DRILLING FLAT SIDED HOLES

摘要

The traditional way of making a square hole in the home workshop has been to drill it round first and then open up the round hole to the required square by filing. Filing accurately is a skill only obtained by years of practice and I don't have the necessary long years ahead of me to devote to filing practice. Hexagonal holes require even more skill. Filing is all very well if there is somewhere for the end of the file to go but for blind holes it is almost a non starter. Commercially, through holes might well be broached, a process which we may think of simplistically as an extension of filing, while blind holes or those progressing to a smaller hole, may be forged or punched. Typical examples would include sockets in Allen screw heads, and the squares and twelve point holes in socket sets. For use by the amateur, I propose to describe two methods. Long square holes can be drilled by the first method and the second will take care of blind holes.