Twist Bits & D Bits

I need to know the best way to drill a straight bore through African Blackwood, or any other material. I tried today using a 1/8” x 12” twist bit to do the task. It worked but only went straight for the first ±5” only to come out the other side about 1/16” from the edge.

Seth Hamon: “You can make a start hole with a twist bit, then follow with a d bit. Twist bits will follow a pilot hole to a point.”

So I am wondering how accurate the twist bit will be after drilling the pilot hole with a D-bit, or does it go so far and turn course no matter what you do? Also, need to know how to make D-bits?

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If you have a good pilot hole, the twist drill (for expanding the bore) will be accurate enough for my purposes, which means there can be a runout of maybe 1/32" over a length of 16", provided you work carefully and slowly.
However, up to a bore diameter of 1/2", I prefer to widen the bore using bigger D-Bits.

By runout do you mean a 1/32" off when it comes out the other side? Seems to me if that where the case if there is still substantial amount of wood left you could turn in once more and true it up. This would then give it a strait bore.