A common way to get a drill to start at a specific location is to first use a spring-loaded punch to make a small divot. This holds the point of the drill in place until it can start cutting. If you have more than one hole to make, switching between drill and punch can get tedious.
Here is an alternate approach that can be fabricated in seconds. It handles a range of dome sizes and also works on the ends of rods.
If you are interested, please see
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