Recently I was building some folding chairs from pecan and needed to recess the square shoulders of carriage bolts into the wood. Pecan is too hard to just draw the bolt into the wood by tightening.
Instead, I drilled the bolt hole first and inserted a short piece of matching dowel with a chamfered top end. Then, I fitted a hollow mortising-machine chisel over the dowel, which acted like a centering pin.
I tapped the chisel into the wood with a dead-blow mallet and pulled out the dowel to create a perfectly centered square hole for the bolt.
– George S. Setta