Creating a small divot on your metal before drilling a hole makes the task much easier. The indentation prevents your drill bit from dancing around the surface of your piece, causing unsightly scratches. Traditionally, this task is done with a hammer and a pointed steel tool, called a center punch.
This important detail can get rather tedious when there are numerous holes to drill. If you are working on a curved surface, holding the piece, the center punch and the chasing hammer can feel like a juggling act. An automatic center punch makes the job much easier, freeing up one of your hands to hold the piece more directly. The automatic version is spring loaded, requiring you to only press firmly down where you need to create an indentation. These are available from jeweler supply companies ranging in price between $14 and $25.
However, you can get one from Harbor Freight for just a few bucks. The regular price is about $5, but they are often on sale for around $3. Check out their website for the current price. http://www.harborfreight.com/spring-loaded-center-punch-621.html This model packs a pretty strong punch, intended for use with harder, heavier metals than what most jewelers typically use. Fortunately, they are easily altered with a few tools most metalsmiths or jewelers already own!
This quick project requires sand paper or a brown silicone wheel, a piece of scrap metal, a separating disc and a flex shaft or some other rotary tool like a Dremel.
Before beginning, test the punch on your scrap metal. Chose a piece of scrap that is a similar material and gauge to what you typically like to work with. This will help you optimize your center punch. To use your punch, you simply need to press straight down. You will hear the spring pop, and feel the punch release tension. It may be difficult to fully depress the tool before you begin alterations. The goals are to make small indentations and to make the center punch comfortable to use.
To begin, unscrew the top of your center punch and take out the spring. Using your separating disc, cut off one complete coil. Reassemble the center punch and test on your scrap metal. If the tool still seems too forceful, take it apart and cut off about half of a coil. This is a back and forth process until the pressure feels right to the person using the center punch. Cutting off three complete coils is probably the maximum you can remove and still achieve good function. You may hear the spring rattle a little inside the punch. This will go away with time as the coil relaxes a bit.
For the finishing touch, I like to smooth out the point just slightly. I use a brown silicone wheel to make a quick job of it, but sand paper will work also.
Once you have you spring cut and your tip smooth, you are ready to start punching!