MAKING

AN

AUTOMATIC CENTER PUNCH

 

Actually, the term automatic is a misnomer, it still has to be lined up by hand. The difference between this and other punches is that it operates with a built in ram that slides up and down the shaft of the punch. The point of the punch is placed on the cross scribe lines of the work piece and held vertically while you raise the ram a few inches and the let it drop. The ram is not drilled all the way through so as it comes down it effectively hammers the top of the punch to gently and accurately make a punch mark. The term comes because it does not need a hammer. Make a round punch as we did earlier and put it aside. The punch needs to be about six inches long and the ram about four inches long and between 3/4" and 1" in diameter. Any heavy metal will do for this part. Chuck the ram and support the end with a steady rest. A steady rest is a contraption that attaches and can slide on the lathe bed and has three bronze bearings the are brought to bear around the circumference of the work piece. Oil is applied to the bearing points and the steady rest is slid as close to the unsupported edge as the work allows. Begin by taking a facing cut, center drill and drill a 3" hole with a drill bit the same diameter of the punch body. Reverse the ram and face the remaining face. The "Automatic" punch is now completed and is ready to be put to use. Take the point of the punch and place it on the mark. Insert the ram through the top of the punch and carefully let it drop so the ram bottoms out and bangs the top of the punch causing it to make a mark on the work piece.