General Tools & Instruments 79 Steel Automatic Center Punch
Use automatic center punches to precisely punch material for drilling and layout work.  Spring operated tool drives hard point in a single one-handed operation that eliminates striking a punch with a hammer. Spring tension cap can be adjusted for light to heavy strokes. Punch depth can be set for repetitive work. This is a steel automatic center punch for making lighter markings than #78.  It has a black oxide finish that inhibits rust.  The all-steel body is 5" with threaded, replaceable hardened steel point and shaft.  The body diameter is 1/2".