Combination pneumatic hammer, spring and guide for chisels in use for sealing Pittsburgh lock seams

A spring and guide combination for a conventional pneumatic hammer and chisel of the type in which the pneumatic hammer has a stepped barrel including a round base portion and a reduced-down distal portion externally formed with inverse spring thread, and in which the chisel has a shank terminating in a butt end which reciprocates between extension and retraction in the hammer barrel as well as having an intermediate axial-stop means;

• wherein, said combination for folding sheet metal edges comprises:
• a chisel-retaining spring having a main body formed on a given diameter, a shank-latching portion, and a transition section intermediate therebetween;
• the main body comprising a series of closed regular coils which partly thread onto the inverse spring thread of hammer barrel and in other part, with inclusion of the transition section, generally project so that the chisel-latching portion latches across the shank of the retracted chisel forward of the axial stop, whereby axial extensions of the spring normally retract the chisel back into the hammer barrel;
• and,
• a guide having a base end formed with clamping means for clamping onto the hammer barrel base portion, and at the other end, a guide lip to prop and/or slide against a wall of sheet metal and also act as a fulcrum and hence allow a user to vary the angle-of-attack of the chisel relative to the work-piece/sheet metal edge;
• the guide including an intermediary channel portion which internally closely surrounds portions of the spring for buttressing the transition section of the spring, and those coils of the main body proximate thereto, from off-axis excursions and thereby prevent against the latching portion of the spring from unlatching off the chisel shank.