Cordless drills come in 12-, 18-, 20-, and 24-volt models. Generally speaking, the higher a drill’s voltage, the greater the amount of speed and torque it produces, but there is a caveat here.

The Hitachi cordless drills, which retailed for $100 to $140, were sold from September to December 1996 at stores, lumber yards and in various tool catalogs. The 9.6-volt battery packs that ...