Center punched are great when they are sharp and pointy. That's what makes them accurate. Over time and used on harder materials they will dull and become less precise, but you can fix that. You can simply sharpen by hand, but here's a little trick, use a hand drill to spin em, that will give you a nice and even point. Now this next part is key. Grinding the tip heats up the metal, which aneils or softens the metal so as soon as you are done grinding your tip you need to quench it quickly. Just