Countersinking With a Spade Bit
A short piece of rod welded to a spade drill bit keeps the bit centered in the hole.
The most annoying thing about using a spade bit to enlarge an angled hole for countersinking is keeping the bit centered in the existing pilot hole. To make this easy, I cut off the pointed end of a 1-1/2-in. spade bit, and welded on a short piece of 1/2-in. rod in its place. Now when I put the drill bit into the previously drilled pilot hole, the bit stays centered.
—Gerret Wikoff, Los Angeles
Edited and Illustrated by Charles Miller
From Fine Homebuilding #294