near all automatic center punches use a very similar mechanism <link wikipedia>. most problems (failing to punch/weak) are caused by the striking surface on the intermediate pin becoming worn. jammed punches can usually be fixed by removing all the parts, and reassembling them. make sure to add oil at the end.
note! some use a left-hand thread for the top and bottom parts, and/or a large quantity of threadlocker. <make this an infobox>
unscrew the bottom piece that holds the punch into the hammer mechanism, as so:
there should be two parts that come free; the punch (can be left in the bottom cap), and the intermediate pin. remove it, taking care to keep track of any springs.
note that the pin is angled relative to its base (or should be, at least), and the attached spring is also angled.
pull the spring off (or don't, if it's too hard), and place the pin's surface on a file. file down the surface, making sure to preserve the angle of the pin (or add one, if the pin is *that* worn), until it is flat, and free of dimples or other marks. it doesn't need to be super smooth, but aim for relative smoothness. wipe off any metal dust.
before | after
when reinstalling, ensure the spring is rotated to maximize the angle that the shaft of the intermediate pin sits at relative to the top of the spring.
after other fixes:
scratchy action can be fixed by removing the upper cap and the spring atop the hammer, and adding some drops of machine oil (it should pool on top of the hammer).
reattach the cap, and cycle the punch five or so times. reinstall spring, and screw upper cap back on. this might be difficult, as the hammer's spring is rather powerful.