A Simple Countersink Tool
By Daniel Burgoyne
I was working on a small project this weekend using M3 flat head screws, pulled from spares of a European radio-controlled racing car with the intent of keeping costs to a minimum and completing the project before Monday. Unfortunately, I did not plan my project ahead and did not have a 90° countersink tool in my toolbox (a standard, imperial size 82° countersink is not really adequate for metric screws). Buying a new countersink tool from my local supplier was going to take money out of my pocket and put off the completion of the project beyond the weekend – neither of which matched my "project criteria."
Instead, I dug up a cheap 1/4" HSS drill bit ($1) from my "might use this one day" inventory and sharpened it freehand on the grinder to a 90° inclusive angle, using a protractor set at a 45° angle to verify point symmetry.
I chucked the bit in the drill press and chamfered all the holes in the mild steel, without chatter and to the correct head diameter for the M3 flat head screws. As an added bonus, the jobber's length drill bit used in this case is longer than regular countersink tools and that meant not having to change the setup on the drill press table after drilling the holes.