Facom 90 Degree Cone Bit for Countersinking -10mm Cone width (229.TT2) - drill a pilot hole and follow with the appropriate sized countersink bit. Based on the Spax screws I sell, the 10mm (.394") countersink bit is the correct size for #6, #8 and #10 screws (good for screws up to 3/8" in size). These Facom bits have 3 HSS cutting edges for clean countersunk holes. HSS (High speed steel) bits are more resistant to heat than carbon bits.

For use with wood or metal. See photos (click to enlarge) for sizes and dimensions of the 4 different bits. Also available as a 4pc set with lubricant and case....see 229.TTJ4 .