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Drilling Deep Pilot Holes photo

Recently, I was working on a simple bench for my mudroom. Since it was held together with just woodscrews, the construction was pretty easy.

In most cases, I drill the holes for the screws in one step with a drill bit and countersink set. But these screws were extra long, and I was a little worried about splitting the wood. So instead of one step, I did it in three, see photo. Here's how I went about it.

Drawing OneCounterbore. Since I planned to cover the screws with wood plugs, the first thing I did was drill a counterbore. It's simply sized to accomodate the screwhead (#8 in this case) and the wood plug.

Shank Hole. Next, I drilled a shank hole. Usually, this hole needs to go through the outside workpiece. But if you look closely at the photo above and drawing at right, you can see that with longer screws the shank hole should be drilled into the mating piece. So to keep everything aligned, I clamped the two pieces together and drilled the shank hole to the depth of the unthreaded portion of the screw. (Remember to account for the counterbore, see the detail in the drawing at right.)

Drawing TwoPilot Hole. After drilling the counterbore and shank holes, the last step is to drill the pilot hole. When doing this, you could leave the pieces clamped together, but unless you have an extra long bit, the pilot hole won't be as deep as the screw.

I decided to play it safe and unclamp the bench pieces first, as shown in the drawing above. (The last thing you want at this point is to break the head off of a screw.) With the pieces separated, a standard bit will drill the pilot holes the full depth of the screw, see the detail in the drawing.

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