Maintenance Views: 11

Countersinks can be hand re-sharpened, but it is not recommended: 1) Angle accuracy is hard to hold - errors over 1 degree are common, causing uneven chamfers and unseated screw heads; 2) Edges come out less sharp - hand-ground edges often have burrs and unevenness, hurting surface finish; 3) Poor symmetry - multi-flute tools ground by hand rarely stay symmetric, causing runout and vibration; 4) Slow - hand grinding takes ten-plus minutes per tool versus minutes on a machine grinder. If you must hand-grind: 1) Use a tool grinder or precision sharpening machine, not a plain bench grinder; 2) Check the angle with an angle gauge or template, keeping error within +/-0.5 degrees; 3) Keep edges sharp - finish with a light pass of an oilstone to remove burrs; 4) Keep multi-flute edges symmetric and even; 5) Remove only the worn portion each time; 6) Check runout after grinding, re-clamp or re-grind if high. Recommendation: send valuable, high-precision tools to professional sharpening; hand-grind only cheap, low-tolerance tools. Cobalt HSS countersinks can normally be re-sharpened 3-5 times, performing almost like new afterward.