flutes to ream the holes to a precise size. Your bench dogs will fit snugly without wobble yet still enable you to remove them without difficulty. After the Reamer the Chamfer comes into action, cutting a neat, shallow chamfer around the top of the dog hole. This chamfer allows full use of UJK super dog and Parf anchor dogs etc. In addition, by removing the sharp edge around the hole, it prevents damage from repeated insertion of dogs, clamps and other accessories. The Chamfer features a solid tungsten carbide cutter. The UJK Chamfer & Reamer Tool is designed to slightly open up the 20mm holes to a size that will also allow for future movement or shrinkage due to ambient moisture & temperature change. Dogs fitted into these reamed & chamfered holes will feel very slightly looser but should still sit vertical due to the chamfer without movement that will affect squareness of cuts. Note: the Chamfer works best in MDF, HDF or ply with a melamine facing. Unfaced plywood may experience some slight tearout. NB: For use with portable drills only.