Hole punch apparatus

Hole punch apparatus comprising:

• first and second cooperating dies respectively mountable on opposite sides of a workpiece, said first die and workpiece each being formed with an aperture therein,
• a housing engageable with said first die,
• a shaft supported within said housing, insertable through said apertures, and engageable with said second die,
• a worm wheel threaded on said shaft,
• a worm engageable with said worm wheel,
• drive means including a power drill and means coupling said drill and said worm, whereby, when said drive means is actuated, said second die is drawn against said workpiece, compressing said workpiece between said first and second dies, and said first and second dies cooperate to punch a hole in said workpiece,
• said coupling means comprising a first portion rotatable by said drill, a second portion rotatable with said worm, and shearable means cooperating with said first and second portions for normally constraining them to rotate together but shearing in case of overload to permit said first portion to be rotated by said drill while said second portion remains stationary, and
• said first and second portions being concentric, said first portion surrounding said second portion, and said second portion being formed with means comprising a pair of flats respectively formed on opposite sides thereof for facilitating engagement by a hand tool, whereby, when said shearable means shears, a hand tool can be employed to turn said worm in reverse and disengage said apparatus from said workpiece.