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No Tear Countersink in Woods, Even Soft Wood Like Pine
I often make wood projects using the old reliable "glue and screw" assembly technique. And, being thrifty, I often use inexpensive woods, like pine, which are not the best for working with. Drilling holes in soft wood with standard, twist drills will almost always produce produce tear-out on the edges of the holes. A countersink cutter will leave a somewhat better edge, but tear-out is still a problem and this will ruin the appearance of a project.
Some time ago I purchases an excellent set of brad point drills from Lee Valley and supplemented it with some individual sizes from Grizzly. These are great for drilling holes in wood, even soft wood, without any tear-out on the edges. They are so well sharpened that there really is no problem.
But what about a countersink? Here is what I worked out for making countersinks in woods with perfect edges - no tear-out.
1. Drill a small pilot hole, usually 1/16". There is no brad point drill that small in the set so I either use a size or two larger or just use a standard, twist drill bit. The tear-out will be small enough to ignore.
2. Then I choose a brad point bit that is the size of my screw head or slightly larger and just kiss the surface of the wood with it to score a circle. This prevents the tear-out.
3. I use a standard bit (resharpened to 82/90 degrees if the wood is hard) to hollow out the countersink. I find that the depth stop on one of my drill presses is good for doing this to a uniform depth. In the photo I was using a dry wall style screw which has a rather flat underside so I just used a standard bit with a 118 degree tip.
4. The final step is to drill the body sized hole, again with a brad point bit. When possible, this can be started from the bottom side of the piece to prevent tear-out even there.
The result is a perfect, countersunk hole in the wood. This photo was taken immediately after drilling: no sanding was done or needed.
