Hand-held drill with self-advancing bit

A hand-held drill having a controlled feed rate comprising:

• an outer case including a wall dividing said case into a motor compartment and a limiter compartment;
• a pneumatically powered drill motor having a housing slidably mounted within said motor compartment;
• air entry means in fluid communication with said motor compartment;
• trigger valve means associated with said air entry means and adapted for connection to a source of compressed air, said trigger valve means operable to provide a flow of air from said source to said air entry means;
• air guide means associated with said case and said drill motor housing for channeling said flow of air into said motor compartment and directing a first portion of said compressed air into said drill motor and a second portion of said compressed air directly against said drill motor housing to produce longitudinal movement of said housing within said casing;
• limiter means mounted within said limiter compartment attached to said housing to limit the speed of longitudinal movement of said housing, said limiter means including a piston axially aligned with said drill motor and slidably mounted within said limiter compartment and a connecting rod affixed at a first end to said piston extending through said wall and affixed at a second end to said housing, said limiter compartment containing hydraulic fluid, said piston having at least one bore formed therethrough to allow hydraulic fluid to pass through said piston, a flow limiter means mounted within said bore to limit the rate of flow of hydraulic fluid through said bore;
• a spindle axially aligned with said drill motor;
• and
• a coupler removably affixed at a first end to said spindle and at a second end to said drill motor, said coupler being cylindrical and including means for damping forces directed transversely to the axis of said coupler, said means including a reduced-diameter portion of said coupler between said first and second ends, said reduced-diameter portion being of a size to make said reduced-diameter portion sufficiently flexible to counteract any forces directed transversely to said coupler.