Step drill, 3-12mm

Two-step reamers are best if you often need to ream out for endpin strapjacks. However, for occasional use a cheaper option will often do, as you just need a neat 12mm (1/2") diameter hole. This step drill (also called a pagoda drill) is a reliable alternative, made from high quality high speed steel, with a titanium coating to reduce friction and heat. It can be chucked in an electric drill and then run slowly to produce a very clean hole. On a mandolin or archtop guitar it will also cut through the tailpiece with no trouble. (You can leave the tailpiece in place when drilling, meaning that the hole through the tailpiece and the endblock are exactly aligned. ) As well as allowing you to open out the hole gradually, it has a long enough shank to allow you to make a 12mm hole through the full thickness of the endblock on most guitars (though it does depend on the drill chuck as well).