Advanced Cuts and Drilling IV - Printing in Plastic: Build Your Own 3D Printer - page 137

Figure 9-2. Part P with the addition of the second largest counterbore hole.
Next, use a 1/4” drill bit to drill the three holes all the way through Part P, as shown in Figure 9-3.
Note that two of these holes are drilled into the counterbore holes. We used Forstner bits for the
counterbore holes, which left a small dimple in the center of the hole that helped us find the center of
the 1/4” holes.