I'm making a knife using a sgian dubh blank as a starting point - something like this: https://www.thesheffieldcutleryshop.co.uk/shop/new-fantastic-sgian-dubh-carbon-steel-blank-blade-made-in-sheffield-england/
However I'm having some issue with broaching my handle (oak) for the tang. The thickness of the tang is 2mm, and it is ~40mm long. I have tried drilling out with 2mm long series drills, but they tend to wander and it's near impossible to chisel out the remainder of the wood to clean up the hole. I've been using an old jigsaw blade as a broach, and also made up a miniature motice chisel. But trying to work down a 2mm wide 30mm+ deep hole is a challenge and I haven't been able to clean it up to full depth. Considering doing a bolster instead so I can use a larger drill bit. Has anyone worked with these before? Wondering if anyone has any tips for making this sort of hole?