The automatic center punch is a device used to make a pinpoint identification in a hard material such as metal or plastic.It perform the same function like an ordinary center punch but without the used of the hammer. When pressed against the workpiece, it stores energy in a spring eventually releasing it as an impulse, the drive punch producing a dimple. The identation provides a more stable staryting point for a drill to cut the material. It is used for a wide variety of other applications these include ; letter stamps set, glass breaking tools, pin press for electronic assemble and other. The automatic center punch resembles a short screw driver but instead of a having a tip like a screw driver, it has a round shaft shortened to a conical point. It is made up of six basic parts such as the handle hammer mass, intermediate rod, return spring and the point.
The handle is containing a driver assembly which consist of a very stiff spring and a releasing hammer which resembles that of a screwdriver is approximately 1 1/2 inches in length and 13/16 inch in diameter. The handles plastic exterior permanently encases a stiff spring and a releasing member. The spring is the part that drives the point to the material.
The hammer mass is a spring loaded from the back of the punch by a large spring. The spring's preloaded compression can be adjusted by loosening or tightening the end cap at the back most portion of the punch. A stopped hole drilled in the front center portion of the hammer mass facing intermediate rod acts as a receiver for the rod and as an anvil for the punch action.
The intermediate rod which provides the automation, when preset, a provision is made such that the rods is cocked slightly so that it is resting position is skewed and tip contacts the hammer mass, This is commonly done by using special bent end on the intermediate pin spring or using an out-of flat face or bottom end of the pin or top of the punch. It bears of the hammer mass and pushes it back against its spring. The punch is pressed storing energy in the hammer spring. The punch is further pressed against the workpiece, the intermediate rod travels back until a certain point where its mid-section begins contracting surface and as it continues back becomes aligned toward the center axis.
The return spring is a steel spring not much different from the type used in most ballpoint pins. It returns the points to its normal position after the tool has been used.
The retainer is a tubular piece of steel which contains the return spring and the point. Its inside diameter is 17/64 inch at its wide end and 5/32 inch at its narrow end. The retainer is 43/64 inch from end to end and has 32 threads per inch at its wide end,which screws into the based of the handle.
The point is the steel bar 1 5/16 inches long which is machined and polish to a main diameter of 0.1532 inch. The end opposite the point measured 0.0923 inch in diameter for a distance of 3/8 inch. Twenty-five thirty seconds of an inch from this same end, a groove is cut completely around the shaft. A separate piece of wire wraps around this groove to old back the return spring. The pointed end of this shaft is sharpened to a 60- degree angle and hardened to resist wear.
