Wood – How to drill a groove to the side of a plywood board

Yes, the drill chuck will mar the finish of the shelf. There is a slight chance of damage to the chuck. Plus, choking down on the bit, like that, obscures your view of the hole (the drill and chuck block it) -- making precision harder to accomplish.

The correct way to do this is to use a drill stop.

Drill stops are less likely to slip than tape or zip-ties, and are much better for precise and/or repeated drilling.

If marring the finish is an issue, clamp a piece of 1/8th plywood over the site and adjust the drill stop accordingly.

PS: A piece of wood over the hole is usually a good idea anyway, when drilling finished surfaces. It helps reduce both splintering and the scratching that occurs when flakes of drilled wood or metal whip around the bore site.

Think back to your high school physics class and use the Right Hand Rule.

Lay the drill bit across your palm, with the point towards your thumb. If the fingers curl around the bit (or screw) in the direction of the threads, then it's a right handed bit. That means you turn clockwise to drill (from the perspective of looking down on the work).

This rule is also extremely helpful when you are working upside down and backwards trying to tighten something. Point your right thumb in the direction you want the screw or nut to travel, and turn the object in the direction your fingers curl to tighten.

When in action, Clockwise/Forward looks like this.