The USPTO system of classification of patents is difficult to understand.Although there is, within the system, a class for "TOOLS" (Class 81). This class has several subclasses which include the term "screwdriver;" yet the system places sprial screwdrivers in Class 74, Subclass 127. Class 74 is defined as "MACHINE ELEMENT OR MECHANISM" and Subclass 127 as "Screw and nut devices."
Here are some of the classifications which the USPTO assigns to screwdrivers:
SCREWDRIVER ......................... 81/436+ 436 Having work engaging and force exerting portion inserted into cavity (e.g., allen wrench, screwdriver)
COMBINED WITH DIVERSE TOOLS .......................7/165+ 7 Jewel setters'
COMBINED WITH DIVERSE WRENCH ....................81/437
CONSTRUCTED FROM SPECIFIC MATERIAL........ 81/900*
DESIGN ....................................................................D08/82
FLOOR JACK ............................................................254/13
EYE SCREW, ADAPTED FOR ..................................81/901*
MACHINE ..................................................................81/54
Source: PTO Manual of Classification for US patents