The G81 code word is for the standard drilling cycle

Example G81 X1. Y1. Z-.2 R.1 F3 G99

This cycle can be used for center drilling, drilling, reaming, and rough boring. The cycle rapids to R-plane, feeds down to the Z-depth at the set feed rate and then rapids out of the hole.

Notice that the depth is somewhat shallow. For drilling deeper holes, another cycle is recommended, such as G73 or G83. Chips can clog in the flutes and break or overheat a drill.