This is the best countersink bit set if you want to simple cross holes. The CRL Weldon Countersink set has an 82 cutting angle and is ideally used for aluminum material. Its best suited for a 1/4 ...

Almost all countersink bits are made from high-speed steel (HSS). However, quality bits will be made from HSS that has an enhanced development process, such as M2 HSS or heat-treated HSS.

Combination countersink bits come in various screw sizes (typically 4, 6, 8, and 10) and are sold individually or in sets.