Drill bit sizes

Abstract: The accuracy of drill hole location is critical for implant placement in orthopaedic surgery. Increasing drill bit size sequentially has been suggested as a method for improving the accuracy of drill hole start location. The aim of this study was to determine whether sequential drilling or drill angulation would alter accuracy of drill hole start location. Three specialist veterinary surgeons drilled holes in synthetic bone models either directly, or with sequentially increasing drill bit sizes. Drilling was performed at 0o, 10o and 20o to perpendicular to the bone models. Three synthetic bone models were used to mimic canine cancellous and cortical bones. Sequential drilling resulted in greater inaccuracy in drill hole location when assessing all drilling angles together. There was no influence of surgeon or synthetic bone density on drilling accuracy. The combination of drill angulation and sequential drilling increased inaccuracy in drill hole start location. We conclude that sequential drilling decreased accuracy of drill hole location in the synthetic bone model when drilling was angled. Inaccuracy associated with the drill hole start location should be taken into account when performing surgery, although the magnitude of inaccuracy is low when compared with other sources of error such as angulation.

Abstract: A tool holder assembly is for use with a hammer drill, and the assembly has two adapters of which the first is capable of accepting drill bits having a bit diameter of between 5-17 mm and a drill crown is provided having an inner and outer cone to accommodate the shaft of the drill bit The drill crown fits on the outer core and is capable of accommodating drill bits larger than 17 mm diameter having an internal cone (9) only Both holders have the same hexagonal fitting for attachment to the chuck end of the tool spindle

Abstract: A drill hole repositioning tool has a handle or a head for holding the tool, and an elongate drill bit guide having a crescent-like cross-section. The elongate drill bit guide is inserted in an existing drill hole with the convex side of the elongate drill bit guide butting on a side of the existing drill hole. The concave side of the drill bit guide guides a drill bit for drilling a new drill hole. The new drill hole is displaced from the existing drill hole by the thickness of the elongate drill bit guide. A set of drill hole repositioning tools may have a range of thicknesses of the drill bit guides to cater for a range of drill hole repositioning displacements, a range of diameters to cater for a range of standardized drill bit sizes, and a range of insertion lengths to cater for a range of drill hole depths.

Abstract: A hand-held block holds drill bits in position when using a hand-held drill. It preferably contains six holes of the most common drill bit sizes. The block is held by the user who inserts the drill bit into the appropriate hole in the position the user wishes to drill into the surface. The block may be divided into six sections, one for each hole, for individual use if the workspace is limited (see figure 2). A spirit level may be incorporated into the block to facilitate level drilling of holes. Preferably the block is provided with a rubber backing.