For many of us, woodworking starts to become “real” when we pick up the drill. Pencil lines can be erased; dry-fitted joints can be swapped; boards can be rotated for a different view. A hole is different. The moment a hole is drilled, a piece of wood is changed, and this is why pilot holes must get a slower going-over than new woodworkers usually think they deserve.
A pilot hole is a small hole drilled through a board for a screw to travel into with reduced pressure. It reduces the likelihood of the wood splitting, can better guide the screw, and can make screwing a process feel more controlled. This is especially important for screwing near an edge or corner or on smaller or thinner pieces of wood, where the pressure the screw applies may simply drive the fibers apart. Instead of simply drilling through, the screw might split the wood alongside the path, or it might push the wood fibers up above the surface of the wood.
Before the drill touches the project, check the spot on the board where the hole is to go. A hole near an edge may split the wood, especially on a narrow piece, or a board made from dry softwood; a hole near a corner may split the corner. Consider moving the screw into the body of the project instead if that will make things safer, and make sure the board has a bit of extra width for the screw to sit comfortably. There are often a few millimeters that will make a big difference between a good and a ruined edge.
The drill bit must also be checked. It needs to be smaller than the outside diameter of the screw so it can still fit through the wood, but it needs to be large enough for the screw to travel easily. If the bit is too small, the wood fibers may just spread apart anyway; if it is too big, the screw will not have enough wood to grab onto. An offcut of wood is the best place to make sure the screw and bit fit each other, as you can then try screwing through it to see if the wood splits, the screw enters in the right way, or it just doesn’t hold onto the wood at all.
A pilot hole that does not go deep enough can still allow the screw’s point to enter and split the wood. A pilot hole that is too deep will allow the screw to come straight out the other side, or split a thin board. You can mark a depth for the drill bit on a scrap piece with a bit of tape and use that same bit on the project. Keep an eye on the depth as you drill and be sure to hold the board steady with your hand or a clamp, so the drill bit does not catch the board or move it when entering the wood.
The pilot holes may be affected by what is beneath the board, too. If the board rocks on the table, if the wood is not smooth, or if the pencil line does not show clearly because of dust, it may make drilling harder than necessary. The board should be brushed off, the line should be clearly visible, and the hole should be drilled in without the drill being leaned to one side at an angle. You do not need the drill to be moving especially quickly. You just need a hole in the board that will allow the screw to travel exactly into the place that was marked on the board with the pencil.
Before drilling the first pilot hole into a piece of wood, ask yourself these four questions: Is the mark far enough from the edge? Is the right size drill bit being used? Is the depth of the hole being controlled? Is the piece clamped and supported? If the answers are yes, drilling should feel less like taking a chance and more like being the next step in a series of well thought-out steps.